[Grbluen]

John,
I appreciate your review.  I have a request.  If it's possible,  could you expand your list of reference recordings.  I'd like to be able to compare notes,  but I don't have any of the records listed.  Part of the trouble with a solitary hobby such as this,  is that I'm not always sure of what I should/could be hearing.

Don (grb)

[jschwenker]

John,
I appreciate your review.  I have a request.  If it's possible,  could you expand your list of reference recordings.  I'd like to be able to compare notes,  but I don't have any of the records listed.  Part of the trouble with a solitary hobby such as this,  is that I'm not always sure of what I should/could be hearing.

Don (grb)

Hi Don,
"Audio Reference Recordings" - good idea for a sticky topic, seems to me.  I'll throw out a few more here.  A lot of times I get too distracted by good music, so maybe some of these will simply be exemplary recordings that also happen to have great musical stuff going on.

Harry James, the Sheffield direct to disks:  "The King James Version"  "Still Harry After All These Years"  "Comin' From a Good Place".  To me, the first of these never sounded quite as spectacular as the other two, where they got it just right - great miking of all, good beefy big band sound, amazing full throated brass.  (probably pretty good on CD transfer as well)

Rob Wasserman, "Duets"  (LP & CD)  Very well recorded all around, no surprise particularly on Mr. W's bass work.  Duet with Jennifer Warnes particularly notable for the depth and complexity of image.  Cheryl Bentyne's "Angel Eyes" is remarkable for her powerful delivery of this classic - give yer midrange a stiff workout.

Christian Mcbride,  "Gettin To It"  (I have CD only)  Some very amazing acoustic bass work.  "Splanky" with Ray Brown and Milt Hinton forming a bass only trio and "Night Train" as a solo.

Linda Ronstadt,  "Simple Dreams"  (CD & recent audiophile LP release)  About as sumptuously hung together of a pop album of the time as one is likely to come across.  She was somewhere near the peak of her career and had a backing band of among the best to match.

Tom Waits, a few albums from early-ish in his career:  "Small Change"  "Foreign Affairs"  "Blue Valentine".  (CDs, LPs and some have been out as various high grade LP re-issues)  They were painstaking recorded by the Wally Heider outfit, Bones Howe production, with a pretty consistent crew of great session performers.  (Shelly Manne, Jack Sheldon, Frank Vicari)  Gorgeous overall sound.  (As much as I love what he and wife/work partner to be Kathleen Brennan pulled off in the soundtrack of "One From The Heart"*, I really prefer the pre Ms. Brennan portion of his career)  *highly recommended too...

"Dr John Plays Mac Rebennack"  (LP & CD)  Pure piano joy from one of the best - and a stellar purist piano recording from Crystal Clear Records, if I'm remembering right.

Stravinsky: The Firebird/Borodin: Music from Prince Igor  (Telarc LP & CD)  A very spirited Firebird, an exemplary orchestral full bloom sound.  Polovetsian Dances also very remarkable.  As somewhat similar through Telarcs, the capture of the bass drums lies somewhere devilishly between heavenly and ever so slightly overcooked.

Repercussion Unit,  "In Need Again"  (CMP LP & CD)  Well done group miking of the rather complex instrumentation brought to the table.  Lots of fun as well as a real workout for challenging the time coherence of a system.  They do use some drum machine programming but it is pretty palatable, even for one not very much favoring such...

"Drumline",  Soundtrack.  (CD only, probably)  A very watchable movie, with a mostly rather forgettable collection of pop/rap songs.  EXCEPT, tracks 1 and especially 16** - there you have the purest expression in audio I have run across of sitting 10 feet away from a well drilled marching band percussion outfit.  Muy Explosivo!!  (**For some reason it appears that some disks floating around leave off track 16 - don't buy one of them)

John Hartford, Pat Burton, Benny Martin,  "Slumberin' on the Cumberland"  and  John Hartford,  "Morning Bugle".  (LP & CD)  Mr. Hartford, always way devoted to the music of his life, was also pretty devoted to associating with folks that could get the audio just right.  (Morning Bugle is recorded as a trio gathered around one pair of mikes)  Both albums are tons of fun and filled with gorgeous sounds.

