Turntable Rumble/Feedback

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!

Hi Abery, I meant to include that in my original post. I did remove the dust cover and the hinges are attached to it. Maybe slightly more volume before the feedback kicks in. Thanks!

Old Heavy, I’ll move the sub further away. It sounds great where it is, so will experiment a bit with further locations. I’ll be limited by the servo cord, but that’s pretty long as I recall.

Bill, that’s an awesome thread on JVC tables, thanks! Found this link several pages in. https://www.audiocircle.com/index.php?PHPSESSID=e63p7mektq0sg4pj9b66350af5&topic=89320.msg888202#msg888202 Modeling clay is cheap, I’ll pick some up. Yeah, the open design of the Mazings is probably not helping. I did have the same problem at about the same volume with the Vandersteens too.

Eric, I will check out whether or not there is speaker movement ahead of sound. I saw this filter, but it may be overkill compared to a $30 filter on Amazon. Or the Amazon ones don’t work well?

https://www.thecableco.com/rf1.html
 

The room is interesting in that the walls have an acoustic treatment on them. It’s a fabric with a think materials behind it. It was there when I moved in and I’m pretty sure the room was an office for the previous owner of the house. Not sure if it’s helping or hurting, lol. If you snap your fingers in the room there’s no reflection back to your ears, it’s pretty dead. I’ll read up on bass traps. Thanks again!

Based on recommendations here I ordered modeling clay from Amazon and will pack the open cavity in the plinth with it when it comes. I also moved the sub further away- about eight inches, lol. That’s as much as the servo control cable would let me move it, it’s not as long as I remembered. The sub is on a sheet of MDF and the MDF is on sorbothane feet, I suppose I could add an extra layer of each to try to further decouple. The sub crossover is set in the Velodyne controller at 85HZ and is not adjustable, unfortunately.  As for the Nobosounds, I had tried removing springs on the old rickety rack to no avail, it’s a good idea to repeat with the new rack to evaluate. Also, ordered a rumble filter. I appreciate the help here guys!

Eric,

Yep, it was used as an office by the previous owner of my home, so someone spent money I didn’t have to, lol. I do have a minidsp mic that I have yet to use, but have been boning up on YouTube videos to learn about it. The room may, in fact, be too dead but a measurement will help determine that. 

Slaw,

I just removed all but three springs in the nobosounds and that made a huge difference in volume ability before feedback! So, I’m definitely hearing an improvement, thanks for the suggestion! On the right track!

Greg,

Good catch on my typo in my original post, it’s a QL-5 or QL-50 depending on which designation you read on the table. I’m sure it’s an older unit, guessing nineties. I purchased all of the gear from my best friend’s estate after he passed and he was a big fan of 90’s gear.

Sweet sub with a ton of adjustment options, lucky guy. I did order a rumble filter that will hopefully be here next week. I think I can put that between the turntable and preamp only, but may experiment between preamp and power amp, not sure what would be best. I also ordered a minidsp 2x4HD so I can tweak my room, it’s something I’ve had in my mind for a while. Yep, mains are open baffle with long throw woofers, so not helping the situation, lol. 
 

Happy New Year to you as well! 

Old Heavy,

Actually, the servo cord is not a standard audio cord, it’s a five pin cord with a connection as pictured below. The manual does not mention an extension as available. I think it’s a standard five pin DIN so I ordered a 25 footer from Monoprice. Assuming that works I can move the sub far across the room. The later Velodyne subs used a phone cable as you noted. That will get the sub out of the way. If the mains continue to wreak havoc, I’m counting on the rumble filter and modeling clay to correct the problem.

Thanks,

Ken