AudioCircle
Audio/Video Gear and Systems => The Vinyl Circle => Topic started by: neobop on 4 Mar 2011, 01:33 pm
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A funny thing happened on my way to the Circle the other day. I stopped off at the Asylum. There was a thread about a guy who got a SL-1200 and a $60 Grado. He said that it smoked his Rega Planet CD, and he is looking for a sub $200 cart for a MM gain stage. Somebody got on and said how a LOMC was better, blah, blah. I told the OP that I thought he should consider the Silver 1, DL-110, AT-7V, etc.
To make a long story short, the discussion got into loading considerations of a MM vs a MC. Hagermann loading calculator was used to plot electrical high frequency resonance of a Shure V15VXMR. Apparently this cart is 1K ohms and 425mH. This results (loaded at 47K/250pF) in a high frequency electrical resonance at 15.44KHz. It was then postulated that this results in a low pass filter that causes a phase shift in the output (even at the preamp out) and it is 120 degrees out of phase at 20K. This doesn't seem right to me. 180 degrees is opposite phase. 360 degrees is back in phase.
I'm not looking for a particular outcome of this question, I happen to prefer MCs usually. I think this analysis is an oversimplification. The effect of a filter on phase depends on the type of filter. Because there are electronics in the signal path after the shunt resistors/cap, I would speculate that this is a design consideration for the preamp. Nobody on the thread seems to have the equipment or program to analyze the output of a phono preamp.
Any thoughts?
http://www.audioasylum.com/cgi/vt.mpl?f=vinyl&m=953118
neo
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A funny thing happened on my way to the Circle the other day. I stopped off at the Asylum. There was a thread about a guy who got a SL-1200 and a $60 Grado. He said that it smoked his Rega Planet CD, and he is looking for a sub $200 cart for a MM gain stage. Somebody got on and said how a LOMC was better, blah, blah. I told the OP that I thought he should consider the Silver 1, DL-110, AT-7V, etc.
To make a long story short, the discussion got into loading considerations of a MM vs a MC. Hagermann loading calculator was used to plot electrical high frequency resonance of a Shure V15VXMR. Apparently this cart is 1K ohms and 425mH. This results (loaded at 47K/250pF) in a high frequency electrical resonance at 15.44KHz. It was then postulated that this results in a low pass filter that causes a phase shift in the output (even at the preamp out) and it is 120 degrees out of phase at 20K. This doesn't seem right to me. 180 degrees is opposite phase. 360 degrees is back in phase.
I'm not looking for a particular outcome of this question, I happen to prefer MCs usually. I think this analysis is an oversimplification. The effect of a filter on phase depends on the type of filter. Because there are electronics in the signal path after the shunt resistors/cap, I would speculate that this is a design consideration for the preamp. Nobody on the thread seems to have the equipment or program to analyze the output of a phono preamp.
Any thoughts?
http://www.audioasylum.com/cgi/vt.mpl?f=vinyl&m=953118
neo
I read the whole thread........some of what one was posting made no sense to me, but I'm certainly not an EE. Most of the other stuff posted seemed only there to pick an argument. I'm thinking along similar lines as you Neo, that the topology of the preamp comes into play here.
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Aside from the abusive nature of some posters, I think it's an interesting question. My thinking is that the designer would probably analyze the output of the phono stage as part of the design process. The electrical high frequency resonance does not show up on the measured output. This was said to be because the load resistor damps it. Makes sense. But a V15VXMR is spec to 25K and has response to at least 30K. I saw a 4-ch forum where they were discussing using it for that, successfully. I wonder if a near out of phase signal can be used to grab the rear channel info at 30K? I have no idea about that, maybe it can.
Maybe I should pose the question to some preamp designers. It would be interesting to have Hagerman's thoughts about this. There are a couple of other manufacturers that have circles here, including Frank Van Alstine.
Yo Wayner, any info on this?
Is that part of the magic of a Grado or HOMCs, low inductance = no phase shift? What's the resistance and inductance of a Grado anyway?
neo
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Grado coils have a resistance of 440 ohms, and the induction is rated at 45 mh. Phase shifting can be caused by high capacitance ICs, phono preamps and even the RIAA EQ curve the preamp MFGR uses can cause it. 30K is something only my dog could hear, I wouldn't get too worked up ion it, unless it's in the 12-15k region. I haven't read the article yet, but is on my list.
Wayner
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CD-4 discrete 4 channel vinyl records had the rear channel information present as an FM subcarrier signal at 30kHz. See wiki link http://en.wikipedia.org/wiki/Quadraphonic_sound#CD-4_.28Compatible_Discrete_4.29_.2F_Quadradisc (http://en.wikipedia.org/wiki/Quadraphonic_sound#CD-4_.28Compatible_Discrete_4.29_.2F_Quadradisc)
The MM phono cartridge has phase-shift present in both channels equally due to the inductance from the coils that are part signal generation mechanism. This phase shift clear down into the mid-band is what mucks up sound of a MM compared to a MC which has much lower inductance and hence much lower phase shift in the audio band. The inductance of a MM cartridge can be canceled out by splitting the signal from cartridge and connecting an identical cartridge body to ground. You are left with a signal level of 2.5mv in the case of a 5mv output cartridge but there is zero phase shift and no electrical resonances. The only limits to the cartridges high frequency extension are mechanical in nature not electrical. I run a modified AT 440ML this way.
Scotty
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And in the end the CD-4 format was a failure, because few, if any cartridges could respond to 30k signals (at least at reasonable distortion levels), and while it sounded good on paper, I think the format went as quickly as it came. Remember, the tiny stylus has to vibrates 30,000 times per second to make a 30,000 cycle wave, and was (and still is) way beyond may cartridge capabilities.
Wayner
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Gents, there's an excellent article on this subject at VE written by an Ortofon rep.
Although it's nearly three decades old, it should be considered required reading.
http://www.vinylengine.com/phpBB2/viewtopic.php?t=33679
Hi Otis,
Thanks for the link. Unfortunately I can't access VE. People were saying something about new filters. Anyway, what is the gist of the article? I assume there is a phase shift. Maybe I'll be able to read it on another PC using a different server.
neo
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Grado coils have a resistance of 440 ohms, and the induction is rated at 45 mh. Phase shifting can be caused by high capacitance ICs, phono preamps and even the RIAA EQ curve the preamp MFGR uses can cause it. 30K is something only my dog could hear, I wouldn't get too worked up ion it, unless it's in the 12-15k region. I haven't read the article yet, but is on my list.
Wayner
Wayner,
I figured that electronics inside a preamp would effect the results of any filter. RIAA EQ is basically a filter(s), I would think. It isn't the frequency response that was of concern. It was the phase shift.
I think the 4-ch thing never really took off. Many people were fed up with formats coming and going, 8 track, El cassette, etc. But we all benefited from it. The shibata stylus was developed for 4-ch to track 30K rear ch info. Soon after, the line trace came along, and then the micro ridge. A guy on another forum has a collection of 4-ch records. He said the rear ch info is easily damaged and they can only be played a few times successfully. I remember Empire ads for 4-ch speakers. They were shaped like cylinders, and looked like end tables. Some had marble tops.
Thanks for your input,
neo
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CD-4 discrete 4 channel vinyl records had the rear channel information present as an FM subcarrier signal at 30kHz. See wiki link http://en.wikipedia.org/wiki/Quadraphonic_sound#CD-4_.28Compatible_Discrete_4.29_.2F_Quadradisc (http://en.wikipedia.org/wiki/Quadraphonic_sound#CD-4_.28Compatible_Discrete_4.29_.2F_Quadradisc)
The MM phono cartridge has phase-shift present in both channels equally due to the inductance from the coils that are part signal generation mechanism. This phase shift clear down into the mid-band is what mucks up sound of a MM compared to a MC which has much lower inductance and hence much lower phase shift in the audio band. The inductance of a MM cartridge can be canceled out by splitting the signal from cartridge and connecting an identical cartridge body to ground. You are left with a signal level of 2.5mv in the case of a 5mv output cartridge but there is zero phase shift and no electrical resonances. The only limits to the cartridges high frequency extension are mechanical in nature not electrical. I run a modified AT 440ML this way.
Scotty
Hi Scotty,
Apparently the phase concern with the V15V goes all the way down to 2K. I still wonder what the phase looks like coming out of a well designed preamp. I would think this would be something that was taken into consideration. They say that phase isn't readily heard by most people, but you would think that when it gets severe enough, info would start dropping out or as you say, muck things up.
That really is interesting about a 2nd cartridge connected to ground. You're turning a 12dB filter into a 24dB filter? I'd guess you have it hooked up at the end of the wires coming out of the arm. Come to think of it, you're running a linear tracker with short wires? I'm sure you've got every one's interest, I'd like to hear more about the physical hook-up and what it does to the sound. How is the 440 modified?
neo
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This phase canceling trick requires that your phono stage have an intrinsically high input impedance exclusive of the ubiquitous 47k input network. Tube and FET input designs have this characteristic. The voltage dividing network replaces the existing input network and you have 10k to ground through the coils in the cartridge body.
My modifications to the AT 440 consist of removing the flip down stylus guard and cutting away the side wings. The remainder of stylus assembly is super glued to the cartridge body. Three layers of 3M viscoelastically damped stainless steel sheets are attached to each side of the cartridge body. Both of these treatments are done to try to render the cartridge as free from spurious resonances as possible. The stainless steel sheets also add some mass to the cartridge as well,I think it was almost 3grams worth.
Movement of the entire stylus assembly relative to the cartridge body is a big problem in most MM cartridges and this problem does not even exist in a good moving coil, ie (no user replaceable stylus).
(http://www.audiocircle.com/image.php?id=43629)
(http://www.audiocircle.com/image.php?id=43630)
(http://www.audiocircle.com/image.php?id=43635)
Audio Technica and Grado are the cartridges best suited for this type of application. These two brands show the greatest similarity to moving coils in their sound-staging and image focus when they have their inductance canceled.
They also have a vivid and dynamic presentation which betters that of some MC cartridges. The secret to the results that can be had from Grados and ATs is in the way spurious motion of the stylus cantilever is controlled by the suspension design used in these two brands. In the case of the Audio Technical cartridges, the cantilever has the same piano wire tie back at the end of the cantilever to inhibit its longitudinal motion that all moving coil designs have. Grado cartridges also control undesirable longitudinal motion quite effectively.
Wayner, I used a JVC CD-4 4DD-5 Disc Demodulator to play my CD-4 records and never noticed any distortion problems in the rear channels. Admittedly the Harmon Kardon quad receiver I was using back in the 70s was probably not state of the art playback but the sound was satisfying to listen to. I think all of the Quad formats failed due to the increased cost and lack of good recordings. Then as now neither multi-channel classical music nor quad encoded prog-rock drives the market place.
Scotty
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neobop,that cartridge body is back in the phono preamp. It is connected to the circuit board by about two inches of OFC 24ga. The cartridge loading is purely resistive there is no roll-off from any filter function due to the network. The high frequency response of the cartridge is now limited only by the the mechanical system involved. The tone arm wiring isn't any shorter than a conventional tonearm.
The arm is a precursor to the ET 1 designed by Bruce Thigpen. He was project engineer at the company that would become Mapelnoll in a later incarnation. The best way to understand what goes wrong due to inductive phase shift is to listen to a record played back with a good low output MC cartridge and then listen to it played back via a MM cartridge. It's kind of like you know right when you hear it, the MC sounds much more correct due to it's vastly lower inductance which results in much lower phase shift.
Scotty
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This sounds very similar to what I have been working on with LD... on the "Near Zero Capacitance..." thread on VE:
http://www.vinylengine.com/phpBB2/viewtopic.php?t=33929
We are using a spare cartridge body as an inductor combined with a resistor in line.
This has 2 effects - 1st it can reduce the resonance peaks caused by the reaction of high inductance MM's (compared to MC's) with cable capacitance, and 2nd F/R and Phase are intrinsically linked - the result is hugely improved phase linearity.
To assist with the process LD wrote a spreadsheet model that allows one to plug in various resistor, cable, and cartridge values to model the resulting frequency response.
If you get rid of the resonance - the phase ends up intact.... (that's the theory anyway)
One of the outcomes of the Ortofon article/research was that it demonstrated how phase starts to go off in concert with resonances - and their solution was and has been since to move the resonant peak as high up as possible to provide phase linearity within the main audio range.
The experiment that LD and I have been working through tries to achieve linear phase and extended Frequency Response ina "standard" MM phono stage with standard cabling (ie 47K + 220pf in the phono stage and then 150pf+ in the cables)
Similar superb results can be achieved with most MM/MI's by dropping total capacitance to below 100pf, and using custom resistive loading (mostly loading between 47k and 100k).
The trouble is most phono stages don't have the facility to drop the capacitive loading on MM setting, and where they have adjustable Resistive loading it is adjustable downwards from 47k, and very very rarely upwards.
If your phono stage can be set to a load of 100k or higher (1M is great!) - you can then adjust the loading to anything you want by using loading plugs (resistors inside a blank RCA plug) plugged into RCA double adapters.
To achieve total capacitance below 100pf usually requires custom wiring - all the way into the turntable/arm. The cable needs to be very low C - and it also needs to be SHORT.
I got my JVC QL-Y5F down to 51pf the impact on almost all MM / MI cartridges is dramatic - once I get my new Phono stage (JLTI with some custom configuration bits added...) I will publish some comparative tracks so people can actually hear the consequence of this type of setup.
In the days of CD-4 Quad - for CD-4 to work required not only a frequency response out to 40k+ but also minimal phase variation within that range.
The CD-4 cartridges achieved this successfully - and the standard parameters were total capacitance 100pf with resistive loading of either 100k or 47k (depending on the cartridge).
The cartridges that achieved this normally had special styli and cantilevers as well - they later became legendary stereo cartridges.... (AT15/20, Empire 1000z/4000D)
Also worthy of note - a low inductance cartridge, has a more extended F/R and reduced phase non linearity for any particular capacitance. - The Quad cartridges were mostly around 200mH to 350mH. Post Quad cartridges raised the inductance as it is "less sensitive to capacitance" - but it also becomes more peaky and F/R is more limited.
The V15V has inductance of 330mH - the post Quad V15Vx is 425mH - guess which one sounds better !
One more thing - people rarely stop to note the parameters manufacturers used when measuring their cartridges for their frequency response charts/specs - a lot of the classic cartridges were measured at 100pf.
And I think these are the very issues which ended up causing the demise of MM/MI from the high end mainstream. If you set up a top MM right (low C, custom R) - it will beat any MC within twice its price.... and a lot of MC's that cost even more.
But a MM requires some custom setup - it usually won't give you that kind out sound straight out of the box on a "standard" setup - where a lot of MC's will give you most of the improvements straight into a "standard" MC setup. (with scope for custom improvements of course)
But this ease of use comes at a cost.... higher VTF, lower compliance, higher noise (caused by increased gain required of the phono stage), and the additional cost of the more expensive phono stage.
I'll step off my soapbox now..... :)
bye for now
David
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There are lots of fascinating aspects to all this that are interrelated. Makes it more difficult to find answers. What's doing what? Like, what's that fuzzy sound coming from, stylus not being firmly planted or phase shift in the treble? I think the reality of a phase shift might be very dependant on preamp topology, but maybe I'm looking at it in the wrong way. I guess I should try to get some answers from preamp designers to see what their take is. Actual info on phase at the output of some phono stages would go a long way to clearing things up.
Perhaps the use of the term filter isn't giving the right approach for the solution. I tend to see it as phase consequences in a loudspeaker crossover or electronic dividing network. Maybe it's more straightforward than that. The plot of the electronic spike looks like a big resonance spike on a woofer impedance curve. Just like the severe consequences of physical resonance in woofers, this is the equivalent for cartridge phase?
I notice a dramatic difference with HO cart performance between my various phono stages. But that too has other aspects of performance that are very different. My AHT has maybe a 50pF shunt capacitor, if anything. But loading any MM at 100K is enough to make my ears bleed. I got best results with a stock 440ML with 1' tonearm cables going straight in and 32K load. Of course I didn't have the cart going to ground with another body. That's really wild. But maybe I would have wound up with a 22K load, LOL.
neo
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I'm not going to the "creating problems" territory, but the whole scope of vinyl playback is in the ears of the beholder. The program material itself is filled with phase shifting. I suspect, by the answers and the questions, that the problem (if it really is a problem) is filled with many still unanswered questions and solutions.
And I ask myself, is phase shifting in the mid to upper frequencies a problem anyway? Certainly it can foul up bass response, but that doesn't' seem to be the target area for the problem.
I was listening to Queen - A Day at the Races last night from a new pressing from Hollywood records (who I'm not really fond of), and the recording was marvolous. Cymbal crash sounded real, Freddy's voice was epic and the performance of the album was surreal. What more could I ask for with any table.
I'm not against further investigation here, but are we splitting hairs again?
Wayner
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Can't argue with that Wayner. You could look at it as part of the old MM vs MC debate. That certainly came up in the Asylum thread as a big reason that MCs sound better. I'm no so sure, and I'm curious about the implications of this. I tend to agree about recordings as well. Sometimes I can hear that an instrument is out of phase on a recording. I guess with mixing boards and instrument amps you could wind up with all kinds of crazy phase angles. How many pots and trimmers can you use and wind up with a phase coherent recording? None, I would think.
I'm not one of those guys that has a handful of audiophile recordings. I go for musical content. Monk is playing Trinkle, Tinkle right now in the background on Pandora Radio. It sounds nice. Kind of distracting when I'm typing, maybe I'll stop. 8)
neo
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Thanks neo.
I'm not trying to take away "scotties" thunder, but I like the way my vinyl sounds on any one of my 8 turntables. Not that 8 is a magic number, and it doesn't make me any TT "god", but from owning lots of tables, I have learned on thing. They sound more similar then different.
