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Feedback through turntable

My system consists of a McIntosh C2300 preamp, MC452 amp, MCD500 SACD player, VPI Aries 3D with Ortofon Cadenza MC cartridge, Manley ChinookSE phono stage, PS Audio P5, Sonus faber Cremona Auditor M speakers and REL B1 Sub bass system.  My issue is with turntable use only; SACD has no issues.  On my pre when volume is +55 (peak at 45watts) I start to get feedback through the turntable - a sort of low freq sound, back off volume and it goes away.  My Auditor M speaker is about 3 ft away and in front of turntable.  I do have a rumble filter (KAB) installed between preamp and phonostage to help with sub woofer pumping.  Due to room layout I cannot rearrange the setup/move turntable.  My turntable is on a 2.5" block of wood and that sits on 4 isolation blocks via spiked feet.  Any thoughts how I can eliminate this problem?  Harry Weisfeld with VPI states he has 4 15" woofers (JBL Everest) near his Prime Signature setup with no issues at all.  Why am I having this problem and how can I eliminate it?  Thank you in advance for all feedback.
miner42
geoffkait's avatar
geoffkait
23,365 posts
 
Just to mention the roller bearing assemblies actually provide very good isolation in not only the horizontal plane (all horizontal directions) but also the three rotational directions - twist, roll and rock, as a consequence of the shallow cup and bearing motion when forced, which are also important since the seismic vibration produced by Earth crust motion, traffic, etc. arrives at the house or building in the form of waves, like waves on the ocean passing under a boat. My first product, the Nimbus Sub Hertz Platform, isolated in all six directions and had a resonant frequency as low as 0.5 Hz!

miner42 OP
709 posts
 
My main listening room is on the second floor, carpeted on a suspended subfloor.  I do not have the luxury of moving the sound system away from the speakers due purely to room size (15' x 15' x 8') and layout (open on two sides - second floor game/media room).  I feel my table is shielded from mechanical vibrations.  The VPI Aries 3D has the mini-HRX feet, this sits upon a 2.5" layered birch platform with a cork top which is on 4 isoblocks that sit on my marble-topped audio console.
ct0517's avatar
ct0517
2,041 posts
 
My main listening room is on the second floor, carpeted on a suspended subfloor

Is the 1st floor,  the main house floor also suspended ?  Do both floors use horizontal wood beams? 
slaw's avatar
slaw
23,825 posts
 
miner42,

Did you ever try ct0517's dance tip? If you are embarrassed to dance, follow his directions without the dance. If you're getting the low frequency noise this way, something in your tt isolation chain is not set-up right or is not able to isolate effectively for your particular situation.

What type of audio console are you using?
slaw's avatar
slaw
23,825 posts
 
If you haven't already watched the Townshend Audio YouTube video showing how a speaker on a concrete floor reacts to vibrations, you should. (bdp24 has talked about this in other threads).

Then think about if a speaker on a concrete floor has this much vulnerability to vibrations, surely your tt on a second story will be magnified multiple times over.

Food for thought.
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