So there's a hit or miss little collection for youze.  When record store folks ask what sort of music I like, I tend to say "I'm unreliable" - there's few things I don't like at least a little...

Cheers,  John

[Grbluen]

Thanks John!  That's a pretty decent list to accompany me to the record store.  I'm actually stunned that I don't have a single recording from your list.

[plastico]

I did this mod to my RB300, and it gave me excellent results. I have done this mod with lead fishing weights on my RB300 arm. Each weight is identical at 11.5 grams, I just made them the same weight. I slightly drilled them out to fit snuggly on the stainless acorn nuts. I then painted them black and superglued them on the nuts. I found this to be very beneficial. It increased the silence and the sound stage as well. It also gave me great tracking, although I had to decrease the anti-skate.

Cheers, Plastico

[roscoeiii]

I did this mod to my RB300, and it gave me excellent results. I have done this mod with lead fishing weights on my RB300 arm. Each weight is identical at 11.5 grams, I just made them the same weight. I slightly drilled them out to fit snuggly on the stainless acorn nuts. I then painted them black and superglued them on the nuts. I found this to be very beneficial. It increased the silence and the sound stage as well. It also gave me great tracking, although I had to decrease the anti-skate.

Cheers, Plastico

Love those Audiomods arms. Curious about how your modded RB300 compared to the Audiomods in the bass?

[neobop]

I did this mod to my RB300, and it gave me excellent results. I have done this mod with lead fishing weights on my RB300 arm. Each weight is identical at 11.5 grams, I just made them the same weight. I slightly drilled them out to fit snuggly on the stainless acorn nuts. I then painted them black and superglued them on the nuts. I found this to be very beneficial. It increased the silence and the sound stage as well. It also gave me great tracking, although I had to decrease the anti-skate.

Cheers, Plastico

That's encouraging.  It's certainly a far cry from John's 200g/side SME mod.  Maybe the effectiveness is increased by cart compliance.  What are you using?

Is that a VTAF? 
neo

[plastico]

I was using a Denon 301 mk2 on the arm, neo. Before that I used a SAE 1000e. And yes, that is a VTAF- it was worth every penny! The RB 300 arm with the mod was very prestigious in the bass, roscoeiii, but it did not give me the refinement that the AM arm gives me. I could have lived very happy with my modded RB300, but then I caught the sickness! 

Cheers, Plastico

[jschwenker]

I did this mod to my RB300, and it gave me excellent results. I have done this mod with lead fishing weights on my RB300 arm. Each weight is identical at 11.5 grams, I just made them the same weight. I slightly drilled them out to fit snuggly on the stainless acorn nuts. I then painted them black and superglued them on the nuts. I found this to be very beneficial. It increased the silence and the sound stage as well. It also gave me great tracking, although I had to decrease the anti-skate.

Cheers, Plastico

Nice! - and simple...  Glad you got good results.  Still not sure I'm seeing a direct reason for such a mod to change the anti-skate force requirement.  Can you tell me things I might not know about this arm's design and anti-skate method of application that might enlighten me?  Thanks.

It's certainly a far cry from John's 200g/side SME mod. 

neo

Yo, easy there - my mods added ONLY 100g/side, 200g total. 

Cheers,  John

[plastico]

I am not sure as well. I had the anti-skate set at 1.5, and after the mod I found the setting to be .75. I know the Rega anti-skate is very strong to begin with, perhaps the extra weight helped to calm that down. I do know that before the outriggers, even with the anti-skate set to 0, the arm would still want to come toward the platter. With the mod I got no arm travel with it set at 0. Maybe someone with a better understanding of the mechanics could chime in here.

Cheers, Plastico

[jschwenker]

Thanks for the response plastico.  For all of my gabbing about method and engineering - sure they'll lead much of the time to sensible answers but not always.  Any number of times I've had to say "well that's just what the hardware did, whether we can explain it or not"  (occasionally being directed by my bosses to spend a lot more time & money to run down a better idea of why - and also occasionally, coming up with an actual better answer, haw, haw...) 