Good measures to keep things in balance are using low pf ICs and the other usual stuff. I think this thread will go on for quiet a while, and it should because the topic does offer new and interesting directions to improve vinyl playback. Perhaps we will get it so dialed in that CDs will never have a chance!
Wayner :D
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G'day all, an interesting thread. For what it's worth, as many people here will know, I've long been an advocate of phono stage input resistance optimisation (specifically associated with the Shure M97xE with the 'supplied' stylus), running my DIY phono stages at 62 k and minimal input capacitance from all input sources, so none of this latest new research is 'new' to me!
I personally query whether all the implied complexity is really necessary in practice though. Yes 'physics is physics', however in my personal observation things are not 'that' critical, beyond a certain point. I'm very happy with the performance of my Shure M97xE's running at 62 k through my DIY phono stages and now all I do is listen to music. After all isn't that the ultimate aim? Fair enough? Regards, Felix.
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No offense Felix, but the Shure M97xe is without a doubt, the most boring, unmusical cartridge I have ever heard.
Wayner
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G'day mate, at 'standard' 47 k loading I might agree with you, although it's a matter of personal musical taste. However at 62 k it's fantastic. Try it at 62 k sometime, I think you'll be rather pleasantly surprised. Regards, Felix.
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Hi Felix,
the 62k is important (get's rid of some of the "dullness" - but I think the biggest improvement is the short low C cable and absence of shunt C....
I'm not against further investigation here, but are we splitting hairs again?
Now Now Wayner - you know how important this is...
For the next thread I am proposing a discussion of how many angels can fit on the head of a cartridge screw - and their impact on Effective Mass.
Other variables to be considered - The impact of High Frequencies on angels, effective mass and tonearm resonances... (My Superstitious Aunt does not allow people to whistle in her house.... it apparently chases visiting angels away...)
I think this opens up a whole new avenue of investigation..... there's only so far you can go with hairs!
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Unfortunately the phase shift problem is real and it is one of the primary reasons that MCs exist.
It cannot be effectively addressed in the preamp because each phono cartridge has a unique quantity of inductance that can only be nulled by exactly the same value.
If you can download the pdf doc at this link on the vinylengine website it contains an article from Audio magazine circa 1983 by Kevin Byrne product manager for Ortofon. This article contains a very through discussion of the causes of phase shift in fixed coil cartridges and how audibile the phase shift is. Listening tests were conducted and the sonic effects of phase shift are described.
http://www.vinylengine.com/phpBB2/viewtopic.php?t=33679
How tolerant one is of the sonic aberrations that are caused by the phase shift a fixed coil exhibits is probably a function of what you are used to hearing. Without a direct A/B/A comparison between a MM and a MC it wouldn't be hard to see how the sound of a reasonably flat response MM cartridge could sound acceptable in the absence of a MC reference with low phase shift. This is especially believable when an Audio Technica or Grado cartridge is involved. ATs and Grados have as stable a stereo image as a MC because the cantilever cannot be pulled in and out longitudinally by the frictional forces encountered when playing a record. When the cantilever can be longitudinally displaced when playing a record the sound-stage sounds as though you are listening through a veil of moving water.
The image wavers and and instruments are not stably fixed in space and there is a general feeling of uncertainty about where anything is located in the sound-stage. Except for the aforementioned brands virtually all MM designs suffer from this problem because their suspension consists of a simple donut of rubber or elastomer on the cantilever at the pivot point or yoke location.
At present I am unaware of any alternative to a custom approach to solving the MM phase-shift problem using a second cartridge body in order to have a precision matching set of inductors.
This can be an expensive proposition if you want to use an AT 150 or a upper line Grado and get everything out of it you can. You can easily spend as much as a MC cartridge. When I first went this route back in the 90s you could buy an AT 440 ML for $99, a pair cost me a little over $200 with shipping. Now days a pair of Grado Greens or AT 120Es may be the best way to get a good phono cartridge and a body with a spare stylus for the future.
Scotty
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*Scotty*
ATs and Grados have as stable a stereo image as a MC because the cantilever cannot be pulled in and out longitudinally by the frictional forces encountered when playing a record. When the cantilever can be longitudinally displaced when playing a record the sound-stage sounds as though you are listening through a veil of moving water.
Except for the aforementioned brands virtually all MM designs suffer from this problem because their suspension consists of a simple donut of rubber or elastomer on the cantilever at the pivot point or yoke location.
The above quote has me a tad puzzled. If you're talking about the internal tie wire attached to the back of the cantilever tube, then there are other brands that have it -- I'm thinking specifically of Ortofon, and Stanton/Pickering. I think some Era-IV Shures did too.
In any case are you ascribing the MC sound to a lack of distortion caused by the stylus wobbling in/out on a rubber donut?
Is there any chance you can post amplitude-matched sound samples of your AT440 setup?
Thanks, Otis
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Unfortunately the phase shift problem is real and it is one of the primary reasons that MCs exist.
It cannot be effectively addressed in the preamp because each phono cartridge has a unique quantity of inductance that can only be nulled by exactly the same value.
That brings up an interesting question, I've been meaning to look into. Does the resistance of a cartridge remain the same throughout the frequency range? I think it's usually specified at 1K. I'm not sure how that works with a generator. With a loudspeaker it changes with frequency and is plotted. They use programs to calculate phase between drivers and they use those plots to get more exact results. Driver parameters are loaded into the program.
Series resistance and inductance are used to calculate cart electrical resonance. The cable, shunt capacitance and load resistor are the rest of that circuit. It is a little hard for me to see this in isolation. With all the electronics downstream, I'd just think there would be more to it, like a real filter. A 24dB/octave low pass has an inductor and a cap going to ground. Then it has another set of the same configuration. That changes the phase from 180 to 360.
Think I'll play a record before I get too tired. I found an old Henry Threadgill LP somewhere and it's already cleaned. That should get my mind somewhere else. I better use the Virtuoso though, the AT-95SA has too much resistance.
:wink:
neo
BTW, Thanks Otis for that file.
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Quoted from Otis at 11:22 PM
In any case are you ascribing the MC sound to a lack of distortion caused by the stylus wobbling in/out on a rubber donut?
No,there are certainly a large number of mechanical differences between MCs and MMs other than the lack of of a tieback wire on most MM designs which contribute to a sonic advantage for MCs.
If there IS control of the cantilevers longitudinal freedom of motion, than you have a much better chance of an impressive outcome from canceling out the inductance the cartridge has.
Is there any chance you can post amplitude-matched sound samples of your AT440 setup?
I am not sure what information you are requesting in the above question.
Scotty
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It is not so easy...
Due to having picked up a couple of shop lots of stylus less cartridges, there are some cartridges which I have up to 6 or 7 examples of.
The inductive variance between the channels is SUBSTANTIAL.
I have gone through and measured both DC resistance and Inductance for about 90 cartridges...
Many of them have substantial variances between left and right channel, let alone between different cartridges!!
For example - a series of Technics EPC P24 cartridges:
Inductance (mH) Resistance (Ohm
338 344 571 577
333 342 578 573
334 346 602 574
357 327 574 589
Note that there is up to an 8.8% variance in Inductance between channels let across a series of supposedly identical cartridges.
In trying to find the best inductive match for my Shure 1000e - I settled on an AT SLT96e....
1000e 520/521mH
SLT96e 522/521mH
I am not sure that having a perfect inductive match is quite so critical - Phase remains in alignment as long as you don't hit a resonance - after that all bets are off and phase change varies based on cartridge and electrical design (as shown in the ortofon article)
You can use an inductor (2nd cartridge) to shift or remove the resonant peaks - I suggest you take a look at the model developed by LuckyDog in the thread I linked earlier )You plug in cartridge, and system electrical values - capacitance, resistive loading etc... and it plots a theoretical F/R graph... very handy). Using this technique does NOT require an identical cartridge - it does however require an inductor, and used cartridges are among the cheapest available relatively matched inductors....
By the way - for those in the US the AT440MLa is still an incredible bargain at $99 (from Amazon) - the rest of the world pays 50% extra.
There are tieback wires in a number of styli designs - specifically: The original Shure V15V & V15IV apparently have tieback wires. The Jico SAS styli all have tieback wires - I believe this technique is more widespread than believed among the better Styli.
Once I have finished working through the testing of the current electrical model (and we have adjusted the model accordingly) - I intend to post samples with different cartridges showing the effect of different loadings/inductors etc....
I am doing this as much to test it for my own satisfaction as for anyone else, but everyone might as well enjoy the fruits of that labour.
But one thing that is clear already - you can achieve similar results without a second inductor - all that is required is VERY LOW CAPACITANCE (50pf is good!) and custom adjustment of Resistive loading.
With that you can maintain Linear frequency response with almost any MM/MI cartridge right through the audio range (frequently out to 30kHz or more) - and linear F/R in an "unmessed with" circuit will also provide linear phase response.
As the inductance of your cartridge drops you will find yourself needing less dramatically low capacitance to achieve the result.
A Cartridge with inductance under 400mH should be fine with capacitance of 100pf
bye for now
David
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But one thing that is clear already - you can achieve similar results without a second inductor - all that is required is VERY LOW CAPACITANCE (50pf is good!) and custom adjustment of Resistive loading.
With that you can maintain Linear frequency response with almost any MM/MI cartridge right through the audio range (frequently out to 30kHz or more) - and linear F/R in an "unmessed with" circuit will also provide linear phase response.
As the inductance of your cartridge drops you will find yourself needing less dramatically low capacitance to achieve the result.
A Cartridge with inductance under 400mH should be fine with capacitance of 100pf
Thanks David,
That was exactly the gist of the Cartridge Loading Explained thread at VE. Keep capacitance as low as possible (arm cables + preamp) and adjust resistance loading for flat response. The effect of shunt capacitance is said to lower the actual measured high frequency resonance as well as the theoretical value. If the actual resonance is in the audible band it will usually make the cart sound brighter, while rolling off the extreme high end. If there is an associated phase problem with the electrical res peak, then it would only be made worse with higher capacitance, going further down into the midrange. Some people removed their shunt capacitors with no neg preamp effects, but YMMV.
Another parameter used for the calculations is cart resistance or impedance, which are not the same thing. Although the terms are often used interchangeably, there can be a dramatic difference between the 2 values. For example, I have a spec sheet for the AT-95 series. They all have a DC resistance of 410 ohms. The coil impedance is 2800 ohms @ 1KHz. Wow, that's a biggie. I guess that answers my previous question about the frequency of resistance/impedance. A meter measures DC resistance. Computing Impedance is a more complex.
That brings up an interesting aspect of the calculations for the electrical model. Is it correct to use DC resistance for computing the electrical peak? When you compute the value of an inductor or capacitor in a passive crossover, with its associated frequency/phase implications, impedance is used, not DC resistance. Maybe it's different with a generator, but I really can't see why. If you're looking at shunt R/C in isolation and not part of the circuit topology, then it would seem to be passive. I haven't read the Ortofon article yet, maybe that's covered, and maybe using impedance would only make things seem worse. Impedance is usually a higher value. Maybe the whole thing is a gross oversimplification. The Hagerman model proves to be of limited value when actually trying to find the right load values.
BTW David, The AT-95:
Static cu = 20
Dynamic @100Hz = 6.5
neo
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Yes resistance vs impedance gets tricky - and having the tools to measure this stuff easily is another issue...
Take a look at the Near Zero Capacitance thread on VE - LD is working through some of the issues involved in non-linearity of transformers at low signal levels (eg cartridge with lower leve signals)... it may or may not end up being incorporate into the model
The model as it stands is quite usefull in selecting an appropriate set of loading values.
Impedance vs resistance is not a major issue for standard MM / MC's simply because the load resistance is a whole order of magnitude larger....
And I would suggest that at this stage of development - the model can only give you an indication of an appropriate loading setup - it is after all an electrical model - and does not take into account some of the electro magnetic non linearities, but more importantly it cannot model the mechanical behaviour (cantilever resonance, stylus radius limitations etc...)
So you use the model to get an indication of your desired resistive load - say 65k ohm - then play (measure) with 62k and 68k ohm (and perhaps further afield)
The variation between impedance and resistance becomes largely irrelevant.
I find resistance most useful in trying to identify unlabelled cartridges...
I rekon that a good MM /MI (exotic cantilever, Micro Ridge style stylus) run at 50pf capacitance and properly loaded resistively gives any MC a real run for its money, and does it at half the price or less....
In that kind of environment, some of the other advantages of MM (eg: high compliance) can start to make a difference....
I do not have TOTL MC's to compare against mind you. (A future project...)
bye for now
David
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Another parameter used for the calculations is cart resistance or impedance, which are not the same thing. Although the terms are often used interchangeably, there can be a dramatic difference between the 2 values. For example, I have a spec sheet for the AT-95 series. They all have a DC resistance of 410 ohms. The coil impedance is 2800 ohms @ 1KHz. Wow, that's a biggie. I guess that answers my previous question about the frequency of resistance/impedance. A meter measures DC resistance. Computing Impedance is a more complex.
BTW David, The AT-95:
Static cu = 20
Dynamic @100Hz = 6.5
neo
Impedance rises as frequency rises as a function of inductance. The higher the inductance of the coils the more rapid the rise in impedance vs frequency. Which BTW is the only electrical advantage of "most" MC carts vs MM/MI iron carts.
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http://lgbtlineage.net/ems/MUSIC%20167/impedance.pdf
This might explain some of what you might be looking for Neo on phase shift as a function of inductance and capacitance.
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http://lgbtlineage.net/ems/MUSIC%20167/impedance.pdf
This might explain some of what you might be looking for Neo on phase shift as a function of inductance and capacitance.
Thanks Marc, it's next on my list.
I just looked over the Ortofon article. Plots are from measured phase shift vs amplitude response. If anything, I'd have to say that it validates my suspicion about MM vs MC phase shift. No data was given about cart specifics, apparently that's in an AES article they published, but the MC phase performance didn't look all that much better. The only sound quality attributed to reduced phase shift was imaging. Nothing was said about muddy sound or lost detail that I recall. I'll have to read it again, but it seems that the MCs with the flattest frequency response had the worst imaging. Mechanical damping was used so electrical resonance didn't come into play.
This article was dummied down for general consumption, but the graphs tell a lot about actual phase shift. I'll have to look over the plots again and compare to the plots made from the Hagerman model.
Thanks again Otis,
neo
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Assuming this Ortofon paper is based on actual testing, like it says, there's no doubt that mechanical resonance effects phase behavior. The same MC cartridge exhibited different phase shift when nothing but cantilever damping was changed. We don't have enough information to draw any conclusions about electrical resonance vs mechanical resonance. I suspect, just like in cartridge loading considerations, the electrical resonant frequency is of limited value. The actual high frequency resonance, as opposed to the calculated electrical HFR, is what determines the overall FR. Too much shunt capacitance with a high inductance cart will lower the mechanical resonance. When that mechanical resonance goes into the audible band, is when problems arise. In some cases it could even be seen as a solution if used to augment a deficiency in the treble region. Why else were caps supplied with some carts?
Ironically, the MC cart used for this test imaged best with no damping, however it was said to be unlistenable due to ear bleed type FR. The more the cart was damped, the flatter the response but the imaging suffered more.
I think Scotty is right about eliminating body resonances and securing the cantilever assembly on a MM/MI cart w/removable stylus. The 440 can also be problematic with a high value of shunt capacitance. I have no experience with cancelling the inductance. Maybe you or David, could tell us a little more about your impressions of sound quality with vs without inductance cancellation or reduction.
At this point, I have to say that to a large extent, I agree with Wayner. When I get everything set up just right with my preferred MM carts, it sounds pretty damn good. Too good actually for some of my recordings. I'm not saying better than my MCs. I have a Charlie Parker record, recorded in the '40s. This is a live date. It was recorded on a portable tape machine off a bathroom or hallway monitor. Sometimes a little tone control phase shift comes in handy. :wink:
neo
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What can't be seen in the photos I posted is the bead of super glue I ran at the junction between the plastic mounting plate and the metal cartridge body. While I didn't do any before and after testing for this specific mod I was reasonably sure it couldn't hurt. What I did notice is that the stock AT 440 was a little bright in the upper midrange and it didn't have the correctness of timbre or imaging that my CD playback had.
After the mods to the cartridge and nulling out the inductance problem,the playback from vinyl sounded very similar to CD replay in the parameters of timbre,image size and high frequency clarity. It seemed to me at the time that it was unreasonable that the sound of vinyl should depart that far from a another medium which doesn't have frequency response problems or for the most part high frequency phase shift problems.
I figured if I tried to optimize the system for the nonlinearities present in the vinyl replay then the CD playback would be very screwed up. When the phase problem was eliminated from vinyl playback it was like having your cake and eating it too. I had the same freedom of coloration that I have from CDs and no digitius which is present at times in some digital sources.
I am of the opinion that when vinyl and digital replay are both free of gross nonlinearities they should sound very similar in many ways. I don't think that you should have to optimize your system for one medium to the detriment of the other.
Scotty
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I'm sure the body and stylus mods made a significant difference. One of the biggest criticism of MMs is that the practical aspect of having a replaceable stylus, is also a compromise in performance. I never used superglue, but I secure the plastic stylus holder with tack usually. In the case of an AT, the holder can removed altogether. That just leaves the plug, which is the rectangular part that fits into the body. That seems to sound better. Body Vibrations aren't transmitted through the holder. Your body is damped with the 3M stuff so this is accomplished in a different way, perhaps better. There's no chance of the cantilever moving when it's glued in. Although it could be glued in without the plastic wing. There's a thread a few pages back about the AT-95 and the Clearaudio MMs. AT is the OEM for these. The plugs are the same and styli can be swapped if the holder is cut away on the 95 stylus. I even potted, and mounted an aluminum top plate on the 95.
