[dlaloum]

David,
I forgot to mention - magnet strength effects impedance.  Check out Maestro V2.
http://www.clearaudio.de/_de/tan_Maestro%20V2.php

I am not convinced by the marketing blurb...

An article here on permanent magnet generators http://www.windstreampower.com/documents/EFFICIENCY.doc

It talks about generator efficiency (for power generation) - in our case we want an ultra efficient generator to get the purest possible signal...

Relevant sections from the document:

Magnetic gap - the smaller the clearance between armature poles and magnets, the better the magnetic flux path and the higher the efficiency.

(Note that the Shure V15VMR had the "narrow shank" stylus mounting to allow smaller clearance between poles and magnets... the later unlaminated and more economically built V15VxMR had the wider shank...)

Winding resistance - the lower the internal electrical resistance of the winding, the less energy is dissipated as heat that results from current flow through the winding resistance. Accordingly, the larger the magnet wire diameter in the armature windings, the lower the resistance and the higher the electrical efficiency, but the larger the generator (the same number of turns of the larger wire gauge are required to generate the same output voltage).

(Note: - this is the area of interest and difference between an AT95 and a CA-V1... the V1 has lower resistance and therefore reduced losses, these may well be level related - still researching this)

Some more raw data:
http://en.wikipedia.org/wiki/Magnetic_circuit

I need to read through this reference... and get my mind around the magnetic relationships... but an item of interest:

Most importantly, magnetic circuits are nonlinear; the reluctance in a magnetic circuit is not constant, as resistance is, but varies depending on the magnetic field. At high magnetic fluxes the ferromagnetic materials used for the cores of magnetic circuits saturate, limiting the magnetic flux, so above this level the reluctance increases rapidly. The reluctance also increases at low fluxes. In addition, ferromagnetic materials suffer from hysteresis so the flux in them depends not just on the instantaneous MMF but also on the history of MMF. After the source of the magnetic flux is turned off, remanent magnetism is left in ferromagnetic circuits, creating a flux with no MMF.

I need to get my mind around the physics in there to work out whether in fact as you claim, increased magnet strength impacts DC resistance (my initial instinct is it does not...)

Also what impact DC resistance has on the signal / the magnetic circuit / generator....

bye for now

David

[neobop]

David,
I'll look over your info when I get a chance.  It's great that you have some time now to explore these matters.

I tried to link to the specifications page for Maestro V2.  If you go back to that link and click on specs, you'll see that output was raised to 4.2mV and impedance is now 700 ohms.  My assertion is based on the assumption that CA changed nothing but magnet strength and increased the wood on the outside.  If you look at the rest of the specs and those of the rest of the line, I think that's a safe bet. 

I don't think gap could be changed, but I really don't know for sure.  I guess AT optimized this years ago and for CA to reduce the gap would require AT  retooling the production line for CA generators?  Makes it seem unlikely in a true moving magnet design.

The difference between DC resistance and impedance might shed some light on this subject.  AT95 has slightly smaller coils than CA - inductance is 400mH as opposed to 420, yet output is the same as V1 and impedance is 2800 ohms.  AT95 doesn't have PCOCC wire - the only difference I'm aware of.
Think it's possible CA doesn't list impedance, only a value within 10% of DC ?  Seeing how they changed the specs from top to bottom on V1 (within normal tolerances), I wouldn't doubt it.  But I really can't make such assertions, I'm at my level of understanding here.  I don't even know how those two carts could have the same output, share the same magnets, and 95 have less inductance.  Maybe they're so close that output is virtually the same. 
neo

[neobop]

I think I've figured out, in a cursory way, some of what's going on with AT spec parameters.

From Phase thread:
"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."

To take that a step further, the greater the inductance, the larger the difference between DC resistance and impedance.  It seems that with AT MMs, the amount of that difference defines an "ultimate" performance parameter.  Favorite old generators had 2.7mV out, 350mH, and approx. 500 ohm resistance and impedance.  When output is boosted either the inductance and/or impedance is increased.  I don't understand how the 150MLX has 350mH and 2.3K impedance, except for it's output - 4mV, as opposed to 2.7mV for the 20SS.  CA increased inductance (420mH) about the maximum that allows both slightly higher output and close values for DC and impedance. 

