[Sonny]

  I am going to add my own 2 cents here and you can do with it what you will.  In sorting out cartridges to use with my Black Widow tonearm I ran across a few that were very microphonic and some that seemed totally devoid of that artifact.  What you are dealing with is based mostly with the cartridge.  Without the needle on the record what you are getting is feedback into the motor of the cartridge and some cartridges are prone to do this.  I choose to not use cartridges that are prone to this.  It may be amplified by some other factors like damped/undamped tonearms but always starts with the cartridge, it is built in per se.  The cartridge designers are well aware of what they are doing and choose this if it suits them to get the sound they want. 
  To give an extreme example I had two different ADC XLM II improved cartriges that were so microphonic that with the arm locked its holder I could lightly rub the wires leading from the cartridge and the sound from the speakers was almost the same as touching the stylus, a Shure V15 III was also not that great. On the ADC I thought I could mount a stylus on the body of the cartridge and play records. A  Denon 301 II and AT 33EV had no feedback that I could detect.  My Empire 2000/E III is absolutly dead quiet.  I also had an opportunity to demo a Soundsmith Carmen and it was dead quiet also so I ordered a Soundsmith Boheme to get the line contact stylus and ruby cantilever. Still waiting on the SS.
Walt

Walt, thanks for your insights...the question is if you had your cartridge down on the LP, is it still quiet?

T

[neobop]

Thanks all for the comments...but remember, what I am saying is that with the cartridge on an LP, on the platter at higher than normal listening volumes, I get the "sound" of the knocking on the platform to come through to the speakers.  I don't think this has anything to do with resonance, but rather that the sound of the "knock" as you will, a good knock, is ricocheting through the MDF platform, up the plinth/platter and picked up by the cartridge that is ON the record on the platter.  I don't know of any table, that if you had the cartridge down on the record, turned the volume up higher than normal listening volumes (85db and above), knock on the rack or turntable platform and not hear and "sound of the knock" being amplified through the speakers.  I guess the key here is, with the music playing, with the "pressure" of the sound waves created by the volume of music coming from the speakers, going to make the platform, plinth, platter, tonearm and so forth amplify that through the music???

I think this and if the cartridge skips, that is the issue...

T

It can be hard to tell if you have very low level acoustic feedback. Feedback is what you're describing. Sometimes it can sound like a subtle smearing. Perhaps knocking on the platform induces a physical shock that goes beyond what would be encountered by sound pressure waves? The most extreme high end tables now come with a dedicated stand. Maybe it's optional on some. I think this started with the Goldmund Reference that came with a dedicated stand the size of a small end table and was quite heavy. That platter was 35lbs. Anyway, there are two aspects of this, acoustic feedback and physical shock. Physical shock can come from structural aspects of your house (listening room) when vibrations are transmitted from the floor or walls to your table. I think you can modify the platform so that acoustic transmission is at a minimal level. However, if you knock hard enough to cause physical shock, those vibrations will be transmitted.
http://www.savantaudio.com/referett.html

http://www.needledoctor.com/Clearaudio-Statement-Turntable?sc=2&category=45

[Delta Wave]

If the platform is in two pieces you could try filling it with sand or lead shot (or sheet). I would definitely try to de-couple the platform as someone had mentioned earlier.

[Sonny]

However, if you knock hard enough to cause physical shock, those vibrations will be transmitted.
http://www.savantaudio.com/referett.html

http://www.needledoctor.com/Clearaudio-Statement-Turntable?sc=2&category=45

You're right, if I knock hard enough...but during normal listening, even at high level listening, is it a problem???  That's what matters I guess.

[ptmconsulting]

This "knuckle test" is rather pointless in real world conditions, but it does tend to point out where real world vibrations could possibly be mucking with the signal out of the cartridge. To that end I found the following to be extremely helpful in passing this test.

I built a sand box for the TT to sit on, actually a stand consisting of 3 sand boxes. Very heavy and very stable, and this mass helped enormously with the blackness and quietness and bass response out of my unsuspended torntable. But it still did not pass the knuckle wrap test.