All this does make it harder to sort out exactly what's doing what. The 95 and 440 have a different character, frequency response, etc, so different sounding improvements could be realized with the same type of mod.
(http://www.audiocircle.com/image.php?id=39783)
(http://www.audiocircle.com/image.php?id=39785)
neo
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Assuming this Ortofon paper is based on actual testing, like it says, there's no doubt that mechanical resonance effects phase behavior. The same MC cartridge exhibited different phase shift when nothing but cantilever damping was changed. We don't have enough information to draw any conclusions about electrical resonance vs mechanical resonance.
I take that back. Further examination of the actual FR response vs phase reveals some interesting conclusions, that I think are a safe bet. The situations where electrical parameters are a factor appear to be with high inductance (MM) carts. The 5 unnamed carts that were tested had phase anomalies that extend into the audible band. Without specific info on the carts in question, it would be imprudent to guess about much more.
There were also 4 plots of the same MC-200 LOMC cart, with varying amounts of mechanical damping. The phase reversal peak coincides with the response peak around 29KHz with the undamped version. The electrical model would put that somewhere, orders of magnitude higher. It appears that the electrical model just doesn't come into play. This would make sense because the inductance is typically so low that it's just not a factor. What is a factor however, is the mechanics. The undamped version had an extreme phase angle associated with the peak at 29K. The phase shift did not appear to go down below 20K. The cart was said to be unlistenable though, in the undamped version, due to the FR. As damping was added to the suspension, the FR flattened out. The phase peak went higher in frequency, and the phase angle also flattened out. Because the phase angle also was flatter, it now extended into the audible band. When the cart had FR of + 2 to 4db @ 20K, the phase shift extended down to 7 or 8K.
neo
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Some of us here at VC participated in a VE thread called Cartridge Loading Explained. Although our posts are probably no longer there, most of us gained insight about loading a cart. The OP, CarlosFM, used a computer program, Spice I believe, to model electrical parameters and predict FR. This was more accurate than using Hagerman's electrical resonance calculator. Whatever, it turns out that it's actual FR that's important for loading, and electrical resonance is meaningless. Values of inductance and capacitance give an idea of what's going on and how to deal with it. It's the mechanical or actual resonance that is affected by inductance/capacitance. That's what is important. The way it can be affected is by lowering the frequency of the mechanical HF res.
I know all this sounds unnecessarily complicated for many. Bear with me, cause the practical aspect is a whole lot simpler. As a general rule, keep the capacitance load on HO carts as low as possible. If you're using a HOMC or a HO Grado, it isn't as critical. So, long cables from your table to your phono pre are not recommended. This will add to the shunt capacitance. If there is a switch or user selectable capacitance on the pre, use the lowest setting. If you're using a very high inductance cart, you might have to change the preamp load resistance to a higher value, for better performance.
Previously, Felix said that he uses 62K to load a stock M97. Why? That load will address the dip in the FR in the lower treble and yield a flatter response. Using a higher load than 62K will make the response curve jagged and the upper treble too bright. This was confirmed by actual measurements by a VE poster named Werner. He's a reviewer at TNT an an EE or something. BTW, he also said that electrical resonance is worthless for loading calculations.
The M97 is a perfect example of a high inductance cart with somewhat dull response. It's not only current, but an upgraded stylus/cantilever, the Jico SAS, is available for it. Users of the M97/SAS stylus report a change in the character of the sound. Loaded at 47K it no longer has the treble dip. Why?
It's the mechanical aspects that are the overwhelmingly biggest factor in determining frequency response.
neo
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Based on the Ortofon evidence, I think it's indisputable that the mechanical HF resonance is what determines phase shift with the MC200. In the commentary it says that typical undamped MCs have amplitude response that begins to rise around 5KHz, goes to +8dB @ 20K, and peaks at +15 to 18dB at 25 to 28K (mech Res F). I suspect, that is the case with virtually all MCs. Resonant frequency can vary depending on moving mass and stiffness, but there are real world limits. A mechanical res F @ 28K is vibrating 28,000 times per sec, as Wayner reminded us previously. The amount of phase shift at res F is severe, 180 degrees. It's only has 10 to 15 degrees at 20K (undamped).
There are plots for 5 unnamed MMs that suggest a similar scenario regarding phase shift. Without specific info on the carts, we can only guess about the effect of inductance. The commentary said that mech res F was lower due to greater moving mass, and that inductance/capacitance was a factor. The MMs typically employ more damping which increased phase deviation. But, looking at the plots, there is no 180 degree phase reversal within the audible band as suggested by plotting the electrical resonance. The peak, which would correspond to 180 degrees, is off the chart, either due to frequency and/or amplitude limitations. Note: That was the case with most MC plots as well.
The phase vs frequency of the MMs showed greater deviation than the MC200. It did extend down to 1 or 2K on some, where the MC had a worst case shift of + 20 degrees at 10K. Listening tests suggested that imaging was the only thing effected, FWIW.
neo
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On the subject of the audibility of phase issues...
There is a very good article by Robert Everest Greene @ http://www.regonaudio.com/HighRomanticism.html
It is focused on classical and more specifically Romantic music (of which I am a fan)...
an extract from that article:
Here we encounter one of the great myths of audio, that transient behavior is the best indicator of musical quality. Ironically, it is quite true mathematically that perfect reproduction of impulses requires perfect reproduction of everything else (in a zero-distortion system, free of non-linearities). But, in listening terms, the ear/brain is more sensitive to sustained sonic errors.
There is in fact evidence accumulating that this is true even of phase behavior, not just frequency response. In visual, graphical, mathematical terms, phase non-linearity has dramatic effects on the shapes of transients. But these effects have very limited audibility. What is more audibly obvious by far, according to recent evidence, is the effect of phase non-linearity on complex sustained music, e.g., choral singing (c£, the research of the audio group at Essex University).
I have been doing some searches for any information on the research at Essex University...so far without much luck.
Phase issues might effectively be inaudible for fans of rock music, and extremely audible for fans of Gregorian Chant....
Bye for now
David
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David,
Very interesting article, thanks.
As I was looking over the article I couldn't help but think of tonality in general. Since the classical period, halls have gotten bigger and tuning has gotten sharper. Middle A at one time used to be 400Hz. Now it's 440.
neo
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The link for the Ortonfon article, once again:
http://www.vinylengine.com/phpBB2/viewtopic.php?t=33679
If anyone is an AES member, the paper was presented at the 71st AES convention, reprint #1866.
Looking at the actual phase nonlinearities of MC carts, they are caused by damping the moving system or suspension. Electrical parameters don't come into play (for phase) because of the low inductance. Some LOMCs have as little as 11 or 12 turns of wire, as opposed to 2000 or 3000 turns for some HO carts. If the mechanical resonant frequency is high enough, there will be no phase nonlinearities in the audible band for an undamped MC. However, damping is necessary to correct the frequency response. When the MC200 is damped for FR of + 1.8dB @ 20K, the phase deviation begins at 7 or 8KHz. Most of the phase deviation will be in the overtone region. The primary frequency of a cymbal usually is around 12 or 13KHz. Anything above that is in the hearing test range, but is said to effect our perception of tonality.
It would be interesting to have specific info about the MMs. In the phase vs amplitude plots, it appears as if mechanical resonance is also the primary cause of phase anomalies. It is suggested in the commentary that inductance/capacitance is also a factor. They exhibited phase shift starting around 1K to 4K. There were 5 examples of different carts. They all had greater phase shift than the MC. It was suggested that the primary cause was the necessity to employ a greater amount of damping.
Damping the suspension seems to be the primary cause of phase nonlinearities in all carts. If phase is linear, it will coincide with amplitude response. Using the lowest amount of shunt capacitance possible with high inductance carts, will help eliminate electrical parameters from contributing to phase shift. It would be hard to go much further with the information. If a cart has a higher mechanical resonant frequency, it should exhibit better phase linearity. The more damping used, the greater the phase deviation.
neo
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Interesting new (old) stuff...
an AES paper presented by some of the Engineers at JVC in the 70's
http://www.vinylengine.com/phpBB2/viewtopic.php?t=35852
They tested 150 cartridges.... and found the ones designed for Quad to be very phase as well as amplitude linear....
They show some sample phase graphs of "typical" MM, MI, MC and "Condenser" cartridges.
An interesting read.... just wish we had access to the data on the 150 cartridges - I bet a few of them are our current highly desirable classics, and that info has never been published.
bye for now
David
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David,
I didn't read the paper, but the conclusions would be consistent with the Ortofon paper - response/phase measurements. It's undoubtedly the high frequency resonance that determines the primary phase nonlinearity. 4-ch carts had to have usable response past 30K. Companies like AT also seemed to keep the inductance very low.
Many of the MM/MI classics were developed after quad died out. Higher output was considered desirable. Of course inductance went up along with output. The shibata tip was developed for quad. And I think the fine line or line contact was developed just after. All the micros came much later. I believe VDH invented the microridge in the '70s. AFAIK all quad carts had shibata or .2 x .7 elliptical tips.
I suspect that too much credence is given to the implications of moderately higher inductance. If response is extended, then another 50 or 100mH isn't going to make all that much difference IMO. Carts like the 881, V-15, 20SS, 170ML, F9 Ruby, etc all had inductance in the 400 to 500mH range, I believe. Maybe a couple of the classics had somewhat higher inductance. It's the ones with inductance in the 600 to 900mH range, and even higher, where you can really hear it, especially if response isn't all that extended.
neo
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Hi neobop, and all,
I've been lurking here since joining yesterday! Great to cross paths with great mates from other navigations!
I have not yet read the thread, so this question may have been answered. In what manner is phase shift audible at home? Is this the issue? I have not experimented extensively with this BUT actually ran into an intriguing situation.
My new and ultra inexpensive Ortofon Omega cartridge shows "out of phase" behavior which is different from ALL other cartridges I've tried on the Shure TTR-117 (ERA V) test record.
It is the "phasing" band on the record, where the announcer states "My voice is recorded in / out of phase, and should be heard...thusly".
I ALWAYS listen to this band over headphones. It is unequivocal...never fails! The "in phase" phrase :oops: is always heard coming from the top of the head, very well focused and centered. But the "out of phase phrase always comes from halfway to the rear of the head...you might say at 45 degrees towards the rear of the head.
But this ortofon! Confounded fellow! The "out of phase" message comes from fully to the rear of the head, or 90 degree difference as heard over HEADPHONESS No other cartridge has behaved this way in about 30 years of listening to the band.
Implications? I have not yet experimented...sorry :oops:. But if this is of any use, please say so, and I will experiment. Even more, I am willing to send the cartridge to neobop's studio for actual audition of this phenomenon.
Great to be back in this company, and let me know,
bauzace50
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B50,
Welcome to the monkey house my friend. Seems like old home week around here. Maybe new home week!! 8)
This thread is an exploration of nonlinear phase behavior. Specifically, LO carts vs HO. No actual testing was done. I have no equipment to test phase behavior on this level. Most of the conclusions are based on an old Ortofon paper that showed phase vs amplitude plots for 5 MM carts and the MC200 with varying amounts of damping. This was done with an accelerometer and precise measurements of the actual output.
Over at the Asylum it was suggested that Hagerman's electrical resonance calculator could be used to plot phase deviation in carts. Hagerman never said that, AFAIK, and it turns out they were wrong. It was also suggested that phase deviation is one of the primary reasons that LOMCs tend to sound clearer, more transparent etc. It could be a factor, but is nowhere near as different as they suggest.
What's an Ortofon Omega? I went to their site and saw no Omega. Knowing you, it's probably an A-90? Anyway, I've never used that test record, but it seems like 90 degrees actually yields 90 with the Omega. My guess is that it has far superior separation/crosstalk. Blending the channels would reduce the effect. I would imagine the imaging with this cart is uncanny. It would tend to image the way the recording is cut, w/o the blending? What are the separation specs, vs frequency?
Last year I actually got a test record. It's the Analogue Productions one. Peter (Soundsmith) suggested I should get it for azimuth. But I don't seem to have a problem doing it by ear. I haven't gotten around to opening the record. LOL it's still sitting there.
Glad you're here buddy,
neo
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Hi neobop,
thanks for your comments! The Ortofon Omega is a very INexpensive, rock bottom cartridge for guys with USB turntables! I wanted to see what Ortofon could do with $30. price, and did a 2-member bicycle with it...nobody else seemed to be interested! :roll:. The A-90 is in my Impossible Dream list!
The bicycle consensus is that Ortofon can summon their corporate muscle to produce something good at $30. There is NO audible treble peak (great news for me), but there is some treble grain.
Insofar as its unique phase behavior, I am willing to let it travel for members' experimentation. But my experience with it is entirely anecdotal. No rocket science here, and I'm not sure if this is in tune with your purposes.
If you'd like to put it to some tracks yourself, let me know. It may fit your purpose... can be seen at www.needledoctor.com/Ortofon-Omega-Phono-Cartridge?sc=7&category=971
Regards,
B50
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Ah ha! One of your ridiculously inexpensive carts. Wishful thinking I guess, about the A-90. I have no idea what's going on with the phase thing. Here I thought I had it figured out. The separation isn't particularly good, so maybe it errs in the other direction, toward mono? :duh:
Looks like a lot of cart for $30. Will it take an OM stylus? If so, you could put a Gyger or whatever the OM40 is, on there and have a $300 stylus upgrade. Sounds like something I'd consider. LOL Like my AT-95 adventures. Seriously though, maybe the grain is coming from the bonded tip. The specs are incomplete at NeedleDr. I assume it's a bonded elliptical of some sort. Upgrade the tip and I suspect it will resolve more, but the highs might get a little more aggressive. The OM20 stylus, a nude elliptical might clear that up.
neo
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Ah ha! One of your ridiculously inexpensive carts. Wishful thinking I guess, about the A-90. I have no idea what's going on with the phase thing. Here I thought I had it figured out. The separation isn't particularly good, so maybe it errs in the other direction, toward mono? :duh:
Looks like a lot of cart for $30. Will it take an OM stylus? If so, you could put a Gyger or whatever the OM40 is, on there and have a $300 stylus upgrade. Sounds like something I'd consider. LOL Like my AT-95 adventures. Seriously though, maybe the grain is coming from the bonded tip. The specs are incomplete at NeedleDr. I assume it's a bonded elliptical of some sort. Upgrade the tip and I suspect it will resolve more, but the highs might get a little more aggressive. The OM20 stylus, a nude elliptical might clear that up.
neo
I'm really not sure that the tip being boded is an issue, either alone or part of treble grain. I believe it to come down more to the profile of probably .4X.7, or .3X.7, and the polish there of. The diamond and its bushing really are a low percentage of total ETM. Most of the "tip mass" is the cantilever, followed by the generator. (Magnet, Iron, Coil) The diamond material certainly isn't going into a resonance. The bushing will not itself resinate at the frequencies induced by the grooves. If it did, the bushing and diamond would most likely seperate.
The grain, if the stylus profile is at least hyperbolic, is most likely due to the various bending modes the catilever is exhibiting and undamped nodal points along the tube. One has to look at the price point the cart was built to, and to be able to market at a reasonable profit. $30.00 in today's money, and it actually plays music is quite a feat.
I picked up an ADC QLMlll for the same money for evaluation "elsewhere" What a horrid little wretch that thing is. Dynamic range out the wazoo......no music though. It would probably fit the "senergy" bill for a teenager cranking up AC/DC on his Bose surrounds.
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Neobop and BaMorin,
so, how are phase anomalies audible? The Ortofon paper says that linear phase cartridges somehow sound "clearer?" That's quite a large target area. Could we put a little bullseye on that target, and tighten the definition?
MAYBE, just maybe, one could start by investigating the "image shift" and image focus ( that is, an image describing a large listening area, OR, an image describing a tight focused point?) A large aircraft carrier versus a small racing boat. They both describe hugely different circles while turning.
With the Omega, over headphones ON THE PHASING BAND, I get a tight, small, focused image on top of my head in normal phase. That same small focused image jumps to the rear in antiphase.
Other cartridges describe the rearward image in a larger, more diffuse image...more like a rear ambience than a rear image.
If this seems like one point to begin describing audible differences in phase behavior, seems interesting. Maybe OTHER examples would be more enlightening, and take us to define (tipify) audible examples of various phase behaviors?
don't heed me too much... :oops: You are investigating the measurable phenomenon of phase changes. I am talking about the audible manifestation of those changes.
Regards,
b50
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B50,
You have the audacity to equate measured phenomena with audible consequences? You imply that there could be practical implications? :wink: I must say, I miss the days when I could look at a magazine and see an actual bench test report on a phono cart. The Ortofon article talked about imaging almost exclusively. Asylum conjecture was about transparency and all around clarity, I guess. Even though phase non linearity wasn't usually measured as such, we can probably take a pretty good guess based on performance or specs.
For the record, phase non linearity is about how phase performance differs from overall frequency response, whatever that happens to be. If the balance of a particular cart isn't to your liking, it may or may not have much to do with phase anomalies. But you're right, imaging would be the obvious consequence, as the Ortofon paper described. The higher the mechanical resonance of a cart, the less likely there is to be phase anomalies in the audible band (20 - 20K). So, a MM or a MC with response to 50K, would tend to have better phase linearity. It's physical damping of the cantilever that introduces phase problems. The higher the mech HF res, the less likely it will be to have non linearity in the audible band. The article implied that greater damping was employed in the MMs, and that inductance contributed.
I've read speculation that absence of inductance is the main advantage of a LOMC. But the implication here, is that a moving coil may have a electromechanical advantage as well. When damping was applied to the MC200 for +1.8dB response @ 20K, phase performance was better than any of the MMs and imaging was superior. HF resonance of the MC was 28K.
