A little help needed with Audio Note balance set-up in SEX 2.1

[Karl5150]

Using the Stereomour II balance scheme that worked well in the Quickie, I decided to replace the 2 mono pots in my SEX 2.1 with the same set-up.
I purchased AudioNote  balance and volume pots and wired them up like the S-II and Quickie.  The volume pot works as expected.
With the balance pot at the center detent there is no sound. Turning it all the way to the right brings the left speaker up to full volume, and vice-versa.
Several net searches have been fruitless. I was hoping someone with experience with the AN products could weigh in with some info.
TIA, Karl

 

[Paul Joppa]

Neither SEX 2.1 nor Quickie have two controls, so I am guessing you have modified those amps?

There are many ways to make balance controls that are not the same as a simple linear potentiometer, as used in Stereomour 2.0. Perhaps the AN is an example? The spec of +/-6dB suggests that it is. A quick google search did not provide any further information on that question; maybe another forum member will know.

 

[Karl5150]

Thanks for weighing in Paul.
The SEX 2.1 was built as a speakers-only amp, the dual-mono was my first attempt at balance control, using the headphone jack location for the second pot.
The Quickie was built into a custom top plate with cut-outs for volume and balance after I had built the S II.
Foolish me for thinking everyone would use the same, simple, off-the-shelf style balance scheme the BH crew used.
I'll try hitting up AN for some product support. In the meantime if any other bottleheads have experience they can share I'd be grateful.     

 

[Paul Birkeland]

Can you send a link to the AN balance pot that you bought?  It could be an MN taper pot, which needs to be wired up differently than the SMR2 configuration.

 

[Karl5150]

Paul,
Although I purchased it from some of our common friends up north, this is the item
https://www.hificollective.co.uk/potentiometers/audio-note-100k-balance-potentiometer.html.

 

[Paul Birkeland]

That datasheet is not very helpful.

If the pot is an MN, it will have very low resistance between the center lug and one outer lug for half the rotation, then increasing resistance between the center lug and the other outer lug for the other half of the rotation.  This operation will be mirrored on the second deck of the pot.  This would be consistent with zero output in your setup with the pot centered, as the pot would be shorting everything to ground.

One option you have is to get a 100K linear pot and put the MN pot in your parts stash.

Here's an image of how your current balance pot could be wired.  Those two lugs that are grounded need to be the ones with high resistance to the center lug on each deck.  This type of balance pot should come before the volume pot.  There also needs to be a resistor in series between each input of the balance pot so the balance pot has something to work against.  (100K should do it)  There will be a fair amount of insertion loss with this setup.

 

[faskenite]

Well this has been timely information!  I purchased an Audio Note balance pot as well for the current Stereomour II build I have under way, mainly because I used an AN volume pot on a Quickie and have been happy with it.  I haven't wired the balance pot up yet, and given this new information and especially the bit about insertion loss, I think I'm going back to the stock balance pot.  As an alternative, is there a balance pot out there that is wired and functions just like the stock pot but may be preferable to the stock pot for any reason?  Or would the differences be insufficient to matter?

 

[Doc B]

If you want something preferable to the stock controls in a Stereomour II I would suggest getting the MourQuiet upgrade. It will outperform pretty much anything else.

 

[Karl5150]

Paul- Ill give that a try. Thanks
Doc- My MQ for S II arrived last week- Once I get the new pots in the  SEX 2.1 sorted it will move to the top of the list.
Thanks for all the feedback.

 

[faskenite]

Karl is braver and clearly more capable than I am. It’s back to stock for me, at least until the upgrade bug pays its next inevitable visit.  Thanks for raising this Karl, and thanks to Doc B et al. for the education.

 

[Karl5150]

Paul, thank you, the diagram was the ticket. I had checked the resistance on the pot and figured out that the two decks were opposite, but my pea-brain couldn't translate it to red and black wires. On to the MourQuiet.
Faskenite- I don't know if these AN pots will offer any sonic advantage over the stock set-up in the S II, the volume/balance scheme designed to mitigate the low volume mismatch in the stock volume pots. As the BH crew is fond of telling us - try it and see. The diagram Paul provided will get you there. You could listen for a while before taking the MQ plunge. Good, better & best? You could report your findings and add to the knowledge base.
Thanks again everyone.

 

[Paul Birkeland]

What did you end up using for series resistance between the center pins of the RCA jacks and the inputs of the balance pot?

 

[Karl5150]

I used 43K, I'm getting about 95K centered and about 46K and 95K biased.

 

[faskenite]

OK I sure would like to see this.  Karl, could you possibly post a picture of the balance control as wired with the resistors?  And a question for the Bottlehead Braintrust:  if I were to use the AN balance control, would I have to reverse the positions of the volume and balance controls on the Stereomour II chassis?

 

[Paul Birkeland]

  And a question for the Bottlehead Braintrust:  if I were to use the AN balance control, would I have to reverse the positions of the volume and balance controls on the Stereomour II chassis?

You'll have to be the one to answer that.

 

[faskenite]

Back to the stock balance control!

 

[Karl5150]

faskenite, I put the resistors up at input RCAs, the SEX was getting pretty crowded down by the pots. Not a practical solution for the S II with 3 sets.

 

[faskenite]

Got it, thanks. I’m going to do the AN volume pot and the stock balance control for now, with a view to renovating with a MourQuiet later.  I suppose I shouldn’t tweak at all since I’ll be lucky if I don’t blow the SII up and me with it, given my skill set.  But I can’t resist!