Ah yes, I noticed and corrected the capacitor polarity issue on the breadboard implementation. However, I ran into some trouble getting an actual output out with these c-media usb interface chips (the cm108 is especially bad). So I moved on to using a cheap soundcard commonly available through aliexpress and maybe local vendors which utilizes the cm6206 (blue 5.1 soundcard from aliexpress) audio interface chip. Turns out these chips are designed to take in mic level inputs so the second amplification stage may be completely unnecessary in the original design. The non-faraday caged audio output seems promising but the AC mains hum is prominently present in the output after inspection through an Audacity spectrogram. I'll provide more updates as soon as I get a proper soldering station to wire up a perfboard implementation. As for the +/- 15V the supply voltage was basically DC (from oscilloscope readings) after being filtered by some bypass capacitors and low pass filters. I will definitely add a ground plane in the final PCB implementation.
Best regards,
Timothy Aguana
Timothy Aguana