The unanswered questions are about MM HF res and how much inductance contributed.
neo
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neo,
ha ha ha haaaaa :lol: funny how one expects measured observations to be heard :oops: Non-engineering types, such as me, learn from the discussion! Thanks.
b50
---NOTE: manufacturer Hans Ole Vitus, president of Vitus Audio (Denmark?) worked extensively in hearing aid Research and Development, and later went into audio manufacturing. He is quoted as saying that the ear can detect the smalles phase errors, and we are more sensitive to those than to amplitude differences (The Absolute Sound, April 2011, page 136 "Back Page").
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Now that is interesting. I guess it would depend on the type of error, cause they are usually considered to be the least detectable.
If phase relates to location, then I think it would like a built-in instinct, a necessary survival tool for locating prey or predator.
Another interesting thing about our hearing physiology - we have small hairs or receptors in our ears that correspond to 100KHz. Even though we don't consciously hear past 19K, or whatever, maybe we sense much higher frequencies subconsciously.
neo
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Now that is interesting. I guess it would depend on the type of error, cause they are usually considered to be the least detectable.
If phase relates to location, then I think it would like a built-in instinct, a necessary survival tool for locating prey or predator.
Another interesting thing about our hearing physiology - we have small hairs or receptors in our ears that correspond to 100KHz. Even though we don't consciously hear past 19K, or whatever, maybe we sense much higher frequencies subconsciously.
neo
Even though we don't hear those sounds in a cognitive manner, the waves still shake the ear drum and all attaching parts......those "unheard" tones have to affect the tone we do hear.
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Even though we don't hear those sounds in a cognitive manner, the waves still shake the ear drum and all attaching parts......those "unheard" tones have to affect the tone we do hear.
If we take that a step further, phase information in the unheard region would also have an impact on our subconscious perception. If we look to the animal kingdom, whales use subsonics (to us) to locate and communicate hundreds of miles. Dogs can discern the direction of a dog whistle.
I notice my cat seems to like mellow stuff like Bill Evans or even up tempo acoustic records. If I put on a CD she's much more likely to leave the room, even if it's laid back. I can always get rid of her for awhile if I put on a Crystal Method or ZZ Top CD. Maybe it's just taste. She is very picky, a good mouser though. Last year the score was Babycat - 3, mice - 0.
neo
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Neo,
this is another anecdote, not far from the spirit of the thread, but off the technical side. I used to listen exclusively through the Dynaquad 4-speaker setup for many years. The effects were very interesting and usually enhanced the perception of most recordings I heard. Of course, Dynaquad uses phase differences in order to work at all.
But a few years ago I had to move to tighter quarters ( after I got fazed on occasion of divorce proceedings) and there was no room for the rear speakers.
Now I listen through a "near field" arrangement, and I swear by it! Most impressive, movies with rear channel information are heard frequently as if coming from INEXISTENT rear speakers ( no more Dynaquad here), and my system is strictly stereo (2 front speakers) There is some sort of unintended phase manipulation going on through this "near field" setup, and the configuration of the room...and I don't need fancy black box 4-channel "synthetizers". It's great when I hear pods flying in from the rear, and contnuing to the front in Star Wars.
Phase is a very curious thing.
bauzace50
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B50,
Thanks for sending me that interview with Vitus. That's really interesting. He used to work for Texas Instruments and checked out the research on digital hearing aid development. He said that we're more sensitive to phase differences than amplitude differences. He also said the ear can detect changes we can't even measure. I don't doubt it.
I remember reading a paper by a doctor doing research with deaf people. It was really fascinating. He could measure physiological responses to sound pressure waves. One way these people "heard" was from the impact on the cornea of their eyes. Just remember, next time you close your eyes to concentrate on the sound, you're actually missing something. LOL
They've been able to simulate surround sound from stereo speakers for awhile now. It's interesting that you hear this phase manipulation with near-field set-up w/o the simulation. Amazon sells a Pioneer 610 DVD player (European model) that has a 24/192 DAC built in. It has a USB connection, upconverts for HD, can simulate surround for 2 speakers, and has a feature that brings up the dialogue while reducing the background sounds. Apparently you can adjust it for a particular movie or scene. This is the future I guess. Music will come from servers or be stored on a drive or something. CDs are already obsolete.
Maybe none of it matters. I just saw a show on the history ch about 2012. The Mayan calendar ends at the end of the last 52 yr cycle in their long count. On 12/21/12 apparently the planets line up again. It wasn't that long ago that they did that, but this time our sun will be at the center of the galaxy. No big deal as far as I'm concerned, but how the hell did the Mayans know this stuff? They also said that the Mayan calender is slightly more accurate than ours. If knowledge is the accumulation of learning, we must be missing some. I think I have it figured out though. The Mayans got their knowledge from the ancient astronauts. You know, the guys who built the great pyramid. I wonder what their music systems were like. Probably telepathic.
neo
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neo,
Agreed! Some phase episodes seem crazy. Like trying to find a cricket from the sound it emits. One can actually be seeing the cricket but its sound makes it appear to be somewhere else! :duh: Crickets KNOW about phase manipulation.
One example of phase causing apparent contradictions: the cowboy movies showing a stagecoach running one way, and the wheels appearing to be turning in reverse...similar to stroboscopic weird effects when starting up a turntable with a strobe disc on the platter.
Phase CAN make sound or sight appear crazy sometimes. :cyclops: One need only know what's causing the effect in order to corroborate one's sanity.
Regards,
b50
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Here's an interesting article on human/animal sound localization;
http://en.wikipedia.org/wiki/Sound_localization
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I think most people would agree that having linear phase response is a desirable thing. In addition to the implications for imaging, it would probably impart a general feeling of coherence or rightness about the sound. I wonder if some phase nonlinearity can sound good or better sometimes, than not having it? Considering that most of us like the sound to be a certain way (lush or dynamic etc), we sort of pick our colorations. Not much is 100% accurate, and if it were, would we like it?
Maybe if a treble background sound was brought forward, it might sound good. On the other hand the anomaly wouldn't be selective about what is affected and might sound bad or weird? I guess it could be like having a horn jump out at you more than what's recorded.
This is kind of theoretical and I'm at the point where I don't really know what I'm talking about. If anyone has something to say about this, please do.
neo
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I think most people would agree that having linear phase response is a desirable thing. In addition to the implications for imaging, it would probably impart a general feeling of coherence or rightness about the sound. I wonder if some phase nonlinearity can sound good or better sometimes, than not having it? Considering that most of us like the sound to be a certain way (lush or dynamic etc), we sort of pick our colorations. Not much is 100% accurate, and if it were, would we like it?
Maybe if a treble background sound was brought forward, it might sound good. On the other hand the anomaly wouldn't be selective about what is affected and might sound bad or weird? I guess it could be like having a horn jump out at you more than what's recorded.
This is kind of theoretical and I'm at the point where I don't really know what I'm talking about. If anyone has something to say about this, please do.
neo
Have a read of http://www.regonaudio.com/default.html
Especially the first few articles in the "recordings and reality" section.
One of the points he makes is that mainstream audiophilia is fundamentally flawed, and that the standard setup (not to mention the search for air / space / imaging) are in many cases leading us down a path of an artificial (sonic) virtual reality.
He also points out what it takes and how it is possible to record and reproduce, with substantial accuracy, a live audio event. Not talking about studio recordings, and multimiked / multitracked artificial audio constructs...
But with the right setup it is possible to put oneself at a particular seat in an auditorium for a live performance...
He also points out that both recording technology and methods as well as reproduction technology and methods (primarily speakers) have developed together to create a particular virtual reality, which is in its way effective and pleasing - but it does not and cannot, in that form, reproduce a live performance.
Through the various articles he covers phase, reverberation, speaker setup and positioning, as well as recording/miking methods and their results.
Along with issues such as the acoustic differences between romantic era, pre-romantic and post romantic auditoria (reverberation time, and varying absorbance of frequencies...) - and how particular compositions (even particular instruments) were designed for particular environments..... and how when these are then recorded (emotive language warning) - the "wrong" way, the result is far from the intent of the original composers, and even further (wronger!) from the way they sound in real auditoria.
Very good, thought provoking, articles....
bye for now
David
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David,
Regonaudio always writes good important stuff and is very well respected. Thanks for the link, to be read later on with great expectations!
Thanks,
bauzace50
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I may be sorry I'm entering into this thread but I have a few things to say.
Phase shift is boldly in the topic, and there has been a request for an EE to respond. Let it be known that the RIAA EQ in every preamp I know of is a simple RC network which simply reverses the EQ that was supplied in making the recording. Therefore, there are not phase problems. The phase shift in the recording is undone by the phase shift in the playback resulting in no phase shift at the end of the process.
However, If the cartridge has an untamed resonance in the audio band all bets are off, but this has nothing to do with the phono preamp and the imagined phase shift in it.
Any discussions in the Audio Asylum are best ignored.
PS. 99% of what we call MM cartridges are actually VR (variable reluctance). GE told the truth with their VR series, where did we get off the track. Pardon me, but i just like to call a spade a spade.
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Hi Roger
If I am using the wrong terms, please excuse me, as I am not an EE....
No question about the RIAA EQ and its correcting the recorded phase EQ (spent a lot of time making sure my digital RIAA was phase correct....).
The issue is really with cartridge behaviour...
First the is the reactivity between inductance and capacitance leading to an electrical resonance.
Then there is the cantilever which also has a mechanical resonance.
So far every cartridge I have measured shows signs of the designers using the M-Resonance (mechanical) to balance out the F/R droop generated by inductance/capacitance, and sometimes the use of the E-Resonance (electrical resonance) to fill out and flatten the curve as well.
So taken individually we most likely have phase issues at a minimum of 2 resonance points, plus there may also be some form of phase error as the electrical F/R drops off due to high capacitance/inductance. (not sure of that last one....)
If the cantilever resonance (M-resonance) is beyond the audible range (say 25kHz +) and the e-resonance is also pushed way out through the use of either or both of low inductance and low capacitance - then there would be little or no phase error.
So far I have measured all the following cartridges / styli and all have had signs of M-Resonances within the audio band....
Shure 1000e with M97xE-SAS
AT440MLa
ADC SuperXLM
ADC Digital Series II
Ortofon OM20
Ortofon/Digitrack 300SE
As a result, achieving a flat F/R with all of these requires balancing an electrical HF droop with a mechanical peak.... as a minimum, and depending on the plot, sometimes using a slight E-Resonant peak to fill in a mid-high droop.
I hope I am making sense.... if not I may need to post some actual plots...
It seems that since the mid 70's cartridge design has been going backwards....
In the heyday of CD4 quad, they had to design for minimal phase issues (as the Quad FM decoding was/is sensitive to phase) and the system required adequate response out toe 38kHz...
To achieve this, the classic cartridges tended to be low inductance, required a low capacitance environment (100pf was spec) and a high impendance load (100k). Cantilevers tended towards more exotic designs and we saw the release and use of Ruby/Saphire/Diamond/Boron/Beryllium and other exotic designs - really intended to push the resonance out far enough so it is no longer a problem... (this last is my own assumption).
Current MM/MI practice tends towards high inductance (500 to 700mH seems standard), in a high capacitance environment (phono stage load of 220pf, + standard cables rather than Low C cables = Total of circa 350pf, and frequently much higher).
I would be interested in finding a simple way to actually measure the phase response of the system.... for that it would require obviously some form of test signal (test record), and some form of measurement software to analyse it.
I have software to do this function for room/speaker analysis, but it generates (and assumes the presence of) its own tones....
As an aside - this appears to be less of an issue with MC's due to their vanishingly low inductance.... making capacitance relatively irrelevant, and therefore requiring the designer to control or push out the M-Resonance outside the audio band - probably the reason we see so many exotic styli in the genre. Not to mention that with a megabuck budget it is easier to fit these sort of technologies, doing the same for a $200 cartridge is a lot more difficult!
Bye for now
David
P.S. I am also aware of the VR term - but generically Moving Iron seems to be the term that is best understood for this type of system.... Ortofon, Nagaoka, and Grado all continue to use this, but there are still plenty of true MM designs.... eg: Shure, Audio Technica
Apparently some of the MI/VR type designs also use magnets on the stylus mounting to boost the non magnetic cantilever stub - some of the latest OM and 2M styli seem to do this, and some of the TOTL vintage Empires also had magnets mounted on the stylus shank (but NOT on the cantilever.... so they are still not moving magnet designs.)
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Gentlemen,
the following is not part of "phase shift", but the most recent two posts bring up an old (but still unfulfilled) curiosity...and certainly is the theme for a separate thread.
Are the design characteristics of MM, VR, MI, "Induced Magnet", sufficiently different to make each a unique principle?
Or, are these design differences really a rehash of topology with no performance advantages? Or restating in another manner: do any of these principles have a performance advantage over the others?
@ neobop: not wishing to twist this thread! :oops: This is best posed in its own separate thread.
Regards,
bauzace50
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A different but interesting Pandora's box? :icon_twisted:
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I think these cart types are grouped together because the have high output. After all this is a consumer oriented biz, like all biz, and it's confusing enough.
I think I was speculating near the beginning of this thread about the preamp or RIAA network contributing to phase shift, and the possibility of phase consequences like a crossover. Thanks for clearing that up, Roger.
The Ortofon article on cantilever damping vs phase was a real eye opener. It's the only time I ever saw phase and amplitude plotted together. I based all my conclusions on those plots and text. Ortofon used an accelerometer, mounted on the headshell? Obviously I'm not an EE either. There is a AES paper that corresponds to the article, That should be interesting (1983).
David, I agree with you about HO designs mostly going backward. I suspect biz considerations are mostly to blame, and the near extinction of records. So any company considering the market and long term possibilities might be reluctant to jump into the mass market of phono carts. There seems to be a proliferation of pricey MC designs. Using the same market considerations, this makes sense to me. They might figure that long term, it's fanatical hobbyists sales that will generate the profits, and not the mass market. Many of these carts are like buying an expensive piece of jewelry. It's a hand made item and profits are realized much sooner, if there are sales.
neo
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Thanks to everyone for their replies. My main interest is very low noise preamp design. I see the group here had done a lot of research and thinking about the cartridges which I deeply appreciate.
I would like to read the Ortofon article, see some articles on how mechanical and electrical resonances are used to counteract each other and any pictures of how the real MM cartridges look inside.
I am also happy to answer brief (i hope) questions about noise and other performance issues in preamps.
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The issue is really with cartridge behaviour...
First the is the reactivity between inductance and capacitance leading to an electrical resonance.
Then there is the cantilever which also has a mechanical resonance.
So far every cartridge I have measured shows signs of the designers using the M-Resonance (mechanical) to balance out the F/R droop generated by inductance/capacitance, and sometimes the use of the E-Resonance (electrical resonance) to fill out and flatten the curve as well.
So taken individually we most likely have phase issues at a minimum of 2 resonance points, plus there may also be some form of phase error as the electrical F/R drops off due to high capacitance/inductance. (not sure of that last one....)
If the cantilever resonance (M-resonance) is beyond the audible range (say 25kHz +) and the e-resonance is also pushed way out through the use of either or both of low inductance and low capacitance - then there would be little or no phase error.
So far I have measured all the following cartridges / styli and all have had signs of M-Resonances within the audio band....
Shure 1000e with M97xE-SAS
AT440MLa
ADC SuperXLM
ADC Digital Series II
Ortofon OM20
Ortofon/Digitrack 300SE
As a result, achieving a flat F/R with all of these requires balancing an electrical HF droop with a mechanical peak.... as a minimum, and depending on the plot, sometimes using a slight E-Resonant peak to fill in a mid-high droop.
I hope I am making sense.... if not I may need to post some actual plots...
I've been thinking about this post, David. As another non-EE, I'm still trying to figure out the role of electrical resonance, specifically. I'm convinced that looking at the output of a HO cart as an inductor and a voltage generator at the same time, is not exactly correct. Electrical resonance does not show up on the measured response of carts AFAIK. If you can show me otherwise, I'd be very interested. In examining the Ortofon phase vs amplitude plots, there seemed to be no hint of electrical resonance per se, as having any presence. The role of capacitance/inductance seems to be the curving and extending the phase shift plot. If you look at the plots again you'll see that all primary phase reversal came from the high frequency resonance beyond the limits of the graph. The mechanical HF resonance defined the frequency of the MC phase reversal and I assume the MM also. The undamped MC had phase shift over a very narrow range that didn't go into the audible band. It is mechanical damping that flattens and extends the phase shift. The text implied that MMs require more mechanical damping. If moving mass is higher, this would make sense. I suspect that electrical resonance might define the frequency where this curving/extending of phase shift occurs.
neo
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Hmm well I'm working on identifying the weird bits - ie that part of the response which is not pure inductor/capacitor behaviour
The first chart is a series of measurements of an AT440MLa with system total Capacitance at 60pf and various resistances....
The nice smooth curves are the theoretical modelled behaviour assuming a perfect inductor/capacitor - the jagged plots are the actual measured F/R
(http://www.audiocircle.com/image.php?id=45210)
Here is a plot where the model has been deducted from the measured
(http://www.audiocircle.com/image.php?id=45211)
The difference between the two is that part of the behaviour which is either "electrically imperfect" (or more correctly, which a simple model does not reflect!) - and the mechanical resonance.
Take a look at the graph for 21k resistance...
The mechanical resonance (which is most likely 80%+ of the delta plot) is being balanced out by the inductor/capacitance drop resulting in almost perfectly flat response from 7kHz onwards.
This shows up the mechanical resonance which exists on this AT stylus - somewhere out around 21kHz perhaps (I didn't measure high enough to see the peak and drop off, so I don't know the exact resonant frequency)
It also shows that by selecting a Resistive loading of somewhere around 26 to 30k is most likely optimum for the AT440MLa - that is where the balance between the electrical and mechanical behaviour will result in something as close as possible to a flat F/R.
