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-   -   balanced volume control (http://www.diyaudio.com/forums/pass-labs/5790-balanced-volume-control.html)

skaara 6th September 2002 06:46 PM

balanced volume control
 
How can I make a volume control with one pot (or attenuator?) for both channels of bosoz running balanced (now im using two 5k stereo pots of not so good quality)?
I searched forum but I didnt found answer to this question or It was there and I didnt interpreted it right so im sorry if that has been talked before.

stefanobilliani 6th September 2002 06:49 PM

You must find a quadruple pot :bigeyes:

Peter Daniel 6th September 2002 06:53 PM

Instead of placing the pot between output and ground (4 needed) place the pot between positve and negative output of ea balanced channel (2 needed), so one stereo pot would work. This way, depending on impedance of the pot, positive and negative output will cancel each other without conecting to ground. You can find this setup in Pass D1 DAC.

jwb 6th September 2002 07:08 PM

You can use Peter's idea but be aware that it can change the character of the circuit. Look at the original BoSoZ article. The distortion is related to gain, and using a pot between the two sides of the circuit changes the gain.

On my BoSoZ I used a four-deck stepped attenuator from GoldPoint.

Gabrielshorn 6th September 2002 07:11 PM

Peter,

Is that option for a stereo pot in the BOSOZ schematic as well? I seem to remember that being built in to the design.

Any idea on what resistance value to put there? Any pro/cons to doing it this way?

I am thinking now of getting an Electroswitch 4-pole 23 position switch and making a 5-10 kOhm attenuator and putting it at the output, seeing as all the IC-based pots have built-in opamps, or require an opamp.

Peter Daniel 6th September 2002 07:22 PM

Quote:

Originally posted by jwb
You can use Peter's idea but be aware that it can change the character of the circuit. Look at the original BoSoZ article. The distortion is related to gain, and using a pot between the two sides of the circuit changes the gain.

On my BoSoZ I used a four-deck stepped attenuator from GoldPoint.

The gain pot is the separate pot. The pots I'm talking about are at the output.

skaara 6th September 2002 07:24 PM

Ill check if I can get quad-pot here..

Peter Daniel 6th September 2002 07:27 PM

Is that option for a stereo pot in the BOSOZ schematic as well? I seem to remember th
 
I don't think it was discussed in the original article. What I'm suggesting here is a quite clever way of using single stereo pot to control balanced stereo output. I can only see pros (since pots don't even have to be matched perfectly) and none of the cons. Yet, this method is not very popular with DIYers, anybody knows why?:scratch2:

Peter Daniel 6th September 2002 07:28 PM

Quote:

Originally posted by Gabrielshorn


I am thinking now of getting an Electroswitch 4-pole 23 position switch and making a 5-10 kOhm attenuator and putting it at the output,

How much is it?

Gabrielshorn 6th September 2002 08:01 PM

4 deck 23 position electroswitch $59.95


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