I then built a poor mans Ginko Cloud by placing 8 squash balls on the sandbox/shelf with a piece of butcher block on those and the TT on that. This substantially reduced the sound of knuckle raps on the stand and the shelf from coming through the speakers. And it did not muck with the PRAT or blackness or anything else that I was getting before.

I highly recommend this method.

[Sonny]

If the platform is in two pieces you could try filling it with sand or lead shot (or sheet). I would definitely try to de-couple the platform as someone had mentioned earlier.

Dave, no, it's not, it in one piece, best I can do is drill into the 1.5" MDF some holes and fill with lead shots...then seal it with some silicone or something.  I can also get some rubber sheets with 70 durometer and put in under the plinth, tonearm pod and motor...
T

[Sonny]

This "knuckle test" is rather pointless in real world conditions, but it does tend to point out where real world vibrations could possibly be mucking with the signal out of the cartridge. To that end I found the following to be extremely helpful in passing this test.

I built a sand box for the TT to sit on, actually a stand consisting of 3 sand boxes. Very heavy and very stable, and this mass helped enormously with the blackness and quietness and bass response out of my unsuspended torntable. But it still did not pass the knuckle wrap test.

I then built a poor mans Ginko Cloud by placing 8 squash balls on the sandbox/shelf with a piece of butcher block on those and the TT on that. This substantially reduced the sound of knuckle raps on the stand and the shelf from coming through the speakers. And it did not muck with the PRAT or blackness or anything else that I was getting before.

I highly recommend this method.

Thanks, i think the sand box thing is a great idea...I just want to mod what I have and not have to build a new platform (i like the walnut trim).  Problem is, my plinth is already 130lbs, the tone arm pod, another 30lbs, the motor and platter, another 40lbs...all plus the platform, sitting on top of the Salamander Rack, any more weight and I believe the rack will collapse!
T

[neobop]

You're right, if I knock hard enough...but during normal listening, even at high level listening, is it a problem???  That's what matters I guess.

I agree!
I wonder though, if you might benefit from modifying the platform to some extent, as discussed. Even if you decouple the platform from the cabinet it's still coupled to the table. You could buy a bag of lead shot from a gun store or use sand to fill the underside of the platform. Didn't you say there was room under it? Drilling large holes and filling + a layer underneath should work good. I'm sure the Ginko type platform would be good, except each Ginko ball can support 10lbs. I don't know about squash balls. I also don't know if going much further than deadening the platform would do anything. Perhaps making a dedicated stand? If your cabinet/table is very stable now and you don't really have a problem, I wonder how much benefit. On the other hand, if your top-heavy set-up isn't very stable.....

You haven't discussed the table set-up in its entirety, specifically the stability of the cabinet with your massive table. None of us really know what it's like playing a record on your player. I suspect it's pretty damn good. 

[Sonny]

Anyway, there are two aspects of this, acoustic feedback and physical shock. Physical shock can come from structural aspects of your house (listening room) when vibrations are transmitted from the floor or walls to your table. I think you can modify the platform so that acoustic transmission is at a minimal level. However, if you knock hard enough to cause physical shock, those vibrations will be transmitted.
http://www.savantaudio.com/referett.html

http://www.needledoctor.com/Clearaudio-Statement-Turntable?sc=2&category=45

Regarding physical shock, if my table / rack is on concrete floors, there's not much physical shock to be worried about, however, I live on a busy street with trucks that frequent the road about 15 ft away, so the shock from the trucks could come through from the concrete up the Salamander rack, etc....no?

I guess, am I worried over "Spilled Milk" here?

[Sonny]

yes Neobop, it is currently very top heavy!  including the platform that the TT is on, I would say that above that 30" Salamander rack sits roughly 200 plus pounds, if not more like 250lbs!  The other items in the rack weighs about 30lbs, excluding the shelves and hardware.  I was thinking of putting some more equipment or heavier equipment in that rack.  Anyways, does the rack sway or jiggle when I move it?  Yes!!!

