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
Just by bad luck, your turntable may be sitting in an energy hotspot, despite your best efforts to avoid feedback.  Sometimes moving the turntable a few feet from where it is sitting will make the difference.  Trial and error.  Re-positioning the speakers, by even a few inches, may help as well.

As lewm pointed out could very well be a room issue, If you walk around the room, even behind your speakers do you notice any exaggerated 
frequencies?
Does the the issue arise even when not using the sub?

Room treatments may be the solution or hold on to your hats
adding another sub, as in "distributed bass" and room mode
anomalies.

 


@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