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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 9 responses by miner42

miner42 OP
709 posts
 
Thank you to everyone who has contributed their thoughts.  I will start by removing the cones and allowing the platform to sit directly on the isoblocks. I will also move the right speaker a bit at a time to see if I can eliminate those airborne vibrations.  I think I know the answer but will ask anyway - would keeping my acrylic cover on during sessions help or hinder my issue?
miner42 OP
709 posts
 
I will be trying positioning the speakers and moving the TT a bit.  The more I think about this the more I feel the problem is airborne.  I may go as far as plugging the rear ports on the Audito Ms first to see if that helps.  Thank you to all who have contributed.
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.
miner42 OP
709 posts
 
I have moved my speakers and sub (crossed at 49Hz) to the adjacent wall - this has helped.  My sub is now approx 15' from TT and furthest speaker cable is 20' from amp.  I made some temp cables using 14/4 in-wall cable to try the relocation prior to outlay of a pair of 20' speaker cables.  without the REL engaged I can now pump the volume up with no feedback (one of my Sf Cremona Auditor Ms is 5' from TT); once I engage the REL I need to adjust the gain to keep from getting some feedback at louder volumes.  So, this does enforce the thought the problem was acoustic and not mechanical.  No shared beams between TT rack and REL now.  Next, I may try putting the REL on a 3" maple base.  Jim Pendleton with Osage Audio has been very helpful and spent many hours helping me tame this wild dog.  I will also replace the OEM inserts on my TT feet with the Symposium inserts.  Thank you everyone for your suggestions.
miner42 OP
709 posts
 
Listening room is on a second floor; suspended floor.  Main floor is a concrete slab.  I have done the dance thing around my TT and no problem with noise coming through speakers.  If I yell/scream into my cartridge I do hear a sound through the speakers.  As mentioned, I have now relocated my speakers to the adjacent walls and the REL to the adjacent wall, too.  REL is approx. 16.5' from TT; nearest speaker is 5' from TT.  I can play with monitor only with no issue but once I introduce the REL I need to turn gain down to reduce feedback as volume is increased.  Crossover is set at 49Hz on REL with 180° phase.
miner42 OP
709 posts
 
...and I did remove my KAB RF-1 filter and noticed the music is much more 'cleaner'; that filtered appeared to be adding noise to the music.  Downside is the woofer pumping is back during TT usage.  I will have to monitor the gain and find a happy medium.
miner42 OP
709 posts
 

No issue when sub is out of the picture.  I have moved the sub to a location 15' from the TT to a non-corner in the room.  At high volume I still get some feedback thru TT but, at a higher volume than before.  I have moved my speakers, also, perpendicular to the component rack.  My speaker cables are 8m in length now.  My next experiment will be putting the sub on a platform.


miner42 OP
709 posts
 

I can but WAF won't allow.  Plus an +85 lb TT on a wall rack - would not feel comfortable.


I put the REL B1 on an isolation base and this even helped more.

miner42 OP
709 posts
 
Feedback does not happen when sub is out of the loop.  I do realize the inserts on the mini-HRX feet are rubber - still contemplating replacing those with Symposium inserts.  One other point of contention - the bearing/bell housing on the 3D arm.  I am told the base of the bell housing (where the uni-pivot fits into on the arm) needs to be no more than 1/4" from top of armboard/VTA adjustment base.  Mine was considerably more than that (3/8" approx.).  I lowered mine and readjusted the VTA to bring arm back to parallel with platter then did the fine adjustments.  I was told by VPI the higher the arm is above the VTA base the more unstable it is hence a target for airborne freq.  I have also relocated some equipment and moved sub away from the TT.  All seems well for now.  I guess having my TT set up professionally when I bought it was not the right choice.
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