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Here's a problem for you TT gurus to solve! (I'm stumped!)


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OK, so this arvo I was over at @djb's, mounting his Stanton 'WOS CS100' onto his newly arrived Magnepan Unitrac arm.

 

David has 2 arms on his TT, which feed into different phono stages.  So he can select which combo he wants to listen to by using the 'Source Select' switch on his preamp:

  1. is a Grado Reference Master, on an SME 3012.  This feeds into an early version of my SLA-powered, JFET-based "Muse" phono stage.
  2. is the Stanton / Magnepan Unitrac (unipivot).  This feeds into a Hagerman Bugle phono stage.

 

Now, as organised above ... the sound from each cart is wonderful! :thumb:

 

But if we plug the Stanton/Unitrac combo into the Muse phono stage ... we hear a peculiar echoing warble to the sound.  There's definitely something wrong!  :(

 

But what can it be, given:

  • the Stanton/Unitrac combo into the Bugle sounds great - so the problem would seem not to be the Stanton cart or the Unitrac arm or the arm wiring?
  • the Grado/SME combo into the Muse sounds great - so the problem would appear not to be the Muse phono stage?

 

Now I know this is a 1st world problem ... but David would like to plug the Stanton/Unitrac into the Muse - as this is probably the best combination.

 

Any suggestions as to where the problem lies?

 

Andy

 

Edited by andyr
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I had a similar problem with my unipivot arm (Kuzma stogi s) on a Stabi TT, when it was mounted on a DIsc of silence suspension spring isolation system.  Drove me nuts as i tried to debug the problem, all failed, until i just removed the discs under the isolation platform.  Me thinks (just guessing here) that unipivots and suspension a bad combo?

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34 minutes ago, katattack74 said:

I had a similar problem with my unipivot arm (Kuzma stogi s) on a Stabi TT, when it was mounted on a DIsc of silence suspension spring isolation system.  Drove me nuts as i tried to debug the problem, all failed, until i just removed the discs under the isolation platform.  Me thinks (just guessing here) that unipivots and suspension a bad combo?

 

Rest assured - suspended decks and UPs work just fine.  And I have exactly the same Stanton/Unitrac combo on my own suspended deck.

 

Andy

 

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29 minutes ago, Wimbo said:

Did you try swapping the Phonos around? As in move them and also swap them in the Preamp. Sounds like something is exciting  the Unitrac.

 

Mmmm, don't quite follow your logic, Wimbo?

 

If "something is exciting the Unitrac (arm)" ... then shirley it would still be exciting it when that arm is plugged into the other phono stage?

 

But it sounds fine!  :(

 

Andy

 

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9 minutes ago, andyr said:

Mmmm, don't quite follow your logic, Wimbo?

With a problem like this,things need to be moved around.Just like lowering noise floors or hums by moving cables.

It sounds to me that the Unitrac is being excited by something which is making it Warble. You know that Electrical energy is mechanical energy and so maybe where the Muse is located is causing the problem with the Unitrac.I'm most probably totally wrong, but changing the scenario might help.

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Thanks, John ... but but but ...

 

16 minutes ago, Telecine said:

Possible problems:

 

1. Acoustic feedback

 

The TT and arms were not moved - so they stayed in the same place.

 

If this weird echoey sound is due to feedback - shirley it would be happening irrespective of which phono stage the Stanton/Unitrac is plugged into?

 

Quote

2. Resonance issue

 

If it's a resonance issue between the Stanton and the Unitrac:

  1. Why don't I hear it on my TT - given I use the same arm & cart?
  2. Shirley the problem would still be there, irrespective of which phono stage the arm is plugged into?

 

Quote

3. Vibration problem

 

Ditto.

 

Quote

4. Input overload causing clipping on the phono stage.

 

Yes, that's certainly a valid suggestion.  The Stanton is, I think, 5mV - whereas the Grado is only 4mV.  And it's the Stanton into the 'Muse' which is causing the problem.

