Negative voltage charge pump in audio circuit: how to remove background noise ?

[PCB.Wiz]

I'll try to make a test board using this design. However I would really like to do up to -20V to drive EM84 / EM87 tubes. I think is possible using a pair of SUPSiC GAQV1123S.
However, I'm a bit worried with the LED turn-on time of 0.23ms. Would your circuit still work by putting two 1123s in series with a 100 ohm resistor ? Will your circuit work with other classic OPAs ?

Yes, it should work in series, just scale the feedback resistor.

The GAQV1123S shows the active turnoff, which is more nuisance than asset in this use case, but the OpAmp makes operation more tolerant and linear.
If you have a signal generator, feed it with a triangle wave 10-25Hz and check the waveform.

[microvia]

I'll try to make a test board using this design. However I would really like to do up to -20V to drive EM84 / EM87 tubes. I think is possible using a pair of SUPSiC GAQV1123S.
However, I'm a bit worried with the LED turn-on time of 0.23ms. Would your circuit still work by putting two 1123s in series with a 100 ohm resistor ? Will your circuit work with other classic OPAs ?

Yes, it should work in series, just scale the feedback resistor.

The GAQV1123S shows the active turnoff, which is more nuisance than asset in this use case, but the OpAmp makes operation more tolerant and linear.
If you have a signal generator, feed it with a triangle wave 10-25Hz and check the waveform.

I added a typical schematic in my previous message.
I wish the VO1263 wasn't that expensive compared to the SUPSiC 1123S. The former can deliver up to -14.7V or-29.4V depending on where you pick the output voltage. The latter, which has the active turnoff, can deliver -12V only (-24V with a pair in series as in my previous schematic).
Still, this allows two magic eye grid outputs: one at the first sensor, the other at the second, hence two voltage ranges using the same duty cycle.
I don't have any AD8601 handy, only classic types used in Hi-Fi.

[PCB.Wiz]

I added a typical schematic in my previous message.

If you double the voltage, you would also double the feedback resistor (220k -> 470k ) as you want the same current operating points.