Feedback Through Turntable

jcoat007 · « **on:** 9 Jun 2003, 11:21 pm »

For a few brief hours on Saturday, I had the house to myself and was able to really turn up the wick on my system. The problem is that I started generating feedback as I turned it up. The louder it got the more feedback was produced. I was using my turntable, and I didn't experiment with the CDP to see if the same thing happened. I am thinking this is being caused by the needle picking up vibrations in the air, but I really don't know what is causing it.

Anyone else have this happen?

What can I do about it besides turn down the volume?

Malcolm Fear · « **Reply #1 on:** 10 Jun 2003, 04:39 am »

What sort of turntable? What is it sitting on? How far away from the speakers?

jcoat007 · « **Reply #2 on:** 10 Jun 2003, 01:25 pm »

Here is my setup. I have a Music Hall MMF-7.

As you can see, it sits on top of my rack. I purchased an extra shelf for my rack and sat the extra shelf on top of Herbie's Audio Lab Tenderfeet. The rack is spiked into the floor. Thoughts?

Psychicanimal · « **Reply #3 on:** 10 Jun 2003, 02:13 pm »

Quote from: jcoat007

For a few brief hours on Saturday, I had the house to myself and was able to really turn up the wick on my system. The problem is that I started generating feedback as I turned it up. The louder it got the more feedback was produced. I was using my turntable, and I didn't experiment with the CDP to see if the same thing happened. I am thinking this is being caused by the needle picking up vibrations in the air, but I really don't know what is causing it.

Anyone else have this happen?

What can I do about it besides turn down the volume?

Those belt drive units were not designed for real world music playback.

Sell the Music Hall, get a Technics 1200, do the mods and forget about feedback.

Read DJ Donovan's contribution to the KABUSA Fluid Damper review:

http://forum.audiogon.com/cgi-bin/frr.pl?raccs&1033259530&read&3&4&

jcoat007 · « **Reply #4 on:** 10 Jun 2003, 05:41 pm »

Quote

Those belt drive units were not designed for real world music playback.

Sell the Music Hall, get a Technics 1200, do the mods and forget about feedback.

I'm not trying to be a smartass, but are you saying that all belt drive turntables are crap

How does the belt drive cause feedback?

Psychicanimal · « **Reply #5 on:** 10 Jun 2003, 05:56 pm »

Quote from: jcoat007

Quote
Those belt drive units were not designed for real world music playback.

Sell the Music Hall, get a Technics 1200, do the mods and forget about feedback.

I'm not trying to be a smartass, but are you saying that all belt drive turntables are crap

How does the belt drive cause feedback?

I just wrote what I wrote. Those belt drives were not designed for real world playback, much less in a setup like yours. Period.

The belt drive system has nothing to do with feedback resistance. That has to do with the TTs suspension and its construction. The Sota Sapphire and above are belt driven and you can pound the chassis with a hammer.

I think the Rega's, Music Hall, Project, NAD, entry level SOTA's, etc are overrated units that just don't cut it under real world conditions.

nathanm · « **Reply #6 on:** 10 Jun 2003, 09:59 pm »

What does the feedback sound like? It would be cool if you could make a recording of it and post an MP3. I'd be curious to hear it since I can't turn up the wick enough to make my TT feedback!

Have you tried removing the clear lid? I haven't had much experience with them myself, but I would guess they would sympathetically vibrate quite easily. Just a guess... Otherwise, moving the TT farther away from the speakers would be best. I would move the whole rack to somewhere behind or to the side of your listening seat. Of course, this would necessitate longer speaker cables and depending on your views about those things this prospect might be cost-prohibitive.

Maybe try the 'ol half-inflated bicycle innertube with a board on top isolation thingy?

Have you tried listening with headphones?

And get some artwork on those walls fer crying out loud. How drab! I see an Epson 1280 there, so ya got no excuse!

Malcolm Fear · « **Reply #7 on:** 10 Jun 2003, 10:42 pm »

I forgot to ask - what type of floor - wood, concrete etc.
I use a Linn Sondek. The suspension isolates it nicely from feedback. I used to own a Luxman turntable that was prone to feedback. I ended up mounting it on a shelf, that was secured to the wall. That fixed it. The feedback was coming from the springy wooden floor. I moved to a house with concrete floors. It worked nicely back on the floor.

I would be trying the following:
Try mounting the turntable on a cardboard box (a cheap version of a Dekstand).
Try a half inflated 16 inch bike innertube with a shelf on top (wood, breadboard, granite, Corian). Mount the turntable on top of the shelf.
Try a shelf mounted on the wall.

regards

jcoat007 · « **Reply #8 on:** 10 Jun 2003, 11:13 pm »

My room is on the second floor of my house. Carpet over plywood over floor joists. The floor is remarkably stable. My kids jump around in there and the record player never skips. Either does the CD player for that matter. In my old house I was in the basement on concrete floors, and had no problem there. I turned up the wick quite often in that room and never had any feedback problems.

I have been thinking about the wall shelf and I may try that. I usually take off the TT cover, but during that listening session I was lazy and just tilted it back. Hmmm...coincidence?

Maybe what I should try first is some different isolation for that top shelf. Some type of metal cone or something. I have some innertubes lying around somewhere because I tried that method previously on my CD player. The problem with the innertube is balancing the unit because not everyhting has even weight distribution.

Can't afford the long speaker cable run. Haven't tried headphones, but intend on getting a pair. Yes I need artwork. I'm trying to convince the SO that we need to meld artwork and room treatments. I'm not getting anywhere with this one yet.