BUT - the question remains as to what happens to phase?
I still don't have a way of measuring phase - electrically the capacitance and inductance are low enough to avoid a resonant peak.... but the mechanical resonance is clearly there, and will be affective phase.
Here is the same type of test using a Digitrac 300SE (basically an Ortofon engine with a stylus that under the microscope looks the same as an OM30... but half the price)
(http://www.audiocircle.com/image.php?id=45212)
(http://www.audiocircle.com/image.php?id=45213)
In this case you need to raise the capacitance to bring the electrical resonance back, so that you can fill the dip in between 7-10k... again the resonance is clearly there at the HF end....
(http://www.audiocircle.com/image.php?id=45214)
Here you can see that the 45k resistance plot is better....
These are both examples of styli with mechanical resonance at the HF top end.
My SAS stylus has a resonance around 14kHz, Ed Saunders V15 styli have a resonance around 11kHz.
So the optimum cartridge loading is determined by the cantilever design rather than the generator design.
The Ed Saunders stylus has a soft resonance quite low down, to fill out the mid-high dip - as a result it sacrifices some high end (especially in a higher capacitance setup)
The AT & Ortofon styli accept a midrange dip in exchange for more extension in the high end.
There is also the likelihood that moving the m-resonance further up also moves the phase anomalies further up to where they are less audible (and possibly inaudible?).
Choose your tradeoff!
bye for now
David
P.S. the AT440 measurement used a CBS test record, spun at 45rpm with appropriately adjusted RIAA EQ - giving accurate measurement out to around 26kHz
The 300SE measurements were taken some weeks back with HFN test record Pink Noise track - which unfortunately has an anomalous peak in the extreme high end - so the measurements above 16kHz cannot be trusted.... there is in fact a mechanical peak there, but it is exaggerated by a peak on the pink noise track as well... so I need to redo my 300SE measurements. :(
I now do my measurements with either the HFN Pink Noise at 45rpm (which gives me trusted results to 21kHz) or as above with the CBS record at 45rpm
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Jeez David, I was trying to decipher the 1st set of plots. You've got 10, superimposed. Maybe I'll try to magnify it later. It is a really cool thing to do, and I commend you for that. You have 83K and 97K, but you go down to 10K and 21K, then jump to 46K? I'm sure you've read that many prefer 32K. 60pF total capacitance is unrealistic for most. I suspect that if you take it up to 100 to 200pF (as recommended by AT) it would fill in the dip in the lower treble. Then load with 32K and you'll have near flat response.
I think the effect of capacitance/inductance is to lower the HF resonance to augment the treble but to roll off the extreme high end. As you say, the mechanical response is the major factor in determining FR. Loading should be used to compliment the mechanical response IMO. It seems like you approach from the other direction. You only really have mechanical response to work with. Electrical response is so theoretical, it's near worthless. If you have a high inductance cart you know the implications. IMO you should start with capacitance below or at the bottom of recommended range, then find flattest FR with resistive loading. Once you're in the ballpark you can tune both. Most of these big cart companies like AT and Ortofon actually know what they're doing. They might have no choice but to recommend 47K, but I doubt if capacitance recommendations are arbitrary.
Ortofon 2M - 150 to 300pF
AT 150, 440 - 100 to 200pF
Goldring 1042 - 150 to 200pF
Tonearm/cart resonances can also effect your plots and show up as mechanical resonance. I think it's the HF resonance that is of primary concern.
http://www.tnt-audio.com/sorgenti/load_the_magnets_e.html
neo
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I started out having a quick look, and on my first set of measurements it looked like the delta would vary by the same amount, as I doubled the R loading... so I initially selected 10/20/40/80K (roughly) as my values.... then I added 100k due to Raul Iruegas' plugs and the old CD4 quad standard...
My Capacitances are limited by the C loading plugs I've made up so far.
I figured my base capacitance would cover the "low" territory (including 100pf) and then I wanted something that would simulate "standard" loading - most phono stages have 220pf then you add the table and cables... so 300 was about right... and then I wanted a notch higher...
I have it in mind to maybe make up a couple more C plugs for fine tuning. (I need to be able to get very close to the 100pf spec... and then maybe something around 175pf....)
But I've found that this gives me enough data to be able to plug into my model - I use an interpolation of the Delta values added to the electrical model - then I can vary C and R in the model and predict the end result with some degree of accuracy...
I only got this far the last couple of days.... paint is not dry yet!
Now I need to look at some of my prediction/interpolations and try some of them out to see whether the real results match the prediction. (I must say the underlying model maths is LuckyDog's work... the interpolation and delta stuff is mine)
I have completed a test run with the AT440MLa, Signet TK6-440MLa, AT150-440MLa, Shure MT105p-SAS.
And I have earlier data (not as good....I was not being quite as rigorous at the time) which gives me quite a bit of info on Digitrak 300SE, Shure 1000eSAS.
Interestingly, I am finding that the best (flattest, dip is best filled while maintaining F/R extension) is with the TK6.
I expected better from the AT150, but the 440MLa stylus becomes the constraint.
I wonder where the resonance sits an an ATN150 stylus??
In any case it becomes possible with these models and spreadsheets to set a cartridge up for +/- 1.5db worst case.... so far best case seems +/- 1 db primarily due to the low frequency hump. (it is of course only a hump in comparison to the mids/highs)
I have not had a chance to focus in on the low frequency resonance(s) yet....
I am running these tests on a JVC QL-Y5F with servo damping, so they should be relatively controlled.
Also the Shure cartridges have the damper brush - but it makes no difference to that bass hump (100Hz to 500Hz roughly +1db)
And results measured on my Revox TT (linear 4g effective mass, no damping) are showing the same Low/mid hump. - So I suspect these are an electrical rather than mechanical artifact.
At some point soon I will map out some MC's as well.
In any case getting back to the topic at hand - either type of resonance (mechanical or electrical) throws phase off... and it is not clear whether when you cancel out the resonant peak, it cancels out the phase variation - my intuition is that it doesn't - which would mean you might have flat F/R but phase all over the place due to both electrical and mechanical resonances being present.
lots to think about....
bye for now
David
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I beg to differ. Electrical resonance has no perceivable effect on phase response, IMO. I just looked at the Ortofon plots again. You can't argue with measured response unless their methodology was faulty. I doubt that it was.
Although all of the peaks went beyond the top of the chart, they all were at least around 17K as minimum and 1 was obviously well past 20K. If these were centered around electrical resonance, some would probably be much lower. I think CarlosFM had it right in the first place on the VE thread. Inductance combined with capacitance, has the effect of lowering the high frequency resonance. Capacitance also will compensate for treble response dips while lowering high frequency extension. I was hoping someone could come up with electrical model for exactly how electrical resonance fits in, but at this point I wonder if it does.
There's no question that the mechanical aspects overwhelm all other considerations regarding both phase and amplitude response. Stick a beryllium/ML on that 440 and the frequency response sounds nearly flat at 47K, low capacitance. Put a SAS on a M97 and Felix goes back to 47K from 62K with stock stylus. BTW, the 150MLX has response to at least 30K.
http://www.vinylengine.com/phpBB2/viewtopic.php?t=33679
neo
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David,
If I seem outspoken on this subject of phase response, I guess it's in reaction to that Asylum thread. Sorry, moving on....
Your plots of the 440 seem to confirm the "rightness" of user experimentation almost unanimously winding up at 32K. I think it's a safe bet that no one had 60pF total capacitance, so the depression should be somewhat less. This seems similar to Werner's measurements (TNT) of the M97 confirming Felix's use of 62K for better response. The original 440ML OCC was spec'd for response to 32K. The generators of the ML and MLa seem identical. Resistance, inductance are the same. It seems that the OCC had stronger (neo?) magnets and output was slightly higher. The inductance is 490mH @ 1K and impedance (not resistance) is 3.2K.
That JLTI you got looks great. Congratulations!! It should be easy now to load capacitance right along with resistance. Just use a Y adaptor or stack-able plugs. I'm sure we'll get some very cool info in future.
It seems to me that the primary high frequency mechanical resonance is the major determining factor in both response extension and phase behavior. Inductance/capacitance will effect this, but it seems that electrical models are somewhat overrated in this respect except in the case of high inductance carts. I believe the Ortofon has even more inductance than a 440? Actually, 490mH isn't as high as many modern offerings. I think the 2M are around 600. We can see by your plots with the 300SE, what happens to extension. The same thing happens to phase linearity. The lower the HF extension, the lower the phase shift goes. I think you can also see with the 494pF plots just how flawed the electrical model is. Maybe flawed isn't the right word - inconsequential maybe. AFAIK, amplitude response drops off like a rock at HF resonance.
neo
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Not quite...
It appears, that resonances (whether mechanical or electrical) cause substantial phase anomalies...
So wherever the setup is such that the base modelled (pure electrical) response has no "peak" - phase response will nicely follow amplitude response....
BUT: if an electrical resonance (the peaks shown in the model plots) is present and used to balance out the frequency response, then although the amplitude frequency response is (relatively) flat, the phase response won't be...
On the 300SE plot, all the R values above 45K have a resonant peak.... so there would be phase anomalies at all the higher resistances in a 149pf capacitance setup.
Now this is all based on theory - I still have no way of measuring phase.
for situations where the mechanical resonance rise begins above 15kHz and the peak itself is above 20kHz, I think phase will most likely be a non issue in terms of audibility. (at least in situations/setups where there is no electrical resonance)
But based on what I have been learning about real life response - yes the stylus and the mechanical resonance are absolutely critical.
With a stylus with a resonance high up (higher is better), and a cartridge with low inductance, combined with low C cables and load, it is theoretically possible to extend response out well beyond 20kHz.
In actual fact the objective would be:
1) Avoid electrical resonance (limit R load to just below resonance point as max)
2) Extend sufficiently far and tailor the rolloff curve so it provides the inverse of the mechanical resonance - thereby resulting in extended HF response
3) Select a cantilever which places the resonance at 21kHz+, with a relatively steep rise to the resonant peak
To make things more interesting (!?) there is also the midrange droop and some frequency related anomalies that happen when the voltage (signal) drops below a certain point - these are most likely related to inductor core permeability - and are likely similar to the hysteresis curves reflecting magnetic behaviour in tape heads.
Once you start digging into vinyl - the fact that it works at all is pretty miraculous - that it works so well is astounding!
In any case I am starting to meander away from the phase shift topic.
I have made an effort to obtain low inductance MM/MI cartridges (as it extends the electrical F/R.... and makes things easier in combination with adjustable capacitance)- which is not as easy as it may seem.
ADC SuperXLM and ZLM were low inductance, the rest of the XLM/QLM/VLM series (which look identical!) were high inductance.
The ZLM's are usually labelled (and usually expensive) - the SuperXLM's were often NOT labelled other than on the stylus.
So with this 40 year old cartridge, it is pot luck - you buy a cartridge on fleabay... get it in, then measure it - and try again until you get one of the low inductance ones!
The AT12 series in the early days were low inductance - later they moved to higher inductance - but right through both stages they were called AT12Sa... same colour, same look body - only way to tell is to get one and measure it! (AT13/14/15/20's also had early series with low inductance and later with high)
There are other examples out there...
Once you have a low inductance generator, then you need a stylus with the right type of resonance curve and placement....
I have tried with the AT102/120 family (440MLa) - the resonance is too low down the frequency range (as can be seen in the delta plots - which are 95% mechanical resonance... by my guess) - I don't have a 150MLx stylus to test - but that may be an option at some point
The 300SE curve is far closer to my target. (Ortofon has been banging on about phase for a long time... so their design approach may have some synergy with what I am trying to do!)
I did some initial testing with two ADC styli, a Digital Series II eliptical and a SuperXLM - both had very similar profiles to the 300SE.... so the ADC cartridges may be a good match for what I am trying.
I had been hoping that the SAS stylus would be a good fit as well - but at least in its N97xE Version, the resonance is relatively broad, not too extreme (sever db) and located in the high centered around 14kHz (with impact going down to 10k and up to 18kHz.
So although it is a great tracking stylus, it is unlikely to meet my requirements (although it may make a great "stalking horse" in that theoretically the "ideal" setup should sound better....)
And yes I am very happy with the JLTI - it has loading plug RCA's on the back into which I have then plugged metal RCA double adapters - C loading goes into one, R loading into the other.
And yes you are right, once an electrical resonance occurs, the amplitude response curve becomes far steeper after the resonance....
I believe the 2M series are over 700mH, I have an OMP body at around 400mH and most OM's are 460mH (ish)
The Digitrak 300SE is around 520mH (might be the same as an OM Super?)
The Technics EPC-P22/23/24/30/33 series are interesting as they are cheap as chips, readily available and have inductance around 350mH. (I have a HE stylus on the way to try out)
The end result is the sum of the electrical and mechanical response - so both have to be right to achieve the desired outcome.
Unfortunately, there is absolutely no way of knowing the mechanical behaviour of a cantilever from its specifications. - You have to buy it and test it.... so I am on a fishing expedition for appropriate styli - and preferably ones that can be fitted to a low inductance cartridge.
I may of course be tilting at windmills ....
This would be a lot easier if phase measurement tools were as readily available as level measurement tools.
oh well
I'll be off now, I see another windmill in the distance
David
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Not quite...
It appears, that resonances (whether mechanical or electrical) cause substantial phase anomalies...
So wherever the setup is such that the base modelled (pure electrical) response has no "peak" - phase response will nicely follow amplitude response....
BUT: if an electrical resonance (the peaks shown in the model plots) is present and used to balance out the frequency response, then although the amplitude frequency response is (relatively) flat, the phase response won't be...
On the 300SE plot, all the R values above 45K have a resonant peak.... so there would be phase anomalies at all the higher resistances in a 149pf capacitance setup.
Now this is all based on theory - I still have no way of measuring phase.
for situations where the mechanical resonance rise begins above 15kHz and the peak itself is above 20kHz, I think phase will most likely be a non issue in terms of audibility. (at least in situations/setups where there is no electrical resonance)
This would be a lot easier if phase measurement tools were as readily available as level measurement tools.
David
Maybe because you're in your PC making this analysis, phase linearity will be easier to plot somehow. Other than that, AES articles can be purchased, and Ortofon probably describes the use of an accelerometer in their corresponding article. Hopefully there will be a much more detailed description of both methodology and cart specifics.
I fail to see where electrical resonances have any effect what so ever on phase. That's my point. If somehow you get phase plotting capability, I'll be very interested in results. In the mean time, my conclusions are based on the Ortofon measured results, not conjecture. There was 1 primary frequency that was cause of all phase non linearity. That was the high frequency resonance. It appeared as if the HF resonance was lowered by cap/inductance in MM cases. That would be interesting if in fact the primary frequency was the electrical resonance, but it didn't look like that was a possibility.
I think that eventually, you'll need plotting capability to at least 30K, preferably higher. 50K would be better. That way you could really see what's going on up there. You mentioned audibility. The Ortofon conclusion was that it was clearly audible with all carts. It was only the mechanically undamped MC that had obviously superior imaging capability. However, it was unlistenable undamped because of the frequency response. With damping, MC phase shift was extended down to 8 - 10K and imaging was not as good. All the MMs had phase shifts extending lower, some to 2K. None had imaging capabilities that competed with the MC. The MC had a HF res of 28K. My conclusion is, if response is more extended, imaging will tend to be better.
neo
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The AT12 series in the early days were low inductance - later they moved to higher inductance - but right through both stages they were called AT12Sa... same colour, same look body - only way to tell is to get one and measure it! (AT13/14/15/20's also had early series with low inductance and later with high)
David
Must have been why I thought my AT 12Sa sounded much better than my AT440MLa.
(with "normal" 47K)
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Has anyone researched the Kinergistics phono stage that had inductance cancellation as part of the design?
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Wasn't that a MC stage? Apparently it wasn't well thought of. I found this DIY forum that mentions it, among other things. John Curl joins in on the discussion.
http://www.diyaudio.com/forums/analogue-source/32318-current-amplifying-phono-stage-3.html
neo
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I was looking over this thread - it's been a couple of months, and maybe it's time for a progress report. There seems to be a discrepancy between David's statement about mechanical resonances other than the primary HF, causing phase shift vs my contention that the HF primary are the defining cause of all phase shift in both LO and HO carts. I know David is doing some great work measuring different aspects of cart performance. I don't expect him to have phase linearity measurement capability, but a reexamination of some evidence we already have might help.
Why is it that that the measured phase performance shows no evidence of any phase anomaly other than that caused by damping the moving system and primary HF resonance? I think this question defines the problem. It would seem reasonable that any resonant peak might cause a similar or secondary phase anomaly. Maybe not. The primary peak is severe and causes a phase reversal on either side of the peak. There could be other factors as well. Is mud caused by arm/cart resonances or cart vibrations also phase?
All psychics and physicists welcome to respond.
neo
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Hi Neo,
the phase question has not faded from my mind....
I found a test record apparently intended for phase measurement, it was delivered this morning - I have not yet removed it from its packaging and have no idea whether or not it will help shed any light on things!
The physics or resonance peaks is well known (apparently.... from my reading of other people's conclusions!).
In an attempt to remove resonances from the audible range of a cartridge - I have been spending most of my time working on cartridge loading...
Then I started looking at cartridge loading to move resonances "out of harms way" - so to speak - while using digital linear/phase neutral equalisation to provide flat F/R... - With very good preliminary results (how about +/- 0.3db from 80Hz to 20kHz !?! )
Until I get some tools with which to investigate phase - all I can do is focus on methods of tweaking the system that eliminate possible phase issues.
To which end:
1) select a stylus with as high a resonance as possible - so far the best are ADC RZL, Ortofon OM20/30 and AT15/20ss - all have mechanical resonance around 21kHz to 23kHz - all of them show resonant amplitude influence down to at least 15kHz and possibly lower... - so there is a likelihood of some phase anomalies above 15k with all of these - but that leaves the main audio range phase linear...
