Turntable Rumble/Feedback

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

Wait, so this happens with the turntable NOT spinning? Is it more of a hum? If so, the issue you have is hum + feedback. Eliminate the hum problem (ground loop issue) and then worry about the feedback issue.

If on the other hand the problem arises ONLY from music, or moving around the room, then the problem is purely feedback.

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!

Have you tried to remove dust cover AND hinges(assuming it has hinges

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!

Some JVC turntables have a fairly thin plinth top that seems to pick up vibrations from music playing. Here is a link I started awhile back for JVC TT owners.

There is some talk of filling the underneith of the plinth with modeling clay to dampen the plinth.

For some reason I could not edit my post. Anyway, I have a set of Carver Platinum Amazings, the 4 bass speakers in those panels are open in the back so a lot of bass is being projected rearward. Might not be helping you any.

BillWojo

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.

If you see it in your speakers before yo hear it, it's infrasonic noise.  Definitely need a rumble filter.

That room also desperately needs diffusion behind the speakers and bass traps in the corners.

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!

Have you experimented with removing some of the springs in the Nobsounds? They will be more effective when around halfway compressed. 

I agree that you could use some bass corner traps.

I had almost this exact same thing, only my rack is a lot more massive so mine wasn't as severe. But same exact thing. Right down to Nobsound under the turntable. 

Problem is different things isolate at different frequencies, and Nobsound are not effective enough at this frequency. Replaced them with Townshend Pods, and that was the end of that.

You might be able to get away with moving the Nobsound to under a sub and using Pods under the turntable. But as severe a problem as yours might well call for the Full Monty of speakers on Podiums, subs on Pods, and turntable on Pods.

I would try slaw suggestion first, remove some springs it looks like your Nobsound could be compressed more. This will shift the resonant frequency lower, possibly low enough to suffice. So try it. But don't get your hopes up. Mine were optimized, still no luck. Nobsound are great for the money, but just not in the same league as Pods and this is one of those areas that highlights the difference.

Looking at the pic, to me it just looks like a whole lot of vibration going on in a confined space. Is the hardwood floor on concrete or is there a basement, crawl space underneath? I know it would be a pain, a rug or runner underneath your rack and sub could not hurt. Double check your sub crossover to make sure its as low as possible for your speakers. You have some big ol' speakers and subs moving a lot of air in that space. Keep curtains closed. What would happen if you moved your rack to in between the main speakers? 

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..

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!

There is some talk of filling the underneith of the plinth with modeling clay to dampen the plinth.

Are you sure that you listed the correct model number for your turntable?  I searched on Google and couldn't find it.

If it is an older JVC model, the above "fix" may be very beneficial. 

I have a JVC QL-Y66F.  It's a beautiful table, but the plinth is super resonant.  I stuffed a few pounds of plasticlay inside and replaced the feet with feet from MNPCTECH.  When I first got it, it howled like a banshee.  After taking those two steps and also putting it on a Symposium Ultra platform I could play it as loud as I wanted with no issues other than a little woofer pumping at high volumes.  That was with a Rythmik dual 15" F25 sitting literally right next to it.

Oh, sounds like the room may have been used as a meeting or conference space. Lucky duck!!

Then don't add bass traps without measurements. :) You may be OK, but the room may also be too dead.  If there's no diffusion you are going to get a very headphone like presentation.

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.

My other suggestion would be to remove the stock feet altogether if you have no clearance issues.

Might try some Nobsounds under your sub.

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.

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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 2015

The 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

Something to try: Move your sub up between your speakers and turn it on its side facing forward. Just as an experiment. It might not energize your floor as much.

russ69 they work from 18-85hz there is NO rumble filter cut. The factory solution "in the manual" was to give the sub a 25 foot extension cable for phono. READ what they said. LOL  BTW it didn't come with the cable it was optional for phono use..

Regards

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

I don’t have any great insight into the nature of this problem. I find it curious. But my rule is never to put in filters or other symptomatic relief, there will always be unintended consequences. I would recommend working until finding the root cause and fix that. I might have had some problem very early on, but if so it is lost to my poor memory.

Many years ago, I owned a Velodyne ULD15 II. Fortunately, it had no issues and the bass was just the way I liked it. I have owned other subs, but hadn’t been totally impressed until I bought GR Research with a 12" bass driver and a 300 watt plate amp. The GR has the needed options for any situation.

Back to the OP first post, remember he is saying this problem happens ’even when the 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?

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?

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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

Sounds like it is a feedback loop between the cartridge through the system back to the cartridge. Sounds like the JVC turntable is a rebranded pioneer PL-50. I would guess it is the turntable. I would trade it in and get a more contemporary turntable. There are really good ones available. I think this has a very high probability of solving the problem and increasing the overall sq. 

JVC didn't rebrand other tables. They were a top engineering company that designed their own tables and built some high end TT gear that is very desirable even today. They also designed and built some world class tonearms along with supplying motors and drive electronics to Micro Seiki.

For some reason most of the JVC tables shipped to the US had light weight plinths, they can be prone to feed back. In Japan, a lot of the upper tier JVC tables used constrained layer plinths, very massive and heavy. My guess is it added a lot to the cost to ship the better tables over here.

BillWojo

Just a guess, but I'm thinking you should use only 3 springs per corner for that turntable- and maybe only 2! I see all 7 in the picture, so even after taking some out you probably need to remove another 1 or 2.

The Nobsound should be compressed to only about 1/4" space, and the turntable bounce very slowly when adjusted right.

Then take the removed springs and use them under the sub. Use a 1/4" drill bit to make divots for the springs like the Nobsound feet. Use wood, MDF, anything to hold the springs. You will probably have enough but if not order another set because isolation is the solution to your problem and the sorbothane just ain't cutting it.

Ultimately your best will be Pods, a lot better than Nobsound, and Podiums under the speakers. This won't just eliminate the rumble it'll greatly improve all aspects, like a new system.

oldhvymec,

  Yah, I agree with the cartridge being a transducer, like a mic. 

 There was a moving iron cart that I had recently that caused a hum problem just due to the fact MI carts are more prone to being affected by AC fields. They also can lose their strength over time, which means that you will be turning up the volume and noise is higher because of it (at least with the phono pre I had at the time). 

  So some here are thinking about the TT itself having an issue, and others say cart. There were other thoughts as well, and I hope each can be eliminated or somehow realized that there may be a combination of devils. This is a good thread to follow. It is bound to lead somewhere should the OP pursue it.

BIG_GREG "I have a JVC QL-Y66F.  It's a beautiful table, but the plinth is super resonant.  I stuffed a few pounds of plasticlay inside and replaced the feet with feet from MNPCTECH.  When I first got it, it howled like a banshee.  After taking those two steps and also putting it on a Symposium Ultra platform I could play it as loud as I wanted with no issues other than a little woofer pumping at high volumes.  That was with a Rythmik dual 15" F25 sitting literally right next to it." 

Thanks Greg , I've had the JVC QLY-66F since 1982 when I bought it new. It seems to rumble more as it gets closer to the spindle, I was hoping I could adjust the tracking angle to raise the bottom of the Clearaudio Maestro V1 body a wee bit.
Think it may be too close. My table is sitting on a slate bar about 3 feet from my JBL 240Ti, but the angle of the drivers is not facing that table
I am going to take a look for the feet you recommended. And clay I've enquired about getting a new plinth  but seems the layout is too difficult to adapt according  to the custom shop I contacted so clay it is. thanks for the tips.