What does it sound like? It sounds like low bass feedback, not the screetchy high pitched feedback you would get from an electric guiter. It starts to build in this low rumble kind of hum that gets louder and louder as it feeds on itself. I have to turn it down when it starts becasue I'm afraid of what it will do if I let it just keep going.

Thanks for all of the info and suggestions so far. I really appreciate it. I would hate to think that I can't crank my system when playing vinyl. It deserves to be heard at maximum levels.

audioengr · « **Reply #9 on:** 11 Jun 2003, 02:37 am »

Do you have a tubed phono stage?

These have really high gain, so the tubes can develop microphonics. IF so, you should try tapping on the tubes in the phono stage to see if you can hear the thumps in the speaker output.

Psychicanimal · « **Reply #10 on:** 11 Jun 2003, 03:04 am »

Dude, you like to POP UP THE VOLUME!

Wrong turntable. Lesson learned. Put it up for sale...

jcoat007 · « **Reply #11 on:** 11 Jun 2003, 11:27 am »

Quote from: audioengr

Do you have a tubed phono stage?

These have really high gain, so the tubes can develop microphonics. IF so, you should try tapping on the tubes in the phono stage to see if you can hear the thumps in the speaker output.

I'm using an eAR834p. I have added some damping sheets to it and use Herbie's Hal-O Tube Dampers. Dead quiet when I thump on it.

jcoat007 · « **Reply #12 on:** 11 Jun 2003, 05:41 pm »

Quote from: Psychicanimal

Wrong turntable. Lesson learned. Put it up for sale...

I am thinking about selling it, but I thought I would give you first crack at it before I post it to the general public. It is in mint condition, but it is belt drive and prone to feedback in my room. On concrete it seems to works fine.

Let me know if you have any interest.

Psychicanimal · « **Reply #13 on:** 12 Jun 2003, 12:46 am »

Get a 1200 and do the mods or get a Sota Sapphire and your problems will be solved.

Your TT will sell fast. The audiophile crowd loves it! When you switch to something like the two suggested units you'll start reallizing how colored (I mean, "warm" sounding ) those glass and particle board TTs really are...

jcoat007 · « **Reply #14 on:** 12 Jun 2003, 01:07 am »

What do you think of this?

http://cgi.audiogon.com/cgi-bin/cl.pl?anlgtabl&1058972173

The only one on a'gon right now.

Marbles · « **Reply #15 on:** 12 Jun 2003, 01:47 am »

First, don't believe everything written here by "EXPERTS" myself included.

You have a nice table.

I heard a SOTA table just like that although I don't remember the arm or cartridge. It was in the CAR room at the MAF. If you look up the TNT review it might mention more about it.

The sound in that room was great. Keep in mind the STAR is the air vacume system SOTA uses.

At that level of table, the arm/cartridge will have a lot to do with how the overall sound comes through. I'm not familiar with either one, but that table is a very nice one.

EDIT: from the TNT report of the Classic Audio Reproduction..
This room was another wow moment. I was reallyhoping John Wolff was going to bring his TAD based Hartsfield's to the show, and he did. These are a classic JBL corner horn design that dates back to the late 1950's. These speakers are not only drop dead gorgeous, they sound even better. They flooded the room with fabulous music that was lighting fast and extremely dynamic. These were some of the best dynamics I've heard in a long time. If you have the $17,500 it takes to buy these, I guarantee you won't be disappointed.

The Hartfields were being driven by a pair of DeHavilland 845 SET monoblocks and just for good measure, John brought along a pair of Atmosphere M-50's. The pre was the Cello Audio Suite which was being fed from a SOTA Sapphire and an Accuphase SACD DP100 and the Accuphase DC101. I really wish I could have spent more time in his room. Who knows, maybe I can talk him into shipping me the Hartsfields for a review.........Like THAT's really going to happen !!!

me again..as you can see the CAR guys had no trouble using that table with some VERY nice and expensive gear....

Marbles · « **Reply #16 on:** 12 Jun 2003, 01:55 pm »

You might also want to contact Mgalusha and Wayne1 (Bolder) as they both have MMF-5's.

Mike made some tweaks to his table that Wayne liked, so Wayne made some of the same IIRC.

I have not heard them say anything but positive things about thier tables.

Psychicanimal · « **Reply #17 on:** 12 Jun 2003, 02:54 pm »

The "warm" sound of those glass and particle board TTs is due to vibration, both external and internallyt generated. For some people that's "nice" sounding. If you want neutrality and clarity I suggest something with a proper suspension, like the Sapphire and the creature on steroids.

You do need some artwork and acoustic treatments. Your system can't sound right the way you have that bare wall behind the speakers...

mgalusha · « **Reply #18 on:** 12 Jun 2003, 02:56 pm »

I can find plenty of things to say about the MMF-5 that I don't like but I don't have any feedback problems. I have a very similar setup to jcoat007 - same amps and speakers but my TT is about 15ft away from the speakers along a side wall. The side wall is right on top of the foundation and as such doesn't move much.

The motor in the MMF-5 sucks, it's noisy and not very smooth but it'll do until I can piece together a Teres.

I don't know if the MMF-7 has a felt mat but if so, replacing it made a large difference on the MMF-5. Wayne has some of the Herbies Audio Lab turntable mats and I have one of the None Felt mats. I am going to pick up one of his Herbies mats for a comparison.

Mike

jcoat007 · « **Reply #19 on:** 12 Jun 2003, 09:51 pm »

I did replace the felt mat with a Ringmat. It made everything snap into focus better. There was a general mushyness that was eliminated by changing the mat.