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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

Showing 4 responses by rotarius

rotarius
431 posts
 
@miner42, you are not isolating anything with rigid materials like brass cones and spiked feet. Once you realize that most of that is useless BS, you can start to look at real isolation methods. Browse through some industrial catalogs and look at how isolation feet are designed and what materials they use. See how sensitive lab equipment is isolated.
http://www.newport.com/c/vibration-isolators
rotarius
431 posts
 
If you have sound waves affecting playback, the cover should help (I doubt that though).  It should not be a hindrance  either way.
rotarius
431 posts
 
Some strange replies posted here.  There is no harm in using a cover during play to see what the results will be, so why not experiment?  As for standing waves, resonance etc., it is all very dependent on that particular system of components and materials, impossible to predict by anyone and I am sure most people giving advice here have never used a vibration analyzer, they just go by their perception.  Try everything you can, experiment away:) 
rotarius
431 posts
 
My tonearm is only 32" away from my speaker but slightly behind the baffle. There is no issue with feedback at all.  Airborne seems unlikely from my experience. 
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