2) optimise cartridge choice and loading to completely avoid electrical resonance - I believe the EE term is keeping the loading below the critical threshold - while adjusting that same loading to provide as smooth a Frequency response as possible. (so far in every case this has meant raising the loading resistance to as high as possible without passing the threshold - while keeping capacitance as low as possible)
3) Use Digital EQ - keeping the adjustment very "smooth" in terms of the adjusting curve - using pink noise to set the parameters...
I am in the process of making comparative recordings with at least 6 different cartridges each at different loadings/setups and each either with or without EQ... this is a lengthy process to say the least. (each EQ'd setup takes quite a while to get right.... even with automating software, the final touches are manual)
Once I'm done with the recordings I will get into the in depth comparison....
At present my preliminary work was done to ensure that the digital recordings I made are sufficiently high quality that I cannot discern a difference between digital and analogue - got that pinned down a couple of days back. (and very satisfying it is too...)
I have also compared my ADC SuperXLM at 2 different loadings (quite clearly different) to the same cartridge with the same 2 loadings with digital EQ applied - 45minutes careful listening and re-listening to a range of tracks and I cannot differentiate between the two. First setting was with 50pf/83k second was with 300pf/47k. Both met the "no resonance" critical threshold requirements. - I probably need to add a third setting to the mix, one with a distinct electrical peak, then equalised - ie intentionally generate a phase anomaly in the audible range, and see whether that is then audible. (doing that is another afternoon's work....)
Plenty going on in Laboratory Laloum..... (and I haven't even pulled out the ouija board or the crystals!)
Bye for now
David
P.S. the 50pf/80k ADC setup sounds very "airy" wide soundstage, nice!, the 300pf/47k sounds more constrained, shut in, not as nice (all relative it still is a very good sound) - this is the typical standard MM config. The Digital EQ versions sound slightly less airy than the 50pf/80k un-EQ'd version - but still have the wide soundstage, a lot more air, an open sound ... quite lovely really - almost sweet..... looking forward to comparing to my "sweetness" champion the Sony XL-MC104.
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Hi David,
Hmm..... Some far reaching implications with your post - digital EQ and all that. I would speculate that you're not actually measuring the high frequency mechanical resonance (21-23KHz) with those carts. You must be measuring resultant resonance after being lowered by loading? I believe those carts have response well beyond that. I don't think that would be possible if primary HF res was that low. I know that in the past you speculated about response possibly being down 30dB with an AT spec. It just isn't so. A cart like a 4-ch model or any of the older ones might not be flat to spec but will have usable response out to there, depending on load I would think.
Maybe that Sony could be used as a control? Is that a LO? I'm down to 2 MCs, one is a Sony MCXL-2. If you want to borrow it to test, you're welcome to. My Monster however isn't going anywhere. I believe the HF spec on the Sony is published. Your numbers just don't seem right. Another explanation maybe?
neo
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Hi Neo
I begin my adjustments for a cartridge by measuring frequency response....
To do that I use either:
1) HFN Test record Pink Noise run at 45rpm (and adjusted EQ accordingly) - 50Hz to 27hz
2) Denon Frequency Response test 1000Hz to 50kHz
3) CBS STR151 RIAA test record sweep & Spot (40-27kHz - using 33rpm & 45rpm)
I'm also part way through developing some calibration data to correct for the HFN test records innacuracies... the Pink Noise track is inaccurate above 16kHz - as compared to CBS & Denon test records (which are in agreement with each other) and based on comparison of measured results with Miller Audio Research results.
As I recall the CD4 spec aimed at F/R being 15db down at 40kHz
The Sony is a HOMC - I also have a Benz/Empire MC1 (also HO)
I have not put the MC's on the TT in about 6 months, and since before I started measuring in detail....
Recording at 24/96 does limit my top end to 48kHz...
As an example of a cartridge with a low resonance but extended F/R consider the Grado Gold1 - there is a strong resonance at 12.5kHz - but F/R out to 50kHz... it is considered a good CD4 cartridge - limited primarily by its lack of a line contact stylus.
Bye for now
David
P.S. thanks for the offer of the MCXL-2.... but I feel I have sufficient known control points in that I have at least one cartridge that has also been measured by Miller Audio Research (AT440MLa)
Unfortunately they measure only 20-20k
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David,
I must say, I think it's imprudent to speculate about phase shift with secondary resonances unless you can show evidence. For example the Grado. I would guess that there is virtually no phase shift at 12.5K other than that caused by whatever resonance you're measuring. Depending on the magnitude of the resonance, that would be localized to the area immediate to said resonance. This could be caused by arm/cart interface or cart body etc or even your set-up. Primary high frequency resonance would cause anomaly that would be similar (hopefully) throughout model. The only measure results so far indicate that suspension damping causes all phase nonlinearities and they are hinged on the high frequency res peak. I realize you didn't just now correlate with phase, but you did in the past.
I think you need a LOMC with extended HF response to test your set-up. Subtract inductance from results and see what you come up with. I don't know exactly how the signal is terminated. It wasn't long ago you had capability only to 20K. Please don't think of this solely as criticism. I'll be glad to help in any way possible. I also have an Analogue Productions test record. This is also said to be flawed with respect to frequency response, but it has some unique tests that you might find useful. These include RIAA checks and distortion test, and cutterhead set-up. The offer stands if you think either of these might be useful.
Regards,
neo
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Hi Neo,
you are quite right I was implicitly correlating phase with resonances.
The Grado 12.5k Resonance is well documented (take a look at the Miller Audio Research graphs for the Grado Red - and the Grado Gold1 looks identical...).
However due to the ... strange?... electro magnetic structure of the Grado's I have no way of modelling the electro magnetic behaviours and therefore cannot identify whether that resonance is mechanical or electrical.
But I have sought out other tests and reviews of the Grado's and this appears to be common to the entire Prestige series. (the exchangeable stylus Grado's).
Lou Dorren has chose the Grado Gold1 to be the basis of his new CD4 cartridge. This implies it has good phase response above 15kHz. - The fact that this cartridges resonance happens as low as 12.5k may in fact be an advantage in this case due to the rest of the range thereafter not suffering from resonances and therefore being very phase linear - as required for CD4. The frequencies below 15kHz are played back as standard stereo - and less sensitive to phase. (well as sensitive as our ears are anyway... which is not very)
Other than the knowledge that any resonance involves phase anomalies - the Ortofon graphs show a range of different phase variation patterns, related to differing damping methods and intensities.
The theoretical electro magnetic and mechanical models for resonance all show phase anomalies (non linear phase) related to the resonances.
With the mechanical resonances things are substantially complicated by the damping applied (cantilever suspension + additional damping varying by the various designs) - The Ortofon paper shows 4 different phase variances all from an MC200 cartridge cantilever each with a different damping setup (ranging from undamped to very heavily damped).
To maintain consistency in my experiments - I bit the bullet and purchased a LOMM cartridge - a Pickering XLZ - with inductance around 1mH - but it can take any of the stanton 8xx or 9xx series styli - and the pickering XSV/XSP/XLZ equivalents - So I will have both a HO version of this body type and a LO version differing inductances but able to share/interchange styli... so I can more easily isolate and identify cantilever from electrical variances.
I have developed a fairly viable & consistent model for MM/MI performance - it includes the basic LCR modelling, but also a loss factor/slope that allows for the inherent losses in the coils as frequency rises. (this varies by cartridge, but can be measured relatively easily, and is I believe a measure of the quality of the coil structure, materials and lamination).
I also purchased a MC200 quite recently in the hope of using it as a LOMC test subject - but it is the integrated "concorde" version - and it just so happens that it cannot adjust to the relatively short overhang on my JVC arm/Table!!!
So I am hunting for a stylusless MC200/100 of the p-mount or universal mount variety onto which I could plug my stylus. (It is one of those rare removable stylus MC designs, much like the Sony XL-MC's)
It think I have frequency amplitude response measurement under control now - with enough trusted reference points that I have a high level of confidence.
What I need to find is a way to measure frequency-phase variation...
I also have a range of test tracks that should be useable for various types of distortion measurements.
What is the analogue productions test record cutterhead setup track?
I had a serious look at purchasing that record - but at this point, I think I have valid tracks for pretty much everything it offers....
Thanks for the offers - I will keep them in mind
bye for now
David
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David,
Do the wood body Grados also have this resonance at 12.5K? If not, I think you have the answer. The HO woodies look like they have the same generator. Perhaps some non magnetic shield damping would cure it. Part of the Grado magic is having an unshielded body. This is no different really than some people preferring unshielded phono cables, or my AHT phono sounding better in a plastic box. If the woodies still have the resonance, then I would guess it's a physical relationship between coils. They may be having coitus? :wink: Don't snicker, they're a married group.
Peter Soundsmith convinced me that I needed a test record to set azimuth on a retip. I have yet to open the record. It looks really impressive. It was Werner who said that the frequency response or anti-skate track(s) was off.
http://www.analogueproductions.com/index.cfm?do=detail&Title_ID=35532
Let me know if it will be of any use. I know how these expenses mount up.
You're measuring a function of time vs amplitude. If your test set-up doesn't allow for this maybe you could get an accelerometer and do it the old fashioned way. You can probably get one for next to nothing in an old Yamaha subwoofer or similar. I don't know what considerations there are for suitability.
neo
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I honestly don't know about the woodies - have not investigated...
Especially the low output ones!
First issue is if it is electrical related - changes in output (inductance) will shift it
If it is mechanical related - the differing cantilever design (permanent fixed vs removable) is likely to alter the picture as well.
Not sure if it is worth spending time on it...
I don't have an effective model of the Grado electrical response - so I cannot delete the electrical theoretical from the actual to attempt to identify the mechanical resonance....
And because the design is relatively insensitive to loading changes - it makes it harder to identify electrical related resonances (which on HOMM's you can spot by changing the loading and looking for the peak that changes frequency).
With all these limitations - I just can't really gain any headway with the Grado.... I am still recording it as another comparison point in my non-EQ vs EQ testing - but as an analytic exercise.... this one is a bit slippery - I don't have any traction on it.
There was some discussion about some shielding aspects of the designs being different with the woodies vs the removable stylus models ... possibly one of the reasons why Grado moved the upper end to woodies. - Still a fascinating design... indeed a married design !
Yes Werner also warned me about some of the frequency response issues with the HFN test record as well. - Which is why I started cross testing various records and looking for matches and disparities.
The much more tedious spot frequency tests (where you have to measure each spot frequency individually - and there are either 20 or 40 of them) on the CBS records are regarded as a reference... but pink noise can be done almost instantly by comparison!
I can confirm that the HFN tracks are off - and I am getting towards being able to identify exactly how they are off. (I'll get around to that!)
I started hunting for an accelerometer a while back - with the idea of optimising the shelf and plinth using it... but the thought of fitting an accelerometer to a cantilever :shake: - the added mass will affect F/R even if I can succeed in fitting it somehow - and all the accelerometers I know of are way too massive!
I wonder how ortofon did it? (they apparently fitted an accelerometer to the MC200 cantilever... !?!?
I still have to find an appropriate combination of tools (software & test track) that will give me meaningful information - at multiple frequencies between 1k and 20k would be nice!
So many conundrums - so little time...
bye for now
David
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hallo,
here is again the disparity about measured vs observation.
i trust what i hear more than what someone else measures.
i am still not at all convinced that measuring stuff is productive.
with my ears, i can consistently get a better sounding result than using any spreadsheet or basing choices on spectral analysis.
regards,
bas
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Well yes - If tuning a single item...
But what if you are trying to work out a system to use in efficiently optimising any one of say 50 different cartridges....
Doing it by ear will take months if not years.
I recall reading about the 1930's Merc. racers, they had multi-jet injectors - which could only be tuned by one of two or three engineers who did it all by "feel".
Those cars engines were as efficient as 21st century computer controlled high tech motors.... but every time you tuned them you needed one of the top guys anywhere to do it for you.... and now we have systems that allow your local bloke to plug in an electronic dodad, press a button, and when the little green light lights up - he says all done and off you go.
I am not claiming that an experienced ear cannot be used to achieve excellent results - but I would argue that the process involved is a) inefficient, b) unusable by the inexperienced, and c) prone to a wide range of psychoacoustic issues.
That last one (c) is quite pernicious - how many times have you messed and messed again, improved and improved and 6months or 2 years down the track, temprorarily put an old component back in the system (perhaps while something is being fixed or on loan) - and lo and behold it sounds better...
Those incremental "by ear" improvements sometimes focus on one aspect at the unconscious detriment of another.... very very hard to achieve consistent repeatable results!
But yes up until about a year back, I did everything by ear - like most of us.
Then I decided to investigate the tools available in our maturing computerised audio world..... and discovered that things that 20 years ago were only possible in a fully equipped (and very expensive!) lab - could now be done at home with free software....
No longer am I dependent on lab tests in a review - which often don't cover an aspect I am interested in, or don't publish all the parameters of the test, making it non replicable!
There is also a problem in the "I trust what I hear" statement - especially given one of my very first tests which led me down this path.
I took a series of differing cartridges (Ortofon 320u, OM30, Shure 1000e-SAS, Benz MC1, Sony XL-MC104) and started comparing.
They sounded different in a whole bunch of ways (all were using a standard Creek OBH18 Phono stage 220pf/47k + cables pf)
So I recorded the same record using each of them and compared them back to back using multitrack software (one cartridge per stereo track, time aligned so I could switch between them).... yep they all sounded different (I still have the listening notes...)
Then I used the Cooledit analysis to look at average RMS, peak values etc - trying to identify what made them different....
Then I normalised all the recordings on peak values - they all sounded just as different.
Then I normalised all the recordings on average RMS values - and suddenly a layer of difference disappeared !!!!
No editing had been done, no filtering or messing with EQ - all I had done was amplify (or decrease levels) so they all had matching average RMS levels.
Were they still different - Yes they were - but the differences were suddenly made much more subtle.... the ear and mind were being tricked by level differences!
So I then read further on psycho acoustics and the perception of sound, and in particular what amount of level difference is audible - even if one is unaware that the change in sound is caused by a change in level.
One of the Regonaudio articles pointed out that a boost of 0.2db in a very narrow frequency band is clearly audible....
So we can discern variations in level of at least 0.2db and most likely less....
And our hearing can discern these variations within specific frequency ranges - But in most cases it is not consciously discernible as what it is. (psycho acoustics again)
Based on all the above, and other articles, and more lately my own experiments - I am convinced that we cannot simply "trust what we hear". At least not in an analytical sense.
A cartridge or component may sound better simply because the level has been adjusted 0.2db higher - how meaningful is that!!
And the only way to avoid this, is using long term listening methods (install, listen for weeks or months, then go back to the original - do the same, etc...) - where these level variations become irrelevant.
Danger is that our short term sonic memory lasts about 3s - hence the advantage of instant A-B testing for certain types of differences.... some things just get missed otherwise.
If by productive you mean conducive to more listening to music - you could be right, it takes up a lot of time - which could be spent listening.
If by productive you mean conducive to an overall improvement in the system involved - I would disagree with you.... my TT is definitely sounding better!
Still wearing my analytical hat, I would suggest that the difference between the two perspectives is a question of Cost-Benefit analysis with a bunch of value judgements involved in both sides of the equation!
In any case the spreadsheet and spectral analysis does not replace the ears... instead it helps by allowing one to identify specific patterns and measurements that the ear finds pleasing.
It also helps in that you can identify configurations that might work well - without having to spend hours/days/weeks experimenting - which is the point of effective modelling.
And it assists in tuning / level matching comparison tracks so you eliminate the psycho acoustic influences - and can then allow the ear / brain to make a much more effective choice.
In other words all the analytics do not replace the ears - they just help me to use the ears most judiciously and to greatest effect and efficiency.
As an example - my listening to the ADC cartridge described earlier - I chose which loadings to use based on modelling - but then listened to 4 differing configurations - and they were clearly different, even when level matched and EQ'd. I know in measurement terms which of those were the most accurate in reproducing the recorded sound.... but I am not yet sure which of them I prefer to listen to! - The 50pf/80k setup was really nice - but due to its slight upward tilted high end (very MC like) - it may end up not being ideal for all types of music - sort of a tendency to a certain "sound" rather than reproducing the sound of the recording.... The very flat F/R EQ'd version sounded almost as good, and will reproduce much more accurately the soundspace recorded, rather than influencing it - possibly euphonically.
More listening and use of ears required!
Bye for now
David
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8)
P.S. Somehow the accelerometer was said to be on the headshell. I can't conceive of how it could possibly work on the cantilever, or I should say how the cantilever would possibly work. There's a corresponding AES paper. I think these can be purchased. I'll see what I can do.
neo
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Had a look at the Miller Audio Research measurements for a Grado Master Reference... one of the woodies...
In their measurements there is a resonance at 9kHz, and signs of a possible second resonance at around 15kHz.
Unfortunately I cannot draw definitive conclusions as the generator, although of the same overall design, is a very low output low inductance/resistance version - so its electrical parameters are quite different....
There is also a distortion peak at 15kHz - which makes me suspect a mechanical resonance at 15k
There is another distortion peak at 5.5k... ?!? why ?!?
I feel about the Grado's the way I felt about standard MM's about a year back - mysterious box which produces sound - different ones sound better or worse than others.... no understanding of why, where, or how.
Bye for now
David
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David,
Although I know nothing of the test procedures and equipment used for this study, all tests are subject to evaluation or question. As Marc suggests, tests are often done using Grado's recommendation of a med/heavy arm. It's also been implied that bearing design has dramatic implications with these. John TCG says that the cantilever is relatively undamped. You know as well as I, if that is the case the potential for excellence would be great for certain aspects, while making it prone to fault.
