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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 6 responses by lewm

lewm
12,432 posts
 
We've heard from everyone but the OP.  Have you done any of the recommended experiments and what were the results?  Inquiring minds want to know. Thanks.
lewm
12,432 posts
 
CT0517, I have no dog in this fight, which is to say I am only guessing that the problem IS airborne.  I certainly could be wrong, since my opinion is based only on the paragraph submitted by the OP.  But can you say why you think the problem IS NOT airborne, with such conviction?

Rotarius, There is no harm in trying the cover, I agree.  But in general, I would never run any turntable with its dust cover in place.  This is based on trying it both ways, over many decades and with several turntables. Could it help in this particular instance? Maybe.  Anyway, trying the cover would tell us much about what is going on; if the cover makes a difference (for better or worse), the problem probably IS airborne.
lewm
12,432 posts
 
Totem, You wrote, "Start with implementing room treatments rather than
applying this or that band-aid."  Isn't there an internal contradiction in that sentence?  Some would classify room treatments as a bandaid. Not that there's anything wrong with that.  The simplest first steps would be to make small changes in the positions of the speakers or the turntable, respectively, and determine what that does.  Such experiments cost nothing.  The OP has such plans afoot, I should hope.
lewm
12,432 posts
 
No cover.  The cover itself will resonate, if the issue is airborne, and could make matters much worse.  As a general rule of thumb, I would never ever use a cover during play.  The stylus/LP interaction itself elicits vibrations that are best dissipated, not trapped under a cover.

Having said that, try it. I am interested to know whether my negative feelings about covers are operative in this instance. I have five turntables and none of them has a cover except the Kenwood L07D, which has a clever lucite, LP-shaped cover that sits down over the spindle directly on the mat and not over the whole top surface.
lewm
12,432 posts
 
I am not sure I agree with all the discussion about what is and is not a good isolator, BUT in this case I think the problem is air-borne vibration, not mechanical from a shaky floor up through the stand and the shelf.
lewm
12,432 posts
 
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.

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