Why can the V2 Maestro have 4.2mV and 700 ohm impedance and the 150 have 4mV and 2.3Kohm ?  I suggest that there's a maximum output for a given size coil to maintain that desirable relationship between DC and impedance.  For 350mH that output is around 3mV or slightly less.  For 420mH it maxes out around 4.2mV. 
neo

[glrickaby]

Over and above theoretical ideas, is there an inference that the AT150MLX is really the quality equal to the CA Virtuoso/Maestro
and at half the price or less, really a much better buy? What other units would approach this quality level?

[neobop]

Over and above theoretical ideas, is there an inference that the AT150MLX is really the quality equal to the CA Virtuoso/Maestro
and at half the price or less, really a much better buy? What other units would approach this quality level?

Hi GL,
No, not at this level, assuming the CA has a comparable stylus.   That's not to say the 150 isn't an excellent cart, but it's generally agreed (at least by the MM thread fanatics) that the "ultimate" performers are the ones with approx. 500 ohm DC/impedance.  The ones I previously listed, AT-12S, 14S, 15/20SS.  Add to that AT-23 to 25 and some Signet models TK-10ML, TK 9, and TK7LCa?   

Don't expect to buy an old 12S with an aluminum cantilever and a bonded shibata, and get these results, but it should be really nice.  The only round plug stylus with an exotic cantilever still available is the 20SS and it's at least $200.  I recently saw a 15SLa on fleabey and it wasn't all that expensive.  Add around $200 for the stylus and you've got a great cart. 

I don't know of any modern AT that has impedance close to DC figure.  The 150 might be the best in that respect with 2.3Kohm.  The 440 has 3.2Kohm.
In spite of all this the 150 is a venerable performer.  It might require more careful loading.  All ATs need less than 200pF total capacitance load, but the 150 like the 440 might benefit from loading down, especially if shunt capacitance is high.  Usually a value between 32K (440) and 42K will do the job.  But it depends on your system and taste.  LpGear sells the 100E - around $80.  Its generator is identical to the 150 except it has a plastic body and a bonded (.4 x .7 ?) on a straight alum cantilever.  Get a 150 stylus and you have a light weight 150MLX.  Add to that a Vista phono stage for custom loading or get some 400K resistors parallel to net 42K.

I think those old 12E, 13E etc carts with 1200 ohm impedance have good potential, but still the same problem with replacement styli for round plugs.  There's no getting around an exotic cantilever/stylus for top performance.
neo

 

[Grbluen]

Perfect timing Neo, I'm considering the transplant for my LS500. How much work would be required to make the 20SS fit. The LS500 uses the "round plug". Or, what advice would you give to someone attempting to transplant a Beryllium cantilever?

Don

[neobop]

Hi Don GRB,
No transplant required.  The ATN20SS is a round plug.  You might have to trim the plastic, but it's less risky than a transplant.  I expect you'll get nice results like Timeltel and his 13Ea with a 155LC stylus.  The 155LC and 152LC are modern 100 series.  They would require a transplant.
neo

[dlaloum]

I referred to my measurements database....

here are some interesting specs of the relationship between DC Resistance and Inductance in mH
(based on multiple measurements of different exemplars of some of these, assume +/-0.2 due to manufacturing variation)

Grado GF3  10.5 ohm/mH
Grado Gold1 9.2
Technics EPC205mk3 2.9
AT Signet TK10 2.8
Shure V15V  2.6
Shure ML140HE 2.6
Shure 1000e 2.6
Shure V15Vx 2.4
Shure Me75P 2.4
Pickering XSP3003 2.2
Ortofon 530 1.9
AT440MLa 1.6
Ortofon OM 1.6
ADC XLM 1.6
AT Signet MR5 1.4
AT Signet TK6 1.4
AT142LP 1.4
Stanton 500 1.4
AT150ea 1.4
AT14S 1.3
AT13ea 1.2
AT Precept 110 1.1
AT12sa 1.1
AT Signet TK7su 1.1
AT20SLa 1.1
Grace F8 1.0
AT92/95 0.9
Shure M70B 0.9

I should have a V1 CA body in the next few weeks - then I will measure and add it to the database...

I am not seeing a quality trend I this ratio...
I don't have the tools to measure impedance as opposed to DC R.

But thinking about it, impedance is a reactive parameter, as the frequency rises the resistance increases...

this will subtly reduce the high end (possibly balancing out cantilever resonance rise)... so higher impedance = increased reduction in high end (very subtle though!)

