2. analog
  3. 128511-1637

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
raymonda
855 posts
 
I don't know why I assumed he had an integrated..........just run longer interconnects and keep your amp where it is.  

Having your turntable so close to the speaker is just not smart. Also, do not place your table in a corner after you move your system.

This is the best solution to your problem.
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. 
totem395
390 posts
 
lewm
"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.

I guess it all comes down to the proverbial "chicken and the egg"

If a room has particular issues ie modes that propagate and are not dealt with any amelioration down the chain is in my mind the "band-aid".
In a studio or other professional venue the first thing that's considered is the room, since that will always be the limiting factor for whatever follows.

Is the room in the OP's case the problem? The way to confirm is to run a sweep and determine where and why the anomalies are present.

Personally the whole room treatment subject is one of the most 
overlooked and discounted topics considering its effect on whatever 
gear, tweaks or changes follow. Thats my take on it.






bdp24's avatar
bdp24
9,703 posts
 
Todd, the Townshend Seismic Platform (the "original" Seismic product, which I have and use, not the current "spring-in-a-bellows" Seismic Pod design) actually IS a slightly inflated inner tube inside a metal frame. The top and bottom damped metal platforms are separated by the inner tube, and it provides, as you say, a lot of vertical isolation. I then have roller bearings on top the platform for the lateral isolation they provide. The combination works real well.
toddverrone's avatar
toddverrone
840 posts
 
@bdp24 ha, I had no idea. I have a teak cutting board on an inner tube.. 

Where did you get your roller bearings? I'd love to DIY, but I haven't found good cups.
More to discover