I previously stated on this thread that your own detection of resonances should be cross checked and efforts made to confirm. Please don't think of this as being too critical. Your tests and conclusions have considerable weight and influence. I have a feeling that they are much more than you suspect. Keep it up and you'll become the preeminent authority on much of this stuff. In the mean time you could use a couple more arms.
My experience with Grado is limited. Last time I heard maybe the best rendition of Ella Fitzgerald ever. The other problem might have been physical isolation, I'm not sure. I suspect one of those resonances is from the coils, I don't know. Think of Grado as a special case, like putting the cart before the horse.
neo
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dlaloum,What happened to the idea of using the precision inductors the respective cartridge bodies cancel out the effects of inductance in the Grado and Audio Technica cartridges.
Scotty
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Hi Scotty,
It appears to work well...
The original concept was to provide a similar level of flexibility for users with a fixed loading phono stage, as is available for users with variable loading phono stages.... primarily a way of simulating lowered capacitance. - hence my name for it - the Capacifier. (Pacifies capacitance...)
After a series of tests, I sort of put that to the side, and focused on the basic system...
I have a vague feeling it might be doing something a little similar to what Grado's do internally.
The trouble with this stuff is there are so many variables it is easy to get lost in all the possible permutations and combinations.
Full understanding of the ramifications of the capacifier will require A LOT of testing - it doubles the number of variables in the system.
But fundamentally - it provides much better control of the base electrical response of the cartridge in a fixed load setup. - ie: it works.
The capacifier stuff then led me to look closely at the real vs modelled response, and the modelling used in the capacifier allowed me to identify the cantilever resonances ..... which made me realise the importance of the cantilever resonance (and associated damping) in the "sound" of a cartridge.
It is all part of the search for the Holy Grail of vinyl .... the "perfect" cartridge/setup - and understanding what might result in perfection.
What it led me to was that you need to know / understand the cantilever behaviour first - finding the right stylus/damping is the #1 priority (and manufacturer info tells you almost nothing!!)
Once you have found the right stylus - you then grab a cartridge body that it fits onto -and tailor the electrical response around the mechanical response.(your fixed points being cartridge inductance and cantilever resonance)
This is where the capacifier can come in ... it provides this level of flexibility for the 90%+ of users without loading adjustability.
In setting up the electrical parameters - my personal goal is to eliminate or at the very least minimise phase anomalies as well. (hence this thread) - but due to a lack of measurement tools, phase is a bit of a black magic area where a lot of guesswork is used. (!)
Most MM/MI cartridges us a dash of electrical resonance boost to fill out the midrange - this unfortunately has a definite non-linear phase effect on the response.
Which is not to say that the response will be unpleasing! - The Shure V15-II, III & IV are all examples of this approach! (Not the V)
One of the interesting side effects of the capacifier can be (depending on settings) the replacement of a fairly sharp phase non linearity with two very shallow phase non linearities - alongside a substantial extension in top end frequency response - Limiting phase variation to under 15 degrees at two places in the spectrum may be an improvement over a phase variation peak of 90 degrees at a single frequency.
In any case these are just musings....
Currently the base capacifier spreadsheet is available at http://www.luckydog.demon.co.uk/images/capacifier.xls
I've got some working refinements to it that overlay measured results, and also uses measured results to calibrate the model - which then takes into account mechanical resonance ... becomes much closer to reality than the purely theoretical electrical model in the base spreadsheet. :thumb:
But it is very complicated to use. :?
For people interested in custom loading their cartridge, without mods to their phono stage - I strongly recommend the capacifier... non intrusive and it works!
bye for now
David
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"The original concept was to provide a similar level of flexibility for users with a fixed loading phono stage, as is available for users with variable loading phono stages.... primarily a way of simulating lowered capacitance. - hence my name for it - the Capacifier. (Pacifies capacitance...)"
This is a box you plug into that uses inductors like Scotty does? This spreadsheet is used to determine values of inductors? It's hooked to the ground of the phono stage? What's the deal?
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I'm no physicist or Electrical Engineer..
But the circuit is fairly simple...
(http://www.audiocircle.com/image.php?id=48187)
Level 0 is the normal setup R being the phono stage capacitance
Level 1 is added on to it in parallel with R... you now have an inductor (another cartridge is used as the inductor) and a resistor.
This is the capacifier - the effect is similar (not quite the same) - as having low capacitance cable.
Level 2 was an additional development based on having a low capacitance and high resistance initial setup - for that matter it allows more variability as the model does cover varying all the different parameters.
It allows a level of EQ to be applied to dampen any resonances that are there.
For more details you need to read the very long thread associated - in which I tested numerous cartridges with different parameters on it, a couple of people have built and used it with quite a bit of success...
The basic premise for it became a bit redundant for me after I purchased a fully adjustable phono stage, and modded my TT cables to achieve a total capacitance of 50pf. :thumb:
It is relatively simple to build, and it does the job...
There were also discussions around other systems including active ones and applying bias to cartridges.... but none of those were developed - this was built and tested by at least 4 different people that I know of, and two of those are now using it every day...
It is not connected to ground - but to signal ground... I made mine using a p-mount adapter so I could quickly swap "inductors" for different values, and RCA sockets for the R & C values for rapid changes and testing of different values... a sort of lab rig.
bye for now
David
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I'm no physicist or Electrical Engineer..
But the circuit is fairly simple...
(http://www.audiocircle.com/image.php?id=48187)
Level 0 is the normal setup R being the phono stage capacitance
Level 1 is added on to it in parallel with R... you now have an inductor (another cartridge is used as the inductor) and a resistor.
This is the capacifier - the effect is similar (not quite the same) - as having low capacitance cable.
Level 2 was an additional development based on having a low capacitance and high resistance initial setup - for that matter it allows more variability as the model does cover varying all the different parameters.
It allows a level of EQ to be applied to dampen any resonances that are there.
For more details you need to read the very long thread associated - in which I tested numerous cartridges with different parameters on it, a couple of people have built and used it with quite a bit of success...
The basic premise for it became a bit redundant for me after I purchased a fully adjustable phono stage, and modded my TT cables to achieve a total capacitance of 50pf. :thumb:
It is relatively simple to build, and it does the job...
There were also discussions around other systems including active ones and applying bias to cartridges.... but none of those were developed - this was built and tested by at least 4 different people that I know of, and two of those are now using it every day...
It is not connected to ground - but to signal ground... I made mine using a p-mount adapter so I could quickly swap "inductors" for different values, and RCA sockets for the R & C values for rapid changes and testing of different values... a sort of lab rig.
bye for now
David
Level 0, R is resistance or input impedance.
Level 1 has the inductor or cart body in series with the input resistor. This is like Scotty does to cancel the internal inductance. For those who this looks like hieroglyphics, it's different from adding a load resistor. That would look more like the bottom part of Level 2.
If somebody needs additional capacitance, get silver mica ones and load them just like a parallel loading resistor. The burning question is, if you can optimise capacitance on a low inductance HO cart, how much improvement will be realized by cancelling inductance? This is what can be measured in terms of resonance. I suspect all the rest like adding capacitance and/or resistance is mostly for high inductance carts. Notice that resistor R2 is in series with preamp load resistor, not parallel, so it's value would be additive.
neo
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Level 0, R is resistance or input impedance.
Oops - indeed...! don't know why I put capacitance there!
If somebody needs additional capacitance, get silver mica ones and load them just like a parallel loading resistor. The burning question is, if you can optimise capacitance on a low inductance HO cart, how much improvement will be realized by cancelling inductance? This is what can be measured in terms of resonance. I suspect all the rest like adding capacitance and/or resistance is mostly for high inductance carts. Notice that resistor R2 is in series with preamp load resistor, not parallel, so it's value would be additive.
I think the level 2 can be useful with some troublesome cartridges where you are having a problem achieving flat(ish) frequency response.
(I always say flat-ish - as I have yet to see a cartridge that achieves something close to flat f/r!!)
But most recently I have been using Ozone4's spectrum matching capability, in combination with pink noise to provide EQ...
This EQ is very high quality (64bit linear phase maths) - and avoids some of the phase issues present with analogue methods...
But also, best results are achieved (I am guessing and theorising.... and testing this theory) by first setting the cartridge and its load up for a configuration which is as flat as possible while avoiding any electrical resonance.
This can be calculated - and the capacitance & resistance loads chosen for a value that is below the "critical" point (the point at which a resonance starts to develop at the frequency response shoulder), while being as flat as possible.
Then using the Digital EQ to provide the next level of adjustment to boost or depress areas that need it to provide a flatter f/r.
Results so far are very very promising. I am still learning how best to combine these variables... but I am finding that I can take a cartridge that sounds very good and has +/-3db response 20-20k and turn it into a far more neutral cartridge that still sounds excellent and has f/r of +/- 1db and possibly +/- 0.75db
All while maintaining linear phase...
The limitations on the Digital EQ are primarily driven by the imperfections in the Pink Noise tracks I have available to me.... so it is not possible to tighten the EQ parameters with this method beyond what I am getting now I think.
Manual digital EQ could probably achieve a marginally better result, but it would take a huge amount of time for each cartridge/stylus/loading configuration.... I have experimented briefly with manual EQ setting - If I wanted to spend the rest of my life doing this, I could do it - but I don't so I have set it aside...
Once I have this ironed out and working properly, I will be able to compare cartridges with known phase anomalies in the audio range with ones that minimise phase anomalies, while having the amplitude F/R sufficiently similar that differences are likely to be related to phase rather than amplitude.
Of particular interest: Shure M Series with SAS vs AT20ss vs ADC SXLM vs OM30
The Shure M with SAS is a very fine setup indeed - but one with known phase anomalies at 15kHz due to mechanical resonance, and in the standard factory recomended configuration, an additional electrical phase peak at around 10k.
The result is non linear phase from around 5k to 6k.
The 3 other examples all have the mechanical resonance above 20k (so related phase anomalies are limited to above 15k) - and can be configured for a completely linear phase in electrical terms.
Also none of these are what one would call a 2nd rate cartridge!!
bye for now
David
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David,
I'm far from being an EE myself. I know a little something about resistors, caps and inductors from designing X-overs for speakers. Level 1 is exactly the same as a zobel (impedance compensation) network for a driver, except instead of an inductor it's a capacitor. A cap in series with a resistor, put across the drivers terminals, will limit the rise in impedance (as freq increases) of the driver. That resistor will be in parallel with driver impedance above any freq defined by the value of the cap. Sometimes it helps to look at things in a different way. A cart and a speaker are both transducers, only at opposite ends of the chain.
I put out a call on Agon thread for that AES Ortofon paper. It's paper #1866, convention 71. I'm afraid it might have been overshadowed a rant about tubes and ICs. I wanted to discuss carts. Anyway, we'll get it eventually and maybe it will have a description of methodology. I think the accelerometer monitored cantilever movement and compared it to the output? There are other ways to observe phase vs Fr resp. A square wave will indicate phase nonlinearities by seeing the angle of the top horizontal line of the output. The rise time of the cart will be indicated by the left hand vertical line and how far off it goes from being a straight line. Implications of square waves go way beyond the frequency being tested. Times 10, I believe. Another interesting note, no dynamic loudspeaker comes close to being able to reproduce anything that resembles a square wave. An electrostatic speaker is the only type that I know of that actually can reproduce one. A waterfall plot will show decay. You have to be careful of not measuring the preamp, I would think.
Everyone seems to have their own preconceptions and says selectively that certain things don't matter. But do these tests right and confirmed results don't lie or have another agenda.
neo
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I saw that - was wondering what the exact paper was...
I may make some mention of it on that thread to remind people!
I was reading the B&K paper mentioned on that same thread and they talked about exciter/accelerometer based measurement of cartridges and how to do it in the paper - I sort of skipped over it as I could not see a practical use of it for me... (given that I do not have access to those specific type of tools.)
I do have a couple of square wave test tracks now... so I can take a look and see how it comes up.
The trouble is what I am looking for is a nice neat plot of Frequency vs Phase (in degrees) - so a perfect flat line is the target, and peaks/troughs become easily visible.
Although a subjective analysis of a square wave can tell us a bunch of stuff - it doesn't give us a proper frequency/phase plot.
Still looking for a combination of software and test track that will enable me to plot phase F/R...
As a long term user of electrostatics - I do not need to be convinced of their benefits.
2 pairs of Quads left my home about 5 years ago - mostly due to their size...
(I still have a pair of 57's and their matching 303 amp in storage... the 63's and 989's went)
They only left after I had auditioned a pair of (remakably compact!) Gallo Ref 3.1's and found them to be "adequate" if not perfect... (my Quad 989's were a distinct step closer to perfect...)
Their CDT tweeter is not bad... (and from someone who has listened to nothing but ESL's for 25 years that is a bit of an understatement)
Still when it comes to microdetail - things like being able to differentiate seperate instruments within the mass of a symphony orchestra at full crescendo ... the Gallo's don't quite make it... the sound is that little bit more confused.... could it be a phase issue?
It also raises the question of whether most listeners have a setup (and most especially speakers!) on which phase is sufficiently linear to be able to discern phase issues....
in 99% of cases I suspect the answer is no - as soon as there is a traditional crossover network - your phase is more or less stuffed, and that includes most speakers.
Which explains why most people claim phase variances to be inaudible.
Bye for now
David
P.S. the Quad 57's are probably not phase linear either due to tweeter/woofer setup, the 63's on the other hand were measured a number of times, and are lauded for being able to pass a Square wave...
The 57's have a sweeter midrange - but the 63's/989's and later models do everything else better...
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I suspect you're right about being able to discern phase anomalies. except for 1 thing. Ortofon claimed that listening tests showed that they clearly affected imaging. Assuming this is the case, I would guess that a square wave at 1 or 2K would clearly show differences.
The problem with putting too much credence in summaries is that you have to compare to actual results. It was only the undamped MC that was spectacularly superior, but was unlistenable due to ear-bleed Fr resp. When damped for only a slight rise, anomalies went down to 8K. The worst MM under test had problems down to 2K. Phase is certainly an interesting aspect but what is an exemplary MM compared to the MC200?
neo
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I'm not doubting that it would show it...
but it would not measure it.
I have a number of good MM's with resonance at 21k to 23k - the amplitude effects go all the way down to 15k or below...
Question is how far down do the resonances phase effects go... square wave tests tell us a little bit - but not enough...
Bye for now
David
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I'm not doubting that it would show it...
but it would not measure it.
I have a number of good MM's with resonance at 21k to 23k - the amplitude effects go all the way down to 15k or below...
Question is how far down do the resonances phase effects go... square wave tests tell us a little bit - but not enough...
Bye for now
David
A couple of yrs ago it seemed like there was nothing more to say. But I now think, even if you used an accelerometer to measure, it might be difficult to differentiate phase nonlinearities caused by damping from those caused by secondary resonance. The Ortofon plots on the tests previously referred to, didn't seem to show any noticeable anomalies outside of the gradual phase discrepancy caused by damping. I'll have to look at the plots again. It could be that secondary resonance caused phase anomalies were too minor to see, or they don't exist. I don't know if further investigation was persued using square waves. I was under the impression that sq waves would show transient response and amplitude rise or fall, but not phase. Any input on this subject is welcome.
neo
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I did a series of tests generating square waves then passing them through various low pass and high pass filters...
I varied the filter types, so some were digital phase neutral, and others were standard phase changing types...
The square wave output clearly showed the difference between the two filters - even though they were filtering at the same frequencies and same or very similar slope...
I posted the graphs at https://sites.google.com/site/zevaudio/turt/square-waves-and-phase/minimum-vs-linear-phase-sq
Phase issues become quite visible on a square wave trace!
bye for now
David
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Thanks David,
Fascinating stuff, but I have a question. You say, "So as an assistance in working out what and how square waves respond to variations in frequency and phase response, I have taken images of oscilloscope readouts of a 1kHz digitally generated square wave, adjusted with various "phase varying" filters which reflect the typical aberrations found on turntable cartridges"
How do you know that the filters are simulating cart aberrations, and not just reflecting the affects of the filters? There's very little information (that I know of) relating to phase vs amplitude performance in phono carts. The Ortofon paper I've been referring to, is limited to amplitude vs phase at a fixed level, I believe. [Since I brought back this thread, I haven't had a chance to review it, but I think that is correct.] Are you saying that phase aberrations are easily observed when the cart is modulated at one frequency and not under amplitude plotting conditions? If so, does this simulate actual performance?
In the old days, square wave response for carts, was sometimes published along with test reports, in Stereo Review and possibly High Fidelity. Have you seen any of these, and do you have a test record with square waves? Forgive me if you've already posted this, memory fails me.
neo
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Hi Neo,
yes I have a couple of square wave test records...
for the rest - the posted charts were artificial in that the waveform was generated digitally and then filtered digitally - I used the Ozone software for filtering as it allows me both types of filters simply and easily... as to the behaviour of the filters, I have to trust the software vendor!
What I was doing at the time was laying the groundwork, for seeking out phase anomalies in phono cartridges... ie: my collection of examples allows me (and I hope anyone interested enough to read the site) - to identify from a square wave recording of a phono cartridge - whether there are phase anomalies or not.
Of course this would not identify the cause of the phase anomalies.... and some of those could potentially be recorded within the test tracks themselves (!).
Also the cartridge loading circuit (inductance, capacitance, resistance) also has phase impacts... which is why a potentially "ideal" cartridge should have as low an inductance and capacitance as possible.
The RIAA filter used needs to simulate the analogue circuit, as it has to correct the phase anomalies introduced during the RIAA encoding/recording - but potentially and theoretically, it might be possible to thereafter correct the frequency response of the cartridge not using cartridge loading as per standard practice, but using digital filters that do no mess with phase....