Last night I put a glass of water on the platter, knocked the platform "hard" and really no ripple to report, expect for the movement that was caused by the knocking on the platform (sitting on a top heavy rack) that caused the water to barely move back and forth.

If the TT was lighter, I would suspend it, etc...

I think I will drill holes in the MDF and fill with lead shots, then cover with another piece of something, maybe 1/4 acrylic.

Thanks
T

[TomS]

I am sort of going through a similar process. Non suspended TT with a slate plinth (70 lbs), 3 threaded brass cone feet resting in aluminum footers that have Sorbothane pads on the bottoms. The 3 TT footers sit on a thick granite top that is inset into wood frame (HHG Stand) of my equipment stand. The stand's legs then have threaded brass cones resting in the brass floor protectors at the bottom. My basement floor is concrete with Dri Core plastic/wood underlayment and 5/8" bamboo nailed down hardwood on top of that. The floor protectors rest on top of the bamboo.

Because my platform needs to be about 3" wider on top I am thinking about adding a 15x20x3 maple slab or a similar slate slab layer, resting on top of the inset granite.

I contacted Steve at Herbie's about various options and he recommended some interesting options that were not terribly expensive or disruptive. It might be worth it to see what he can offer.

In my case here is what he suggested:

(1) At the bottom of the rack legs, put his Fat Dots (dbNeutralizer material) on the bottoms of my existing brass floor protectors or just replace with his Fat Grounding Bases.

(2) Replace the Sorbothane between my wood frame and inset granite shelf with Regular Grungebuster dots.

(3) Use Thick Grungebuster dots between the granite and maple slab (or slate) top.

(4) Consider Iso-Cups and Iso-balls to replace the 3 brass feet on the plinth.

I'm going to give it a try. If it doesn't work on the TT I have plenty of other spots for those pads and such.

Tom

[neobop]

TomS,
I don't know what all of that stuff is. Just make sure the replacement feet can support the weight of the table.

It's great having a super heavy high end table; accommodating it can be a problem. If you've got a concrete floor, you're way ahead of the game. Dedicated turntable stands like the old Lead Balloon work best on concrete. If you've got wood floors, a shelf anchored in the studs usually works best.

I would look at systems or stands like this, to figure out the best way to go:
http://www.grandprixaudio.com/prod_monaco_mod.php

The dedicated stands for Goldmund and Rockport were simple and similar. The Goldmund stand was made out of steel and I think it weighed around 200lbs. It wasn't as tall as it looks in the picture, less than 2 ft. The Rockport stand was taller I think. These two 1 piece stands accommodated arguably the best tables ever made. It's not exactly practical to have a stand cast out of steel, but if you eliminate the joints you could have the top welded on or coupled with sorbothane.
http://www.savantaudio.com/arcleadb.html

http://www.enjoythemusic.com/sirius.jpg

Put your platform on something like that and you've gone the whole nine yards.

[Sonny]

Neobop, that would be great, all the stand suggestions you gave...unfortunately, i can' get anymore stands, there's no room and I've got a wife!  Though accommodating, I can't push it!   

[TomS]

...and they're a bit more pricey than decoupling products I suggested (maybe $100 worth) and work with what you already have. As I said, my floor is actually 2 layers of wood (floated) on concrete so maybe my situation is a little unique.

[Sonny]

...and they're a bit more pricey than decoupling products I suggested (maybe $100 worth) and work with what you already have. As I said, my floor is actually 2 layers of wood (floated) on concrete so maybe my situation is a little unique.

Tom, I think I have decided to try something similar, called "foamed PVC" sheets.  Will use it on the platform the put the TT on it.  I will also drill 1" holes in the 1.5" MDF and fill it with lead shots...

Then we'll see how it works out.
Thanks all!
T

[TomS]

Great thread. Let us know how that goes. I am hopeful the Herbie's stuff works out for my setup. I don't want a new stand either!

[Sonny]

Great thread. Let us know how that goes. I am hopeful the Herbie's stuff works out for my setup. I don't want a new stand either!