Here I experimented with the anti-skate after my mods - using the 1000 Hz increasing modulation test on Telarc's Omnidisc.  (other disks also have similar things)  I was finding a setting that was less than 0.1g greater than numbers I had written down from the last time I did the test, pre mods.  I left it at the new setting but can't be too sure that the difference was anything of real significance.  (if I did the test 5 times I'd probably get spread in the data greater than that 0.1g)

Yers,  John

[plastico]

Love your reply John. I try to wrap my head around the "this is why it works" explanations, but sometimes it gets too heady, and my eyes start to glaze over! I first seen this in a Audiogon forum and decided to give it a try. Hey, it was totally reversable, so I researched and noticed that a couple of other makes of arms implimented the same KIND of idea.

Cheers, Doug

[dlaloum]

Hmm thinking laterally....

On the Revox with its arm which is all of 2" long - about the size of a headshell - it would be difficult to fit lateral mass off the pivot, but it might be possible to fit a back end longhorn onto a cartridge body...

Would it make sense fitting a longhorn mod to the BACK (rather than the front) of a Grado cartridge?

On the Revox that would place it quite close to the pivot (no I have not taken any measurements - just tossing up the idea to get some thought feedback on it)

bye for now

David

[neobop]

David,
Would it be possible to post a photo of the arm with the cover off ?   I know there's not a lot of extra room in there, but maybe you could implement something with a moderate weight using distance from the lateral plane to increase eff mass.  Sort of like John's SME, only less weight.

Perhaps, if you increase lateral mass more than vertical, you could get the desired affect with the outrigger?  I guess you'd have to take the tracking mechanism into account.
neo

[neobop]

I've been thinking about the idea of adding mass someplace other than the plane of the lateral pivots.  Not sure how the physics works. 
Mass added down the arm somewhere will add to vertical mass (at least to some extent), but could be counterproductive laterally on a pivoting arm.  The arm tube is usually set at an angle that's not 90o from the plane of the lateral pivots so you'd possibly be setting mass at, or creating another force vector.

A longhorn is on the cart and whether the front or back, is perpendicular to the groove.  This should stabilize the cart, but I don't know how it will affect lateral mass on any type arm.  I suspect most if not all of the affect will be vertical. 
neo

[neobop]

I've been thinking about the idea of adding mass someplace other than the plane of the lateral pivots.  Not sure how the physics works. 
Mass added down the arm somewhere will add to vertical mass (at least to some extent), but could be counterproductive laterally on a pivoting arm.  The arm tube is usually set at an angle that's not 90o from the plane of the lateral pivots so you'd possibly be setting mass at, or creating another force vector.

A longhorn is on the cart and whether the front or back, is perpendicular to the groove.  This should stabilize the cart, but I don't know how it will affect lateral mass on any type arm.  I suspect most if not all of the affect will be vertical. 
neo

Not getting a lot of help here.....  As LBJ used to say, "Come, let us reason together." 

When I said counterproductive laterally, I meant for the goal of increasing lateral eff mass or increasing it more than vertical mass.   An outrigger on the cart is pretty much the same as increasing the weight of the cart (as far as mass goes).  On a linear arm this will increase vertical eff mass and probably do nothing for lateral mass.

I think horizontal mass on a linear arm is defined by the mass of the moving mechanism?  That's where the mass must be added methinks, and some experimentation is probably required to see how much weight can be added in the space, and how much before you screw up the linear tracking function.
neo

[jschwenker]

Hi David, Neo,

Was out of touch with the circle for a few days.  Yes, would be interested in seeing a picture of the Revox as well...

Pretty much, any mass* added anywhere toward the cart end of a pivoted arm will act to influence both vertical and horizontal effective mass.  (* small masses like Mapleshade and others have made, and the longhorn)  They may succeed in bringing an arm/cart natural frequency into the desired zone if the cart was too low in compliance for the particular arm mass.  In the case of the longhorn, if the arm is relatively torsionally weak about the armtube axis it could help stabilize that, though seems to me that that may happen in a somewhat higher frequency region.