What may be of greater relevance is the increased output - if the base generator core construction (pole thickness, laminations, etc..) remains the same, then increased output level (voltage) implies an increased likelihood of saturation.... as the signal approaches saturation, one would expect the high frequencies to get depressed more and more the closer it gets to saturation - so with increased V there would also be a compression of the high end, where the lower level subtle details would  have increased level (due to increased output V) - and the HF peaks would be increased to a lesser degree as saturation of the core starts to kick in.

This would have the serendipitous effect of subtly bringing forward the HF details, without obviously increasing volume (improved soundstage? ) - it is I would suggest, a conscious departure from true neutrality, and also a little underhanded, as it is all done by sleight of hand under the covers, while the main Frequency response still appears linear...

Lots of recording engineers do selective compression of particular frequency bands to subtly highlight certain aspects of a recording (an audiophile no-no!) - are CA doing the same electro-magnetically by upping V out?

A larger (heavier) core, with more laminations would remove this non-linearity, especially if combined with lower strength magnets... (it would also be lower impedance, although DC R is still set by the coils and the wire diameter)
The AT21/22/23/24/25 and TK9/10 are relatively heavy cartridges which also have low inductance and low DC R - these are generally considered to be the all time best MM's made by AT.... DC R is 240ohm (measured), Impedance is 550ohm (spec)

I am still looking at these specs and seeking to understand the interactions/relationships...

bye for now

David

[neobop]

David,
I suspect that it's the relationship between all three, inductance, DC, and impedance that matters.

Isn't impedance calculated?  Resistance at 1KHz combined with inductance and capacitance?  This link has the formulas (same as above): 
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/imped.html

This is just my observation based on AT models/performance.  If the impedance is high, then there's possibly too much inductance for a given resistance.
High impedance tends to sound brighter,  an increase in high end, not reduction.  Example: AT440 - 3200 ohm impedance.  I wonder if phase angle has something to do with this.
Interesting speculation about output and coil saturation.  I don't know if that's a factor but in general, the race for higher output is where the performance level started going downhill.  Except for CA, all the best ATs were < 3mV.  Like Goldfinger II - .9mV, higher output is often perceived as better.  I guess the increased hysteresis distortion/higher output sounds more like digital?   
neo

 

[dlaloum]

Yes but the AT440 sounds bright because of its stylus - not its generator - fit it with a ATN150MLx and it doesn't sound bright....

There are a couple of resonances in the ATN440MLa that tend to make it "bright" - these are not present in the ATN152LP - I sometimes run the 440 body with the ATN152LP stylus - and it is greatly improved .... no longer requires loading down to tame the brightness....

Phase on the other hand may be a factor as phase changes at the resonance points - and there are two resonances with the first being around 13kHz (from memory) and the second around 16kHz - both well within the audible range - and the first influencing/boosting output from as low as 6kHz.

But I agree that high output should be looked on with substantial suspicion - the very best MM's of all brands have tended towards lower output, and sometimes much much lower output (XLZ7500...)

[neobop]

There are so many factors it's hard to know exactly what's doing what.  I have a 440, and with an ATN152ML it was still slightly bright, but nowhere near as with the ATN440ML.  I think cantilever resonances is only part of the story, maybe the greater part. 

Phase anomalies at secondary cantilever resonances seems like uncharted territory.  No doubt something is happening but nothing like 180o phase reversal at primary high frequency resonance. 

Take away 440 cantilever resonance and the generator still isn't a "super" AT.  Either is the 150MLX.  High impedance is indicative of too much inductance for a given generator.  I guess there's no going back (in production) to a lower output cart like a TK10ML or 20SS.  AT should make a generator similar to the CA but with slightly less inductance, more like the AT95 (400mH) but with PCOCC wire.  Put that in a 100 series body and slap a ATN150MLX on, and it should better CA, that is if impedance is low.
neo

[neobop]

For those contemplating a transplant, I think this description might be helpful.
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1200430667&openflup&10200&4#10200

Regards Griffithds: As I've found the reports about the Precept intriguing, a modest amount of research indicates the AT-13Ea at 4.2mV output/1200 ohm output impedance is comparable. An exception is the 13Ea's metal mounting shroud rather than the Precept's plastic.