 

But but but ... when the Stanton was mounted on David's OL-1 arm (before the Unitrac arrived) ... it was plugged into the Muse.  Which suggests overload is not the problem.  And, as I said, I run the same Stanton/Unitrac combo with no issues.

 

 

Regards,

Andy

 

Edited by andyr
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7 minutes ago, Wimbo said:

With a problem like this,things need to be moved around.Just like lowering noise floors or hums by moving cables.

It sounds to me that the Unitrac is being excited by something which is making it Warble. You know that Electrical energy is mechanical energy and so maybe where the Muse is located is causing the problem with the Unitrac.I'm most probably totally wrong, but changing the scenario might help.

 

Sure, W, I agree that you can often solve problems like noise floor or hum by moving things around.  But we "solved the problem" (of the strange echoey noise when using the Stanton/Unitrac) by simply plugging its phono cable into a different phono stage.  No physical re-arrangement was needed and the phono stages, arms etc. all stayed in the same position.

 

And the Muse phono stage is SLA-powered BTW - no mains cable, no power transformer.

 

That's why I said I was stumped!  ;)

 

 

Andy

 

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21 minutes ago, Telecine said:

5. Poor cartridge alignment ;) 

 

Mmmm - if it's poor cart alignment ... why does it sound great when plugged into the Bugle, instead of the Muse?

 

Andy

 

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1 hour ago, andyr said:

 

Mmmm - if it's poor cart alignment ... why does it sound great when plugged into the Bugle, instead of the Muse?

 

Andy

 

 

What is the input sensitivity on each of the phono stages?

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1 minute ago, Telecine said:

 

What is the input sensitivity on each of the phono stages?

 

 

Very good question.  I know the gain of the two phono stages (the Bugle is a lot more than the Muse) but I don't know the input sensitivity of either.

 

What is the definition of 'input sensitivity'?

 

1 hour ago, Full Range said:

 

May have something to do with the load switch setting on the offending phono amp 

 

 

There are no 'load switches' on either phono stage.  These are both MM phono stages with a default load of 47K.

 

Andy

 

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41 minutes ago, aussievintage said:

Maybe one phono amp has a lower/different low frequency response, allowing acoustic feedback where the other one doesn't? 

 

Very interesting suggestion.  :thumb:  The most likely one, yet!  :D

 

I will have to think more about what you said.  Maybe the Bugle has a rolled-off bottom end which 'solves' a feedback problem which the Unitrac arm has, in David's environment?  Which I don't have in my environment with the same arm and cart ... and a later version of the Muse?

 

Andy

 

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46 minutes ago, andyr said:

 

Very good question.  I know the gain of the two phono stages (the Bugle is a lot more than the Muse) but I don't know the input sensitivity of either.

 

What is the definition of 'input sensitivity'?

 

 

There are no 'load switches' on either phono stage.  These are both MM phono stages with a default load of 47K.

 

Andy

 

 

Have a read here to gain an understanding of the issue, then use the calculator:

 

https://www.kabusa.com/pregain.htm

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1 minute ago, jrhill said:

It wouldn't be something silly like a ground/shield different connection?  Maybe something so obvious that ... 

 

Of course that is possible.  But:

  • the 'echoey' noise goes away when the arm's phono cable is plugged into a different phono stage, and
  • this 'echoey' noise is not the kind of thing (IMO) associated with grounding issues?? 

(The earthing wire from the Unitrac/Stanton was attached to the ground terminals of both phono stages.)

 

Andy

 

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What would Andy do with out me, the customer from Hades?

Spend time with his family?

Im sure his wife thinks I'm  an excuse to visit his mistress ....Maggie 

 

He misrepresents the second phono as a Bugle it is so modified by Andy that it is a Bugle Muse or a Muse Bugle ! If I had him change the power supply to a battery version it might be better than the Muse .

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