Yes, any mass added anywhere on a linear tracker will add directly gram for gram to the lateral eff mass.  (might help to think of linears as pivoted arms with the horizontal direction pivot as being infinitely far away, therefore any mass added is as if AT the cart end of the arm)  If it was added to the linear motion assembly only then it would only affect lateral eff mass.  Mass added to the vertically pivoted arm would add lateral eff mass AND in a ratio to its location along the arm to the cart, would add to the vert eff mass. 

Per previous calculations I'm betting it would take a lot of mass to adversely affect lateral tracking function - based purely on mass/inertia.  However, adding mass to some linear trackers could also significantly increase the friction in the bearing system, leading to increased tracking problems.

My 2x10 to the minus 8 mega-bux worth...

Cheers,  John

[jschwenker]

The SMErch arm - Natural frequency measurements

Hi Folks,

The executive summary is that the mods previously described have resulted in measured behaviors pretty consistent with those predicted by the math.




Fig. 1 - Test tools/conditions.  During readings turntable was running, with stylus in last (locked) groove of record side - placing cart cantilever in a fairly normal frictional drag condition.  The applicator stick was used to very lightly strike the indicated surfaces.  An oscilloscope was connected as described below to preamp outputs.




Fig. 2 - Vertical direction impulse response.  Scope was connected to one channel output only.  My best current recording capability is to take movies of the scope screen with a digital camera and select frames.  Scope setting was 50 mS/div - however - rather than fine tuning it there, trusting the modern camera's 15 frames/sec, I found it was actually closer to 58 mS/div.  At about 1.9 div/cycle the vert fn = 9.0 Hz.




Fig. 3 - Horizontal direction impulse response.  Scope was connected to both channels output, with same polarity.  (for mono signal)  At about 3.9 div/cycle the horiz fn = 4.4 Hz.  This fig is with the SME horiz damper engaged to about max level with the fluid.  Clearly the impulse is being damped out at a generally greater rate than in Fig. 2 but is also clearly less than critically damped, given multiple cycle settling time.




Fig. 4 - Horizontal direction impulse response WITHOUT damping.  Same setup as Fig. 3 but with horiz damper screw removed from fluid.  Again at about 3.9 div/cycle the horiz fn = 4.4 Hz.  Clearly the relative impulse amplitude is not falling out quite as fast as in Fig. 3 but the natural frequency is not detectably different.  (not unusual for damping ratios in the well underdamped region)


The natural frequencies in the two directions are at just about the ratio predicted by the math work done prior to the build.  (my 22 Jan 2014 posting has the original prediction calculations of 7.5 and 3.7 Hz respectively)  Both measured values here are approximately 20 percent higher than was predicted.  I explored several possibilities for the disagreement: 
1)  First was that the cart compliance could be speced purely in cantilever motion at 90 deg to the shaft, rather than some 20 deg off of that as the shaft is positioned with respect to the record surface.  This does work in the right direction but makes only for a 3 percent difference at best.
2)  With my particular cart, I am using the arm toward the low end of the mass range of carts it can carry.  The arm effective mass will vary somewhat non-linearly with the counterweight position.  Again this effect would move things in the right direction but would result in only a few percent error in calculated fn.
3)  I am left to conclude that the compliance of this cart/particular cantilever is likely somewhat off spec.

I MAY work to bring the fn back toward the 8 Hz or so area that I think may be ideal, by adding a little mass to the headshell.

The best news here is that it is possible to predict with reasonable certainty the effect of added lateral effective mass.  Due to the natural frequency going by the square root of delta effective mass, it can be seen that it takes a fairly large change in mass to introduce a more modest change in fn.  Here I have increased the lateral effective mass by approximately 4x and indeed seen a reduction in horiz fn of approx 2x.

Cheers,  John

[jschwenker]

Yes, any mass added anywhere on a linear tracker will add directly gram for gram to the lateral eff mass.  (might help to think of linears as pivoted arms with the horizontal direction pivot as being infinitely far away, therefore any mass added is as if AT the cart end of the arm)  If it was added to the linear motion assembly only then it would only affect lateral eff mass.  Mass added to the vertically pivoted arm would add lateral eff mass AND in a ratio to its location along the arm to the cart, would add to the vert eff mass. 