I know that this might be considered sacrilege by the analogue purists - but I believe that digital technology is at the level now where good digital equipment is on a par with some of the best analogue kit, and this method has the potential of achieving close to flat phase and amplitude response simultaneously.
My available time for vinyl experimentation however became severely constrained - and I have not taken this project any further (yet).
Based on my square wave charts, you can see from a reproduced square wave test track, how close the reproduction is to the original intent - and as you adjust the loading and/or filtering, you can also in theory identify whether the end result is in fact closer to the ideal... it seems a valid approach - albeit time consuming
bye for now
David
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The RIAA filter used needs to simulate the analogue circuit, as it has to correct the phase anomalies introduced during the RIAA encoding/recording - but potentially and theoretically, it might be possible to thereafter correct the frequency response of the cartridge not using cartridge loading as per standard practice, but using digital filters that do no mess with phase....
I know that this might be considered sacrilege by the analogue purists - but I believe that digital technology is at the level now where good digital equipment is on a par with some of the best analogue kit, and this method has the potential of achieving close to flat phase and amplitude response simultaneously.
My available time for vinyl experimentation however became severely constrained - and I have not taken this project any further (yet).
Based on my square wave charts, you can see from a reproduced square wave test track, how close the reproduction is to the original intent - and as you adjust the loading and/or filtering, you can also in theory identify whether the end result is in fact closer to the ideal... it seems a valid approach - albeit time consuming
David,
I have to wonder about verification of simulated sq wave validity. I assume you can't plug your cart output directly into the PC, so you would have to use a gain stage? Maybe you can it's unclear to me if you're talking about theoretical performance or actual performance using digital filters. I know you've corrected amplitude response with digital filters, but I thought it was after going through your phono pre?
I'm not concerned with analogue purity with this, in fact I think it might have the potential for a better phono stage. Boost the voltage to a usable level w/o RIAA and do everything digitally. High quality ICs are faster and cleaner than discreet components and it could probably be made with capability to dial in your preferred sound, not just in general, but for each record. Is anyone doing this commercially?
Maybe it would be a good time to get back in the audio game. Well, I don't know about that but it seems like it could be killer good.
neo
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I have not taken it the next step
I first had a good theoretical think about it, then did the theoretical exercise of generating square waves and filtering them (all internally within the PC) - providing a reference point as to what to expect...
My current setup had the TT connected to a JLTI preamp, which I had the maker (Joe Rassmussen) modify with an RIAA bypass switch - so I can get straight flat output from it...
Of course the gain stage itself still has an impact... total capacitive loading in this setup without additional C loading is circa 60pf (with some effort I could potentially get it down another 10 or so pf, but I am pretty close to what is possible already!)
I agree that this has the potential for being a "better mousetrap" - but it remains a very technical endeavour due to variances between differing cartridges, styli, and loadings (cable etc...)
So a "turnkey" solution would require a variable gain stage/DAC/Filter, a test track LP, and some software (or perhaps firmware) to do the necessary analysis and then configure the filters correctly.
Weaknesses as things stand today - for best results you have to be careful with the gain and signal/noise - too high and you clip (really nasty in digital!) - too low and you drop into the noise floor.
22 bit resolution seems to still be current state of the art, which provides a S/N of circa 104db - which is just fine when properly calibrated/setup - but if you have a random cartridge, with unknown output, etc...
(mind you, it should be possible to use the same test track LP to "auto set" levels....)
I have toyed with the ideal of getting back into the audio business too - but this might be just too niche.... (and the development costs would never be recovered as a result)
And yes I agree it has enormous potential...
bye for now
David
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Something came up on Karma on the hunt for Precept PC440/550 info. It has to do with absolute phase, but that's not we were really discussing. Specific information is on post #122 and the question posed about DC resistance relationship to impedance, is on the previous page.
http://www.audiokarma.org/forums/showthread.php?t=508578&page=9
"Actually, the DCR is most often the higher of the two figures, very roughly by a factor of two. Look at Stanton, ADC, Empire, Shure (where one of the few exceptions is the V15 II/M91E)."
DC resistance as measured by a meter at a particular frequency is a straight up measurement. With AC, inductance and capacitance (of cart) is factored in, and impedance (@1K for carts) is calculated. I've read that impedance also determines phase angle, so this should impact absolute phase and might be part of the reason for different house sound impressions. I've also noticed that the "best" AT carts have impedance figure close to their DC resistance and don't seem to be aggressive in the highs like some others.
neo
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Something came up on Karma on the hunt for Precept PC440/550 info. It has to do with absolute phase, but that's not we were really discussing. Specific information is on post #122 and the question posed about DC resistance relationship to impedance, is on the previous page.
http://www.audiokarma.org/forums/showthread.php?t=508578&page=9
"Actually, the DCR is most often the higher of the two figures, very roughly by a factor of two. Look at Stanton, ADC, Empire, Shure (where one of the few exceptions is the V15 II/M91E)."
DC resistance as measured by a meter at a particular frequency is a straight up measurement. With AC, inductance and capacitance (of cart) is factored in, and impedance (@1K for carts) is calculated. I've read that impedance also determines phase angle, so this should impact absolute phase and might be part of the reason for different house sound impressions. I've also noticed that the "best" AT carts have impedance figure close to their DC resistance and don't seem to be aggressive in the highs like some others.
neo
Maybe this needs some explanation, although I don't fully understand it myself.
Absolute phase refers to phase like if you have both your speakers hooked up + to - on both speakers. Assuming your electronics aren't inverting the phase, then your speakers are in phase with each other, but absolute phase is inverted.
AT carts always AFAIK, have DC resistance lower value than impedance. This is an explanation of DC vs impedance I looked up:
I think impedance is calculated, not measured.
Standard cart spec for impedance is at 1KHz and such is the case for AT carts. As I understand it, an AC circuit has reactive aspects (capacitance/inductance) and phase is taken into account along with amount of resistance. A DC circuit is purely resistive - no impedance necessary.
Impedance is defined as the frequency domain ratio of the voltage to current. That is the voltage–current ratio for a single complex exponential, at one frequency. The current gets ahead of the voltage and causes a phase shift, defined or plotted by phase angle.
That's the best I can do, I'm not an EE. I would think inductance is the obvious suspect for the difference between DCR and impedance.
The AT-440 DCR is around 770 ohms and impedance is 3.2Kohms. Inductance is 490mH. Some other examples of carts named above, have considerably more inductance and impedance is less than DCR?
If anyone can explain what's happening or verify the above info on Stanton, Shure, ADC and Empire, your input is welcome.
neo
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Don't have the tools at the moment to correctly measure impedance (as opposed to resistance...)
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Can resistance be a higher value than impedance? Seems to me, when factoring in reactance, impedance should always be the higher value.
Maybe measuring parameters at different frequencies will mess up results?
I'm just trying to make sense of the above statement, that the other carts, named above, have DCR > impedance. Maybe he meant something else, but it still doesn't make sense to me.
neo
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Need to read up on electrical theory... impedance does vary with frequency, and with coil design, but I would have thought that ultimately minimum value would be DC resistance and frequency variation would increase that by a variable amount....
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Think I've found the answer, at least to the basic question relating to phase.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/imped.html
From the bottom of the page:
"The units for all quantities are ohms. A negative phase angle implies that the impedance is capacitive, and a positive phase angle implies net inductive behavior."
I don't see how the impedance of a phono cart could be capacitive, which leads back to the conclusion by Carlosfm, on VE. The overwhelming determinate of amplitude response is mechanical.
http://www.vinylengine.com/turntable_forum/viewtopic.php?f=19&t=6674
neo
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Posted this on Karma and VE - but it is relevant to this discussion too so here it is as well!
A couple of things have caught my attention over time...
1) differences between voicing of cartridges (and systems) seem primarily down to variations in frequency response - but may also involve phase effects.
(Note I am not talking about things like tracking ability, dynamics, etc... but voicing)
2) variations in F/R driven by various aspects like cantilever resonance, and cartridge loading, also have an impact on phase - these phenomena appear to be minimum phase... this means that if they are corrected using analogue filters, the phase is corrected at the same time... if they are corrected using digital linear phase filters - the F/R is adjusted, but not the phase.
3) Reading on Ozone5 software shows that the "spectrum matching" feature can be used with either analogue or digital filters... - the spectrum matching allows one to "record" a specified spectrum, compare it to a second recording and automate the required EQ curve to make the two spectrums "match" (or at least approach each other!)
It should theoretically be possible to use a pink noise test track, and the spectrum matching feature to correct a cartridges output for flat frequency and phase response using Ozone5.
One could artificially generate a "perfect" pink noise spectrum - use this as the target spectrum - then record the pink noise test track, and have the software create a custom EQ using minimum phase filters to provide a perfectly neutral end result in both Frequency and phase domains....
I am mentioning Ozone5 here because it is the only software I know of that has this type of feature....
So a theoretical digital phono stage could involve a PC with "matching" software to provide not only RIAA EQ, but also correction of frequency anomalies... (blasphemy I know!)
The end result could be that rather than seeking the perfectly "voiced" cartridge for ones system, one would choose one that matches the TT/Arm best (compliance / mass matching) - with the best possible stylus (low effective mass, high cantilever rigidity, good tracking ability) - and then rather than use crude cartridge loading methods to attempt to get a flat F/R, fine tune things with the Digital phono stage....
Would this allow a high quality budget cartridge to compete with the megabuck contenders? (eg: M97xE with SAS)
There are other aspects of performance that this approach does not cover... but it seems to me that in todays digital world this is the next logical step...
Comments?
bye for now
David
p.s. Although I have Ozone4, I have not bitten the bullet and purchased Ozone5 for experimentation....
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David,
Interesting, to be honest I don't see the point. You don't need a minimum phase(?) equalizer to correct the frequency response on a decent cartridge and the potential to degrade the sound is enormous. I think your JLTI would kill the PC phono. Would sensitivity on the PC be enough? Even if it would, you won't make a budget cart sound like a great one. The information isn't there to start out with.
Must be tough not having your gear at your disposal. Only a couple more months?
neo
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Hi Neo,
in a way I agree with you - my dynavector Karat has perfectly flat F/R and based on specs I believe flat phase/r as well...
But a Karat is a relatively expensive device!
What if the same result can be achieved with a good quality body, fitted with a good stylus (eg: the M97xE with SAS, AT440Mla, etc...) - the high inductance, and the lower resonant frequency of the cantilever can both be compensated for in a much more elegant manner than what I have been trying with cartridge loading....
Properly setting up a cartridge like this, and setting the loading to optimise for neutral voicing (flat f/r) takes a heap of time and effort.... With this approach, you can just run at standard 47k/250pf (or whatever capacitance your setup is at) - and let the relatively automated digital EQ take care of the rest - the tuning process for a cartridge would be under 30min rather than a weekends work.... And the result is likely to be superior...
Of course good quality front end gear is key - a good step up stage (possibly with RIAA) before the ADC - with level control so you can optimise the digital conversion process - then a good ADC, then the appropriate software, and finally a good DAC.
Given the cost of the digital gear and software this is more expensive than purchasing a Karat.... so probably a pointless intellectual exercise unless you already have the gear.
Intellectual exercises are what I am sticking to at the moment until I have the gear here!
All I have at the moment is a TV and a boom box.... (actually squeezebox boom connected to my digital music library on a NAS, with a Gallo sub attached - so it is not as bad as it sounds...)
bye for now
David
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Hi David,
Of course that opens up the possibility of a digital phono stage having the potential to correct other aspects or imperfections in record playback, including the record itself??
If PCphono could correct phase nonlinearities instead of just minimum phase filters for frequency response, it might be flat and have 3D imaging as well.
Imperfect records or pressings could be compensated for by altering the amplitude and phase response - separately. One control for brightness and another labeled hall. Requirements for the cart would be good detail and transient response. Of course impulse noise reduction (click and pop) could be incorporated.
I have no idea how you could accomplish this or if it could even be done, but it seems to me there is the possibility for digital domain correction that goes way beyond what is available for the end user now, whether the source material originates in digital or analog domain. Sometimes I hear phase anomalies in recordings, both analog and digital. Have you ever heard a recording where one mike is out of phase? Correcting something like that would be a little trickier, well, maybe a lot trickier, but you couldn't do much worse than some remastering commercially available now.
I used to have an old Charlie Parker record ('40s) that was recorded off a portable tape machine, monitoring a little hallway speaker. That one and a couple of others were reserved for playback with tone controls. I guess there's only so much you can do if the source material is really poor quality, but we're talking home remastering here, at least to some extent. Right now we're limited to EQ. That, and playing with different cables is about it. You could even save your remasters for future use, but if you change your speakers you might have to do it over. :duh:
If the home remastering lab were available, it might be fun to record you stuff and play with the sound, but I think I'd rather just play a record. Something is lost when an analog recording is digitized and that something is a big part of why records and record playing equipment are still around. Besides, we need a hobby and something to drool over and spend our money on, sort of like classic cars only slightly more affordable. There's no substitute for owning cool tables and a multi-thousand pound record collection.
What kind of electricity do you guys use down under, 120/60? You need a killer DD table like an old Goldmund with a JVC motor. That would be a nice toy to celebrate setting up your equipment again. It would make you forget about this digital phono, at least for awhile. It might be interesting, but I suspect your resources and time could be better allocated. With your new family member you probably won't be able to listen to music while you're on duty, and while you're off duty time will probably be limited. I'll see if I can find you a nice used Goldmund and send you the bill. :thumb:
neo
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I remember auditioning a Goldmund reference in the late 80's at Kostas Metaxas Melbourne audio salon....
Played through his own electrostatic speakers, and amps.... truly wonderful sound.
And the table was (and still is) a technological and engineering marvel :drool:
They are however a little bit rare - and even today still fetch a reasonable bit of change!
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Yea, reasonable bit of change, you're not kidding, last one I saw for sale was $35K. But the Reference is servo controlled belt drive. The 35lb platter was a bit much for direct drive, and they didn't have Harry Weisfeld"s submarine motor.
I was thinking of a Studio or Studetto DD. The ones with JVC motors are the ones to get. Depending on the arm you might have to mod the suspension, could be a little tricky, but doable and much less expensive.
neo
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I like the original linear tracker - wasn't it a modified rabco design? (or was Pierre Lurne involved.... or both?)
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I think it is similar in some ways to Rabco, but a different design. One nice thing is the arm tube is longer than most linear arms. This will minimize record warp VTA anomalies and make VTA/SRA less of a problem in general. That's the T3F arm on the Reference and Studio. The Studietto had an optional T5 linear arm. Mine was w/o the arm and Goldmund supplied two piece aluminum armboards for SME or Linn type mounts. The last table from that era was the ST4 which came with a dedicated T4 linear tracker.
Pierre Lurne designed some of the arms and I think he headed the design teams for the DD tables. I'm not sure of the extent of his involvement, but he later sold a similar linear tracker through his own company. Lurne later abandoned linear trackers for unipivots he sold with his tables at Audio Mecca.
There are a number of interesting interviews in Stereophile and TNT with Lurne. Do a google search and they'll come up. That should make for interesting reading while you mark time.
neo
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I think if I was to setup a TT/Arm (ie: manual rather than the automatic integrated setups I now have...) - I would look at something like a classic JVC or Denon DD with the Dynavector arm - that arm fascinates me, huge mass horizontally and adjustable mass vertically...
Reviews show it working well with everything from high compliance V15V's and Grado's to mid compliance MC's (not sure I've seen a review of a true low compliance cartridge in the dynavector arm).... magnetically damped, versatile, and steam-punk sexy....
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I may be sorry I'm entering into this thread but I have a few things to say.
Phase shift is boldly in the topic, and there has been a request for an EE to respond. Let it be known that the RIAA EQ in every preamp I know of is a simple RC network which simply reverses the EQ that was supplied in making the recording. Therefore, there are not phase problems. The phase shift in the recording is undone by the phase shift in the playback resulting in no phase shift at the end of the process.
However, If the cartridge has an untamed resonance in the audio band all bets are off, but this has nothing to do with the phono preamp and the imagined phase shift in it.
Any discussions in the Audio Asylum are best ignored.
PS. 99% of what we call MM cartridges are actually VR (variable reluctance). GE told the truth with their VR series, where did we get off the track. Pardon me, but i just like to call a spade a spade.
I was thinking about this statement and how it might apply to a strain gauge system with no RIAA correction.
1. Doesn't correct relative phase?
2. No need, maintains phase integrity from midband up, therefore moot?
3. All of the above?
4. none of the above?
5. who cares?
neo
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If the response curve is flat when it comes out of the preamp, then this may be a case where amplitude error equals phase error.
If the strain gauge cartridge can accurately reproduce a square wave then there are no phase errors.
Scotty
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I don't think lack of amplitude error proves encoded phase error is corrected.
If there is encoded phase error, then it would be encoded on the square wave track. I think you're right.
Lets look at the test report. :dunno:
neo
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Most natural phenomena are minimum phase.
If the strain gauge cartridge is also minimum phase (why wouldn't it be!) - then a flat F/R implies correct phase, as the relationship between amplitude and phase in a minimum phase system is symmetrical....
As long as you are not using digital linear phase or maximum phase filters, any mechanical adjustment or standard electrical filtering/EQ will be minimum phase, hence the simple old fashioned flat frequency response is a valid measure of phase correct behaviour.
It sounds too simple to be true, but in this case stick with occams razor....
The strain gauge test report does not look at phase....
But they are measuring an analogue system using analogue (which implies minimum phase) systems...
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That seems right. I was looking at it as a system and the preamp RIAA should be the inverse of cutter head encoding.
The reverse curve is theoretically applied using time constants at 75us, 318us, and 3180us. [2122Hz, 318Hz, 50Hz]
http://sjostromaudio.com/pages/index.php/hifi-projects/147-the-riaa-curve#.U5p4KlIU8dU