Hi Jonathan.
I'm pretty much deaf, but even then I've not needed full volume. Raj's improvements to quality could even lessen the need. Given that, I've not needed any more than the pin3 mod - and isn't pin 6 the Vcc supply to U1? Are you sure you're not messing with pin 7? or 2?
You seem to have the CAD usable, how about this? - CW sidetone is possible by resistor (1k or so?) from pin 3, with another from there off to the raduino pin giving the tone. Audio in from the Volume control wiper is then to the 2N2222 collector point. The 2N2222 clamps the Rx audio on PTT - it should be pretty much instantaneous, and any 'pop' there will be from the remnant Rx audio level. Those 2 resistors are then a voltage divider? feeding the sidetone. U1 is, of course, powered on Rx, and the CW mod will have it powered also on TX - I don't operate CW so I haven't explored this. ON PTT release there may be some 'pop' as U1 powers up - it will only take a few milliseconds, and we can delay the 'let-up' of the 2N2222's clamp by a small cap across the (10k) resistor feeding its base. T=CR so ~10 milliseconds per microfarad.
In short, I'm wondering if there is any real need for that second 2N2222?
Hopefully helpfully,
73 de ZL2DEX
