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Turntable rumble

Agaton Sax said:
I think even the Audio Research SP3 had one. Ingvar?
Click to expand...
No Johan, the SP3 did not have a switchable high pass filter, nor does my present SP6, on the other hand they have input and output capacitors so have a fixed filter but at a far lower frequency.

The GAS Thaedra has one, switchable from not engaged to 10, 20, 30 and 50Hz, this is before the volume control in the circuit so does not help when the output stage DC servo stops working so it can then produce some heavy DC output, but no rumble pass through.

A very long time ago, very long, when the first Rega Planar and Planet were introduced in Sweden and we discovered how feedback prone they were a friend got a good idea, a very good idea.

So we cut a piece of 18mm plywood the same size as the the Rega chassis and attached an 16" bicycle inner tube to that in a way gave it a "more or less" rectangular shape and inflated that, the Rega put on top of that, floating on the inflated inner tube, was totaly imune to feedback, that idea was later found in comercial gadgets, pretty expensive but still using a bicycle inner tube inflated between two layers of wood or plastic boards.

The tennis ball approach is good but only Dunlop Wimbledon grade balls work, no cheap Adidas balls.

Ingvar
 
@Ingvar Ahlberg & @Agaton Sax ,
I used 4 squash balls under a very heavy G.301 with "one half of the plinth", decoupling it from the bottom half ofnthebplinth. Bottom half was hard coupled resting on 4 custom made roller bearing feet (two clamshell parts with a bearing ball between them). You could play that monster on a train, zero mechanical or acoustic coupling to the environment.

But, as Agaton said, each TT is a different animal. Some like it hot, some not. Using a Technics SL1200 with spring loaded feet to test the playback environment for a hard coupled Clearaudio will produce no usable insight.
 
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Ingvar. There was a time when I had a custom made piece of MDF under each component. Each piece of MDF had three holes where the valves of three innertubes poked through and could be inflated thus. However coming to the Cary 805s in the morning to have them hanging at precarious angles,, threatening to break the very expensive 211 tubes from 1930 was too much for me. I used the inner tubes from the small wheels of wheelchairs and spending hours to find the right degree of inflation was too much



I still used tennis balls under a very sensitive phono stage but remembered a lecture from @ Schalk many years ago about destructive interference so now use Cardas blocks where once were tennis balls and those Finite Element feet elsewhere.

Actually I just became lazy. Anyway there is 400lb of sound proof "Fire Door" between eqp and vibes



Sorry Miles. Just to show we have all been down this road and are very familiar with your frustrations.
 
To try to be at bit more serious, nothing that comes easy to me, did You try with the obvious start, isolation/decoupling of the turntable?

The Clearaudio Concept weigh in at around 7-8 Kg so the Staedler erasor type won´t work but there are an imense amount of simple to try things to do before purchasing expensive feet or other gadgets like that.

The 16-18" bicycle inner tube is one very cheap, and effective first try, just inflate to ~2Kg and let the bottom of the TT float on that, feet not touching the shelf, if problem is still there You also have acoustic, airborne feedback but that sounds less likely.

You can also try with ordinary party/childrens baloons, inflate to a handball size, a lot less than maximum size, test, 4 baloons under the bottom of the TT, feet not touching shelf, do not use pink baloons, blue and red works best, green ok, pink also looks, well You know a bit".

If the problem is gone with the TT resting on air cushions You know the problem source.

Ingvar
 
But You did no tests with any kind of isolating/decoupling devices under the turntable?

There is no way You vcan get mechanical feedback into a streaming device,, what was the purpose of this test?

Ingvar
 
I told You pink baloons don´t work!

But seriously then it looks like acoustic feedback, in combination with mechanical, then better ask Mike, @fldlsys, he obviously has experience with this TT-Tonearm combination, problem is there in some way, mechanical feedback/disturbances does not travel through baloons, even if they are pink.

Ingvar
 
ghostinthemachine said:
What I see in that video is not rumble but arm/cartridge LF resonance. You need a phono-pre with a high-pass filter to counteract that.
Click to expand...
Or, attention of a very good TT fettler who will identify the cause and suggest a solution that will fly without having to low-cut the output. Different cartridge, arm setup, damped cartridge mount, etc.

If this was one of the old style tonearms that can be damped, no problem. Unfortunately that magnetic spring-hanger has its own mind. Not easy to troubleshoot.
 
As ghostinthemachine said that looks like resonance in the arm cartridge combination. Is the LP or platter maybe slightly warped?
 
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