Balanced active tone control

[mashaffer]

Just curious...

I have seen folks doing all balanced systems from input through PP output stage but was wondering whether anyone has seen or done such with active balanced tone controls in the pathway. I can imagine passive ones that short between the two legs but active is a bit harder to visualize.

mike

 

[Ketje]

The problem is tandem potmeters are that equal, you have to do the control with switches.
Mona

 

[legendre]

The problem is tandem potmeters are that equal, you have to do the control with switches.
Mona

I believe what Mona means by 'switches' is that due to the difficulty in obtaining properly matched tandem (stereo) control pots, you'd need to use stepped switches with precision resistors to keep the channels in-line with one another. Likewise, the associated components would need to be channel-matched as well.

There are other ways to do tone shaping in balanced circuits as well. As you mention, using a control or control+cap to short between the K and/or A of a bal. stage is one approach.