Per previous calculations I'm betting it would take a lot of mass to adversely affect lateral tracking function - based purely on mass/inertia.  However, adding mass to some linear trackers could also significantly increase the friction in the bearing system, leading to increased tracking problems.

My 2x10 to the minus 8 mega-bux worth...

Cheers,  John

Hi Folks,

A weakness in my above statements on linear trackers:  I failed to distinguish between two significant classes...
1)  Free floating or self tracking - are arms that ride on light friction linear bearings, such as air bearing slides or precision rollers on nice guideways - such that side forces on the stylus are what drives the linear motion.  (A few manufacturers with product in this area:  Clearaudio, Eminent, Walker, Magne)
2)  Active or servo driven - designs that are driven linearly by a mechanism of some type that keeps the arm pivot (for both vertical and horizontal) moving in a linear fashion to about exactly follow the cart's progress across the record radial line.  (A few manufacturers with product in this area:  Bang & Olufsen, Revox, Sony, Technics)

My remarks quoted were entirely addressed to class 1) above.  Based on the designs I've seen, it might be quite difficult to impossible to add lateral effective mass only to designs in class 2).
Sorry about the missing detail there. 

Yers,  John

[neobop]

Hi Folks,

A weakness in my above statements on linear trackers:  I failed to distinguish between two significant classes...
1)  Free floating or self tracking - are arms that ride on light friction linear bearings, such as air bearing slides or precision rollers on nice guideways - such that side forces on the stylus are what drives the linear motion.  (A few manufacturers with product in this area:  Clearaudio, Eminent, Walker, Magne)
2)  Active or servo driven - designs that are driven linearly by a mechanism of some type that keeps the arm pivot (for both vertical and horizontal) moving in a linear fashion to about exactly follow the cart's progress across the record radial line.  (A few manufacturers with product in this area:  Bang & Olufsen, Revox, Sony, Technics)

My remarks quoted were entirely addressed to class 1) above.  Based on the designs I've seen, it might be quite difficult to impossible to add lateral effective mass only to designs in class 2).
Sorry about the missing detail there. 

Yers,  John

David,
I thought as much concerning your Revox.  It seems like air bearing linear arms have a big advantage as far as adjustable mass.  The horizontal mass is already high in comparison.  ET and Trans-Fi are 60 to 80g eff horiz mass.  It can be increased by adding weight to the sled, but I don't know all the considerations with air pressure, etc. 

Maybe if you switched from disposable diapers for the baby, to old fashioned wash-em ones, it could finance a Trans-Fi?  Maybe the sound of the pump would lull the baby to sleep and you could listen on headphones.  Sorry, couldn't restrain myself.  How is everybody doing BTW?
neo

[jschwenker]

Hi Neo, David, Roscoeiii, etc.

You folks (and maybe others looking in) seem like you probably have about as good a view as to the layout of most all things Vinyl Circle.  I'm wondering if you could point me to any old threads where it might make sense to add some detailed descriptions of a couple of other DIY adaptations folks may be interested in looking at.  Specifically, I have:

A)  1 Hz turntable isolation stage.  It is built onto a typical TT wall mount shelf already providing reasonable floor isolation in the vertical direction.  It then effectively floats the TT platform on 9 inch pendulum links giving good isolation from wall in/out movements due to subwoofer LF pressure waves in the room.  No doubt not for everybody but it was fairly straightforward to build and it seems like the kind of situation I had would not be too uncommon.  (that of wanting some of both floor and wall isolation in an otherwise ordinary house sort of structure)
B)  Platter mods to accept a ring clamp.  Specifically I modified an old VPI platter to allow it to work with the VPI ring clamp - that these days mates up to slightly larger diameter platters in newer VPIs.  The general approach could be applicable to any number of other platters/TTs/clamps.

Thanks for any suggestions.

All the best! 
John