[Gzerro]

I was trying out some damping fluid on my JMW Classic arm and I noticed that the spike on the Unipivot base didn't seem as sharp. I'm gussing that this is a problem, but it may look worse magnified. Here are some pics from my cheapo USB Microscope:

I've tried to be gentle with the arm, but maybe I bumped the spike at some point. I'm guessing this may be the cause of the sibilance I can't get rid of. The pics are from behind the arm base, so it's bent toward the platter.
 
I've contacted VPI to see if they can help.

Good find.

Way beyond my paygrade to know what difference it would make, but I look forward to hearing what VPI has to say.

[robbiesurp]

VPI has asked me to return the part. I'm not sure if they repair the spike or replace it. Hopefully I'll know more about the cost of the repair next week. I was hoping this part would be user replaceable but I guess it's more involved...

Hey Tom,
Is the spike on your arm damaged at all? I'm still curious if this could be the source of the problem.

[jimdgoulding]

I have given this problem quite a bit of thought. So far, I think it's actually like 3 problems in one. The first is the lack of correct anti-skating. The stylus is riding the rail on the inner groove and slightly "stone skipping" on the outer groove. Unfortunately, the upper tenor/soprano area also seems to be a resonance frequency harmonic of the arm/cart combo, but that is maybe a guess. The third problem may be from azimuth "roll". But for this to happen, I have to ask if it seems to occur at a warped area of the record?

One of the problems with uni-pivots is the rolling of the azimuth while in play. The cartridge will bob back and forth (to the record terrain) and loose firm contact with the record groove, and since the anti-skate is lacking, that groove is the outer groove (right channel).

Soundsmith does have a cartridge that is made for the uni-pivoted VPI arm. Unfortunately it's about $1K.

Wayner

[neobop]

I was trying out some damping fluid on my JMW Classic arm and I noticed that the spike on the Unipivot base didn't seem as sharp. I'm gussing that this is a problem, but it may look worse magnified. Here are some pics from my cheapo USB Microscope:






I've tried to be gentle with the arm, but maybe I bumped the spike at some point. I'm guessing this may be the cause of the sibilance I can't get rid of. The pics are from behind the arm base, so it's bent toward the platter.
 
I've contacted VPI to see if they can help.

This spike is inverted - mounted on the base and point facing up?

What is the height of the contact point relative to the arm tube and the plane of the record?

Stainless steel spike?

How is pivot damping implemented on the 10.5, at the base of the spike?

neo

[robbiesurp]

"This spike is inverted - mounted on the base and point facing up?"
Yes it points up and the arm balances on it.

"What is the height of the contact point relative to the arm tube and the plane of the record?"
I'm not sure, but it looks to about on the same plane.

"Stainless steel spike?"
I believe that it is Tungston Carbide

"How is pivot damping implemented on the 10.5, at the base of the spike?"
The damping fluid goes in the trough at the bottom of the spike. The bottom edge of the armwand makes contact with the fluid in the trough when it is placed on the pivot point.

[neobop]

"This spike is inverted - mounted on the base and point facing up?"
Yes it points up and the arm balances on it.

"What is the height of the contact point relative to the arm tube and the plane of the record?"
I'm not sure, but it looks to about on the same plane.

"Stainless steel spike?"
I believe that it is Tungston Carbide

"How is pivot damping implemented on the 10.5, at the base of the spike?"
The damping fluid goes in the trough at the bottom of the spike. The bottom edge of the armwand makes contact with the fluid in the trough when it is placed on the pivot point.

Hard to believe. 
Wayner's unipivot objections certainly apply.  In order to maintain lateral stability a unipivot must have a vertically offset pivot, at or near the plane of the record.  That prevents or minimizes rocking, azimuth changing or roll, and maintains lateral tracking (bass) stability.

I don't know who designed the arms or why Harry adopted them, but I wonder how much greater the Classic would be with a better arm. 




This is the Sonus Formula 4, designed by Peter Pritchard.  The spike faces down and goes into the bottom of the steel well near the plane of the record.  You can see how the arm tube is vertically offset.
It's ironic, now they can use that plastic 3D imaging on an ill-conceived design.
neo 
 

[robbiesurp]

Hey Neo,

Please take my estimation of the pivot point with a grain of salt. I haven't measured it and my pivot point is on it's way back to VPI. Maybe someone else can take a look at theirs and report back.

