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
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 |
I can’t get over how close that type of sub is, to the rack and it’s NOT decoupled. It’s on a mat? That won’t work. That type of sub rattles the heck out of the floor plane, the one that is CLOSE to your TT. Bla, Bla, Bla everyone, that won’t work, I don’t care how it sounds, "it sounds best there", that does not mean it sounds good at all. There is ZERO dampening in that set up. Everything is going to vibrate. It’s not hard to SEE if you just look. No carpet, traps, drapes, and then pack a sub right next to the rack.. There I said it.. Sorry if I hurt anyone feeling.. LOL Like I give a crap.. Ground up, not paint first.. It’s like talking about 600 horsepower engine in a car with a flat tire and a broken windshield. Fix the flat and the glass, first.. Mercy. Happy new year.. |
You see that rumble filter on the plate? Rythmiks plates offer a few more options, I guess. I'm using GRs but they use Rythmik plates. Darn near bullet proof. Very versatile. I do like the finish on that sub you have though. The rumble need to be on the mains, not the sub. Still makes me wonder without one on a servo and the software doesn't understand "rumble" that could be a problem. GR took vinyl into account. Your mains are open baffle woofers, right? They usually have a bump @ 40hz and down, I didn't even think of that.. That type of speaker is going to be more prone to pumping. Trying to dig decent bass out of the system might be a little tricky with vinyl. In non servo bass heavy systems, I've got a few, I just CUT 40 hz down. Most of the vinyl especially pre 70s the bass is cut pretty high anyways. All the 78 are cut higher than that.. It's just not on the media. The actual mechanical "Rumble" on my new Thoren is so low they don't even publish it. But it will sure act up without a lot of work or very little work and a rumble filter.. LOL Happy New Year |
3) Cable kit with 25' phono cable for connection from controller to woofer cabinet, and a 3' patch cord for connecting the controller to your pre-amp. Speaker wire is not included. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>> This is from your manual. It couldn't be clearer what the longer cable was for. There is NO rumble filter consideration with this old servo unit.. WAY ahead of its time, but a guy that tried to fix one moved on the Rythmik, it was funny at the end of the article 3 or 4 months later. Progress March 2015The amplifier and speaker have moved on to the next owner. They were replaced by a Rythmik Audio subwoofer. I cracked up.. Sure take care of your stuff though.. Hats off for sure.. Regards |
TT is OFF.’ Motor off, that is, stylus laying in groove I assume. Wouldn’t that mean that the cartridge is not sending signal to begin with? <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>> The TT motor is off the cart is still live. It is a transducer, you bet that’s the culprit. Blow on it, you’ll see. I have a couple MC low output carts. You plug in a 20:1 SUT, look out.. You have to be very careful with bass. Blow stuff up, pumpin’ those OB Carvers. The woofers have bump stops, but that won’t stop the overshoot. back and forth.. Voice coils get HOT anyways, with those old voice coils.. It’s more than just a little problem.. Regards |
