Replacing mono pots with stereo 100k in Foreplay III

[Ritchie]

I would like to remove the mono stepped attenuators and replace them with a 100k stereo stepped att.
I will be wiring the volume control in the normal position not the shunt configuration.
Is the 100K value pot ok in this circuit?

Thanks.

 

[Paul Joppa]

The 100K value is just fine. We use that value in the Quickie, SEX amp, Stereomour, and Crack.

Be aware that the maximum gain will increase by 10dB.

 

[Ritchie]

Paul,

I am assuming the extra 10 db is without the 33k resistors and if I left them in, it would be approx. 5db
increase at max. gain? Is this correct?

thanks.

 

[Paul Joppa]

Yes, that's correct. But if you are going to use a series resistor, even with a "normal" pot topology, I'd stay to a lower resistance, 50K or less. Otherwise you can get a high resistance before the tube at intermediate volume settings, and the Miller capacitance of the tube's grid will affect the treble.

 

[Ritchie]

Thanks Paul.

 

[Paul Birkeland]

Hello Ritchie,

I might also recommend installing some series resistance between the input selector and the input of the 100k pot.  In my personal preamps, I will often have a selectable resistance switched in here to get the best range out of the attenuator.

 

[Ritchie]

Yes, I was thinking of starting with the 33K series resistors that are already in the circuit.
I believe this should get me deeper into the 100K stepped attenuator I'm using.

Thanks,
Ritchie