Purchased a 13Ea with a broken cantilever, mounted on a low mass AT waffle-pierced style headshell. An ATN-155LC cantilever transplanted to the original AT-13Ea grip results in the appropriate VTA/SRA, self-resonance of the cartridge is minimal.

Exceptionally solid center image, pleasing layering, depth & channel balance. Soundstage is in front of the speakers. Depth develops from well forward to a front center stage, an unusually lively hall effect ambience results, speaker location is removed as a source of distraction. Piano strings resonate & background vocals/subtle nuance emerge. Response is smoothly developed, there are no noticeable peaks.

Bass notes retain individual identity, presented with conviction. Speed in rise time and decay is gratifying. Midrange/hf grain is minimal.

Don, in attempting the cantilever exchange begin by removing as much of the compliance screw sealant as possible. Be sure to use a correctly sized screwdriver and use it to clear sealant from the screw slot, Turn the screw slightly & reverse repeatedly until the screw travels the necessary amount. One to one & one-half turns should release the cantilever. Pushing from the back with a pin rather than trying to pull it out is recommended.

Insert the cantilever and with the compliance screw turned upwards, view and align the V-magnets from the rear to confirm azimuth relative to a horizontal surface of the grip. Holding the grip between thumb and middle finger, apply pressure with fore-finger directly in line with the cantilever axis. Double check azimuth and tighten the compliance screw. This may require more pressure than anticipated on the first effort. Too little will result in the magnets contacting the poles when VTF is applied. It may be best on the initial trial to apply a small amount of pressure, test and then gradually increase until distortion at the desired VTF is eliminated.

Initial concerns are that VTA/SRA are correct, confirming azimuth after tightening the compliance screw is obviously important. I can't speak for the Precept but the 13Ea Frankencart impressed me enough (especially soundstage) that the initial example was sent to Halcro for confirmation, Henry wrote that he was pleased with the cart. Good luck &
Peace,


The 155 is of the 100 series (modern), going into a round plug 13Ea.  I don't know if anyone successfully transplanted an exotic 100 series into a 3400 series (CA) plug. 

Don Griff,
You said you're sending one to Soundsmith.  Did you attempt an exotic transplant into a CA plug? 

neo

[neobop]

From the same thread as the previous post, here's something about cantilevers from J Carr:

From the perspective of a cartridge designer, the most commonly used figure-of-merit for a given material is propagation velocity - how rapidly it transmits sound. And this is determined by the material's specific gravity (lower is better), and Young's modulus (higher is better).

With this target in mind, the best material is diamond. Although its specific gravity is a bit high at 3.52, it is so stiff that its 16,770m/s propagation velocity is the greatest among known materials.

Second best is boron. Its 2.3 specific gravity is lower than aluminum, and it is quite stiff as well, giving a propagation velocity of 13,500m/s.

Third is beryllium. Although a specific gravity of 1.8 makes it the lightest among typical cantilever materials, it is also considerably less stiff than boron, which brings its propagation velocity to 12,300m/s.

Fourth is ruby / sapphire. Its 4.0 specific gravity is high, but it is saved by having a Young's modulus which is higher than beryllium but poorer than boron. Its propagation velocity drops down to 9400m/s.

5th is aluminum. A 2.7 specific gravity is reasonably low, but its Young's modulus is also low, resulting in a propagation velocity of 5200m/s.

6th is titanium. Specific gravity of 4.5 is very high, and Young's modulus is not so high, which in concert reduce the propagation velocity to 5160m/s.

However, the last two materials are ductile and not brittle, which means that the joint between stylus and cantilever is less reliant on glue. Any glue that I am aware of has a slower propagation velocity than even hardened aluminum, so to be able to have a thinner layer of glue between the stylus and cantilever, or no layer, is a distinct advantage which partially counteracts the other limitations of aluminum and titanium.

Also, I am reasonably sure that beryllium production in Japan has either stopped or at best is much smaller than it was in the 1970s and 80s. Since beryllium is poisonous and producing it results in environmentally hazardous wastes; regulations have become more strict, and public opposition more vocal. Various cartridge designers including myself have avoided beryllium because of the environmetal impact.
neo

[dlaloum]

As I recall, that posting led to various people asking for retips with the needle press mounted in Aluminium - with very positive results...

What JCarr did not discuss in that posting, was the impact of shape and mass - that is to say, in tube form, there is increased rigidity, and decreased mass - so aluminium in tube form gets a leg up the scale vs others in rod form.