[Wayner]

I think that if VPI wants the arm to be more of a success, (and wondering why the Traveler has a gimball arm) they need to fix this problem. Maybe with magnetics at the base (and maybe a magnetic anti-skate would also be needed) to stabilize the arm.

This is the number one reason I have not put some cash down on any new VPI. I love the mass of the plinth and platter/motor, but I don't like the arm, for the reasons here in this thread.

Wayner

[Devil Doc]

Fiddle-dee-dee. Here I was saving my pennies for a Classic; Now I'm not so sure.

Doc

[Wayner]

It's still a hell of a deck, just gots some things to work out.

BTW, my favorite table right now is my VPI-HW19jr. with the AudioQuest PT-6 arm. I don't know what more I would want. It's quiet, the arm functions perfectly, anti-skate works flawlessly (IMO) and during listening sessions, one simply forgets about listening to a turntable, just the music.

There just isn't a "prefect" turntable out there in my opinion. Many come very close, but there is always some little thing that gets in the way. I'd certainly enjoy working on the uni-pivot arm to see what I could tinker up. I like doin' stuff like that. Maybe it shouldn't be a point, but rather a knife blade that the arm pivots on, but then it would need to have a bearing for the sweeping arm.

Wayner

[Devil Doc]

Ironically, that's my set up as well, except my cartridge is a Sumiko Blue point 2. I've had it nearly 20 yrs. and I really don't have any complaints, other than an itch to change.

Doc

[Gzerro]

Hey Tom,
Is the spike on your arm damaged at all? I'm still curious if this could be the source of the problem.

I checked out the spike on my arm and with 10x magnification it looks straight and the point is not flattened like yours.

Reading the various posts here - along with several similar unresolved threads elsewhere - I am about ready to just give up and get another table.

I bought the Scout used on a whim for a great price, and it has been good enough to revive my interest in vinyl. That alone has been worth the price of admission and I am really glad I purchased it.  Maybe it is time to move on instead of investing more time, frustration, and money on the Scout trying to fix this issue. Even though the problem may be self inflicted due to the setup being off somewhere, it just shouldn't be this hard.

[Gzerro]

Please take my estimation of the pivot point with a grain of salt. I haven't measured it and my pivot point is on it's way back to VPI. Maybe someone else can take a look at theirs and report back.

On the JMW-9 the top of the spike at the pivot point is about 3/4" above the plane of the record, so there is some vertical separation.

Also, as a last effort I tried Lofgren B alignment. It was no different in terms of the sibilance distortion, maybe a bit worse.

I look forward to hearing back from you after VPI looks at your arm.

[robbiesurp]

I checked out the spike on my arm and with 10x magnification it looks straight and the point is not flattened like yours.

Reading the various posts here - along with several similar unresolved threads elsewhere - I am about ready to just give up and get another table.

I bought the Scout used on a whim for a great price, and it has been good enough to revive my interest in vinyl. That alone has been worth the price of admission and I am really glad I purchased it.  Maybe it is time to move on instead of investing more time, frustration, and money on the Scout trying to fix this issue. Even though the problem may be self inflicted due to the setup being off somewhere, it just shouldn't be this hard.

I hear you. I had a Rega Planar 25 before the classic and although the Classic sounds much better I sometimes miss the simplicity of the more "nonadjustable" Rega. I moved to the Classic because I was having some isolation issues with the Rega when i moved to a home with suspended wood floors. I guess it's all part of this hobby, as soon as I solve one problem I notice something else...

Hopefully this thread will end with some solution. I'm curious if a new pivot spike will make the difference. According to VPI, it's extremely hard to damage these spikes barring a serious jarring incident like dropping the table. I bought the table new and I've never moved it from the top of my rack since I got it, so the whole thing seems puzzling.

[Wayner]

Put a Rega RB303 arm on the VPI. That would be a hell of a deck, IMO.

ner

[neobop]

I had a Rega Planar 25 before the classic and although the Classic sounds much better I sometimes miss the simplicity of the more "nonadjustable" Rega.

The Classic sounds much better, I wonder why?

