I'm really curious of this attractive project. You promised to explain more on the choice of sampling frequency for the ADC@88,2kHz?
I like that You added. a loudness control.
What make do You use of the relays? I've never used relays in audio other than for output stage/speaker protection. I would worry the introduce hum from the coil?
The RPi Pico is an excellent choice. I guess You rip out the internals of a vintage, dated, integrated amplifier and use its controls through the Pico? I'd love to do that.
I like that You added. a loudness control.
What make do You use of the relays? I've never used relays in audio other than for output stage/speaker protection. I would worry the introduce hum from the coil?
The RPi Pico is an excellent choice. I guess You rip out the internals of a vintage, dated, integrated amplifier and use its controls through the Pico? I'd love to do that.
Thanks, I choose 88.2kHz for the ADC since it was two times 44.1kHz as used by AirPlay (Shairport Sync). I often use relays to switch input (no hum from coils since I separate relay power and ground from signal power and ground). I usually restore vintage gear but replacing the preamp stage with something like this is absolutely doable (if you don't care for the vintage gear).
This was just a proof of concept and I am still working on a real implementation. Most of the parts sources, new optimized code for the Pico is done, slimmed down Linux with CamillaDSP integrated as a service is done (running on a RPi Zero 2 W with the HiFiBerry DAC+ ADC on top). What is taking time is making a fully customized enclosure including custom made buttons. I will post the result if I ever manage to finish the build...
This was just a proof of concept and I am still working on a real implementation. Most of the parts sources, new optimized code for the Pico is done, slimmed down Linux with CamillaDSP integrated as a service is done (running on a RPi Zero 2 W with the HiFiBerry DAC+ ADC on top). What is taking time is making a fully customized enclosure including custom made buttons. I will post the result if I ever manage to finish the build...
In the Quad 44 preamplifier the cmos 4066 was used if my memory serves me well. I know there was some criticism but at the time miniature relays were expensive and not that reliable. Personally I couldn't complain about the sound of the Quad 44 but again, I can't afford being a top tier audiophile.