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Rumble question- Thorens/black widow

Hello, I've been a reader  for a while but this is my first post. Thanks in advance for any help/advice!

my turntable makes a very soft rumble sound mostly audible between the tracks or in very soft passages of music. I know the noise floor will never be like a cd but I would like to address this as I don't hear it in my previous  turntable which is a cheapie. 

I have a thorens td125mkii w an infinity black widow tonearm. I suspect the sound is actually due to the tonearm. That's because it seems to be microphonic, because if I gently rub my finger on any part of it, you can hear the gentle rubbing sound get picked up. This is the first black widow- it doesn't have damping trough.  

-do you think the rumble is from lack of damping or maybe not?
-can I diy damp the arm easily to test it?
-or what else might be the problem? It has original wiring but theres no hum or feedback at all. 

Thanks and sorry if this post was long!
-David 

128x128mugrug12
tubegb's avatar
tubegb
190 posts
 
It may make sense to address the motor noise/vibration first? Admittedly it has been a long time since owning a Thorens turntable, but I don’t recall it having as much audible noise as you describe.

 

The first generation Infinity Black Widow tonearm with knife-edge bearings requires the use of a low mass/high compliance cartridge for it to perform at its best. (Back in the day think Micro Acoustics, ADC, Grace, etc.) I would not recommend a “home brew” damping strategy. This does not necessarily address your issue but should provide the opportunity for best tonearm/cartridge performance.Watch those original wires, super fragile as you probably already know.


mugrug12's avatar
mugrug12 OP
10 posts
 
Thank you guys...

the cart is an ortofon super om30. I just got an nos adc xlm ii so I can see if that makes a difference but it seems like it's the arm. For instance if I lift the arm and gently slide a finger down the tube with my other hand I can hear the sound of the finger running come from the speakers. Is this the kind of microphonics that damping mitigates?

the motor doesn't really make noise. Your ear has to literally be an inch from the pulley w no platters on to hear it. I figured that was par for the course, is that wrong?

Dave 
yogiboy's avatar
yogiboy
5,664 posts
 
That Ortofon is a good match with that arm,here are the results from vinyl engine,a perfect resonance of 11 hz.
The problem is not with the arm and cartrige compatibility!  https://www.vinylengine.com/cartridge_resonance_evaluator.php?eff_mass=3&submit=Submit
mugrug12's avatar
mugrug12 OP
10 posts
 
Yes- The music itself sounds awesome and i think w the xlm mkii it will be even better.  I just think the noise floor should be lower. Is tomearm damping strictly to fix resonance from the music, or is it also for mitigating mechanical vibes from the turntable itself? Could it be damped externally somehow?
mugrug12's avatar
mugrug12 OP
10 posts
 
I think also maybe I don't fully understand the purpose of tonearm damping. If the mass/compliance is well
matched producing the correct recosnance, like my setup is, then what's the damping fluid for on the later models?
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