I took a quick look for information about these arms and ran across a Fremer review on the Classic 3.  I got to the part where he was referring to the improvements in the arm and how the JMW Classic center of gravity was admirably low, then quit.  You might find this paragraph of interest:

"Since its launch, the JMW Memorial arm has undergone significant renovations that have resulted in major mechanical and sonic improvements. While the JMW-Classic retains the concept of the original, almost everything about it has been rethought and upgraded. On the original arm, azimuth was set by rotating an offset ring attached by an O-ring to the lower part of the arm's bearing-cup housing. Thus the O-ring, attached to a high mass, essentially acted as an unwelcome high-frequency spring vibrating at musical frequencies. On the JMW-Classic the azimuth is set by rotating either that ring or the counterweight. The original cantilevered bearing platform was relatively thin and unsupported. It is now far more massive and rigid, and a secondary locking support ensures rigidity. The circular mounting block of stainless steel makes possible the rigid connection of arm to plinth, and the overall design ensures a commendably low center of gravity"

http://www.stereophile.com/content/vpi-classic-3-turntable-amp-classic-jmw-tonearm

Perhaps the O ring can be damped externally once azimuth is set?  You could probably do it with one tiny damping dot, that is if you still have the problem.
I don't know if this will cure the JMW 9, but it's worth a try.
neo

[Gzerro]

Perhaps the O ring can be damped externally once azimuth is set?  You could probably do it with one tiny damping dot, that is if you still have the problem.
I don't know if this will cure the JMW 9, but it's worth a try.
neo

Again thank you for your continued feedback.

I have never used that adjustment, the counterweight which also sets azimuth is more straightforward to use with the SoundSmith Counterintuitive for fine adjustment. Damping various parts of the arm would be something to try, and wouldn't cost much.

Would herbie's thin grungebuster dots work, or is there something better to try?

Here is a link:

http://herbiesaudiolab.net/gb.htm

[Gzerro]

Put a Rega RB303 arm on the VPI. That would be a hell of a deck, IMO.

ner

I would love to try this, but don't think this is easy to do.

Here is a quote from Stereophile about trying the mount a Rega 300:

"The solid-plinth Scout starts life as a sheet of 1 1/8"-thick MDF, machined to shape and finished in semigloss black. Most of its underside is covered with a thin steel plate for rigidity and damping, the latter thanks also to a thin layer of silicone sealant. The right-rear corner is drilled with a 1"-diameter hole for VPI's standard arm-mount collar. A Rega RB-300, with its pillar diameter of 22mm (or just over 7/8"), will fit, but the VPI's platter is way too tall for the Rega arm by itself, even with the usual 1/16" spacer: If that's what you have in mind, you'll have to get a machinist to make you something special."

[neobop]

I have never used that adjustment, the counterweight which also sets azimuth is more straightforward to use with the SoundSmith Counterintuitive for fine adjustment. Damping various parts of the arm would be something to try, and wouldn't cost much.

Would herbie's thin grungebuster dots work, or is there something better to try?

Here is a link:

http://herbiesaudiolab.net/gb.htm

I'm not sure. The Herbie's dots look like they're designed for holding weight.  You'd probably make out better with Ear brand cut and stickem dots, bought here:
http://www.percyaudio.com/

In the mean time you could get a hunk of modeling clay (non-hardening) or Plasticlay or mortite (non-hardening caulk) and experiment.  Even though you don't use that O ring for adjustment it might still vibrate? 

Seems like you have the anti-skate within reason now.  I still think the continuing problem is with a sympathetic vibration(s) reflecting back.
The giant advantage of a unipivot is having one clear path for vibrations going from the cart up the arm tube to the pivot, but that can work against you if they go in the other direction.
neo

[robbiesurp]

The Classic sounds much better, I wonder why?

I didn't experiment directly between the Rega and VPI, but sitting on top of a Salamander Synergy rack on a suspended wood floor, the Classic was happier. When I had the Rega in my old place on a Solid Steel Target rack placed on a concrete floor, I was happy to not tweak the table.  My system is in the living room so i want to keep it looking acceptable. I think the Salamander rack is still giving me some isolation problems, but upgrading it to some thing better that's still aesthetically pleasing will be expensive. I've changed the rack feet out for Herbie's grungebuster sliders as well as tenderfeet and iso-cups under most components.