Sure will, just don't know when I'll get a chance to do it though...but in the meantime, enjoying the music!

[neobop]

I am sort of going through a similar process. Non suspended TT with a slate plinth (70 lbs), 3 threaded brass cone feet resting in aluminum footers that have Sorbothane pads on the bottoms. The 3 TT footers sit on a thick granite top that is inset into wood frame (HHG Stand) of my equipment stand. The stand's legs then have threaded brass cones resting in the brass floor protectors at the bottom. My basement floor is concrete with Dri Core plastic/wood underlayment and 5/8" bamboo nailed down hardwood on top of that. The floor protectors rest on top of the bamboo.

Because my platform needs to be about 3" wider on top I am thinking about adding a 15x20x3 maple slab or a similar slate slab layer, resting on top of the inset granite.

I contacted Steve at Herbie's about various options and he recommended some interesting options that were not terribly expensive or disruptive. It might be worth it to see what he can offer.

In my case here is what he suggested:

(1) At the bottom of the rack legs, put his Fat Dots (dbNeutralizer material) on the bottoms of my existing brass floor protectors or just replace with his Fat Grounding Bases.

(2) Replace the Sorbothane between my wood frame and inset granite shelf with Regular Grungebuster dots.

(3) Use Thick Grungebuster dots between the granite and maple slab (or slate) top.

(4) Consider Iso-Cups and Iso-balls to replace the 3 brass feet on the plinth.

I'm going to give it a try. If it doesn't work on the TT I have plenty of other spots for those pads and such.

Tom

Tom,
I went to Herbies site and saw a few of those items. I'm not really familiar with them so I can't comment. It's a little difficult to visualize your complete table/rack. Although both slate and granite have high mass, they're both good at transmitting vibrations if the whole structure is set in motion. In fact, their mass tends to make it worse. That makes the maple platform a good possibility, whether you use it instead of the granite or in addition to it. The wood has good damping properties in combination with other more massive materials like stone or steel.

If you look at the pics of the Lead Balloon, Goldmund and Rockport stands, the one thing they have in common is lack of joints and structural rigidity. Top-heavy can work if it's solidly planted and there is no movement between the parts. If any of the Herbies things allow movement I think they might be better elsewhere. To be honest, I don't think you need any of that stuff. I'd Pick out a nice maple (or whatever) platform and put some short cones (points up) under it, right on top of the granite.  If you're on a tall rack or cabinet that isn't stable, then abandon hope, all ye who enter here. 

Please let us know how it works out.

[TomS]

I don't want to hijack Sonny's thread but here is the rack and TT for reference. T, if you want me to start another I can do that, so just let me know.




With the rim drive, vibration from the motor pod must be prevented from going up to the plinth from the base supporting both. There is Sorbothane on the bottom of the motor base. The motor itself then pivots on 2 aluminum points in the base itself. The TT cones pointing down prevent vibration from traveling up to the plinth. The TT manufacturer found another layer of slate sitting on squash balls performed better than wood when using a wall mount.

I'm no expert in things mechanical, but it seems you make a choice between coupling (e.g. Sistrum, cones, spikes, etc) which uses mechanical diodes to send energy to a sink somewhere or decoupling (pads, sandbox, squash balls, etc) which turns the energy to heat.

Here is my simplistic view of what you have to deal with. There is a path for vibrations from the floor up through the stand, as well as a reverse path from the components on the stand to send energy back down. There are airborne vibrations entering the components from speaker output and the room itself that need to decouple or drain somewhere. The basic tool choices are to couple/drain one direction or the other, or you can use decoupling/damping methods, including high mass/rigidity methods.

The Herbie's generally provide decoupling which has worked well for me for speaker stands and electronics. It does require some application tuning based on the mass and vibration your trying to control on either side of each of the interface pads. It is the least disruptive and least costly to apply in my case so that's the route I'm going for now. If that all fails, then a wall mount is probably the next best choice for me.

The good news is that at least there is some very well known science to draw from for a change. I just need to understand how to apply it 

[jtwrace]

here is the rack and TT for reference.

That is sexy!