Furthermore if it is tapered tube then there is a further improvement.

In the 80's there were diamond and sapphire tubes as well as boron and berillium tubes...

Now everything except aluminium is in rod form.

Audio Technica never used exotic tubes, their TOTL were always exotic rods, and the next notch down tapered aluminium.

The speed of propagation in the material vs rigidity (reduction in flex = reduction in distortion) vs effective mass - with little or no idea of which has the greatest impact on sound and in what way...

[neobop]

Actually, this is a more recent post from J Carr - a few weeks ago. 

I think I like beryllium with AT carts, maybe because it's the lightest.

neo

[griffithds]

Neo,


"Don Griff,
You said you're sending one to Soundsmith.  Did you attempt an exotic transplant into a CA plug?" 

I have installed the AT 150MLX stylus and find it not as big an improvement as I though I would when it is compared with the AT 440MLa stylus.  There are things about each of them that is better than the other.  The MLa has a more relaxed presentation where as the MLX  has a presentation that is  more in your face. I think the better buy for transplanting into this CA is the MLa stylus. When the MLa is in the Virtuoso, it sounds like the MLX in the Maestro. The MLX in the Virtuoso sounds a little bright. I am beginning to think that the extra wood that is on the Maestro sort of over damps what is being presented to it by the stylus.
I haven't got around to sending anything off to SS yet.  Other priorities at the moment. New TT and arm. (New to me)
Regards,
Don

[neobop]

Neo,


"Don Griff,
You said you're sending one to Soundsmith.  Did you attempt an exotic transplant into a CA plug?" 

I have installed the AT 150MLX stylus and find it not as big an improvement as I though I would when it is compared with the AT 440MLa stylus.  There are things about each of them that is better than the other.  The MLa has a more relaxed presentation where as the MLX  has a presentation that is  more in your face. I think the better buy for transplanting into this CA is the MLa stylus. When the MLa is in the Virtuoso, it sounds like the MLX in the Maestro. The MLX in the Virtuoso sounds a little bright. I am beginning to think that the extra wood that is on the Maestro sort of over damps what is being presented to it by the stylus.
I haven't got around to sending anything off to SS yet.  Other priorities at the moment. New TT and arm. (New to me)
Regards,
Don

Thanks Don,
This is very interesting.  Over-damped is how Raul described the sound of Maestro (V1) compared to Virtuoso, although he wound up with boron/micro on the Virtuoso.  The thing about beryllium is that it's more flexible than boron, but more controlled than aluminum. With it's low mass it would have the best transient response (?), and apparently the near perfect comprise between warmth and resolution.  Too bad beryllium/ML is now virtually unobtainium.

Now all the top CA V2 have more extensive wood like V1 Maestro.  I wonder if this damping is more compatible with the higher output.  I suspect David is right about higher output and the possibility of compression causing some to perceive "formerly hidden detail". 

Well, you've once again broken new ground Darth Griff.  You've successfully transplanted an exotic cantilevered stylus into a 3400 plug, from a 100 series.
This is the transplant where both David and I broke beryllium cantilevers.  You get the Captain Quirk Award for going where no man has gone before!!

Kudos for Darth Griff.          

neo

[dlaloum]

Whereas I am permanently scarred by the experience - snapping an intact beryllium cantilever in half 

[griffithds]

Dlaloum, Neobop,

I went very slowly and did not  in anyway, try  to change the angle of the cantilever.  I remembering Timeltel mentioning the same thing when he did his AT13Ea Frankenstein. Just making adjustments in VTA using arm height.   I'm beginning to think that the cantilever material is just a very small part of the overall design.  I have always thought beryllium or borron cantilevered cartridges were the best, but I am now beginning to understand that perhaps it's not just the material, but how it is executed in the design. A short, thin, tapered aluminum cantilever with a quality ML tip, can be better than either a beryllium or boron cantilever. Perhaps it's the care and execution of the design that matters most.
Just my 2 cents!

Best regards to both of you,
Don

[dlaloum]

Always comes down to "all things being equal"....

Tapered beryllium foil.would.be.nice....

Just realised this evening that I can fit my Shure m97xe SAS to my grave f8 body.... R= 550 Z=500, I also have Shure bodies where z=500 but r=1550..... An interesting comparison.... Measurements should be identical, but how will the s pound differ?