Turntable Rumble/Feedback


Hi All,

I have the following set-up:

Nakamichi Pre-amp

Krell FPB 600

Velodyne ULD-15 Sub

JVC PL-50 Turntable with Grace tone arm and Audio Technica Cartridge

Carver Amazing Speakers

I have been trying to unsuccessfully eliminate a low frequency audible feedback when attempting to play vinyl. If I turn the sub off completely I can play a record, but really no bottom end. The Velodyne servo control has a low pass filter that I think cuts at 85 hz before getting to the Krell. With the sub on, I can play very low volume. Turning the volume up causes an audible rumble that gets louder in a feedback loop.

I originally had the table on top of a rickety old component rack and figured that was a large contributor. I had racket balls cut in half under two layers of MDF and also a set of springs under the table feet to no avail.

I received a Pangea Vulcan rack for Christmas and filled the tubes with layers of wax, sand and wax to try to add damping and assembled it tightly. Just took it for a test spin and same result. I previously had a set of Vandersteen’s hooked up which behaved the same way in terms of feedback.

The sub is sitting on a layer of MDF that has Sorbothane feet under it. The rack and Carvers are sitting on a hardwood floor. The sub is only about five feet from the rack.

So, I’m looking for advice on how to eliminate this rumble/feedback. I read in another post about using a KAB RF-1 filter, but not sure it will work as appears the application is for woofer pumping subsonic. Was also thinking about a mat below the turntable, but not sure if that will help as if I tap on the Pangea shelf I am not hearing it through the speakers.

As a final note, the problem occurs not only when playing vinyl but also if the turntable is off and the needle is fist sitting in the groove, so should not be motor noise. Thanks in advance for any advice here!

Ken

 

ct-ken

A rumble filter and springs. 60.00 USD. Use ear plugs to dampen the itty bitty springs. Add 5 dollars for 20 pairs. :-)

Go servo bass and eliminate all the problems.. They can’t feed back or pump. They are made for turntables and the pickiest of bass heads..

Being BASS deaf don't count..

Happy New Year

Thanks for the reply Eric. I would not describe it as a hum. Whether playing music of the needle just sitting in the groove there no rumble or hum until it gets to maybe 1/4 volume. Then the woofers start oscillating and it gets increasingly louder until I turn the volume down. The preamp goes through the sub controller/amp and then into the Krell. If I turn the volume down on the sub all the way, I can play a record at any volume, just no lows due to the Velodyne controller cutoff. 
 

Here’s some pics of my system and components proximity to each other if it helps, excuse the mess. 
 


 

Old Heavy, is there a rumble filter you recommend? Happy New Year to you as well!