Please ignore the mess, and the bottom-left pot did nothing.
What a mess! I didn't have enough time to learn kiCAD nor enough money to have it properly printed at the time, but as a proof of concept, it worked. I was digging through my old hard drive and I came across my old college capstone project. It's been a while since I had a chance to look at it, so I'm wondering if anyone could point out things I could do to improve on it.
I named it the amplifizer since it's comprised of a preamp, EQ, and a headamp. The concept was that you could power it off a single-rail +5V 250mA USB port, plug an audio source into it, and have fun! I used the Wurth Electronik WE-EPLE USB connector since it had an integrated EMC filter, the Semtech SC632A helped normalize a constant 5V flow, and the TI LM2663 gave me a -5V rail to have more flexibility with dual-supply op amps given my power constraints.
I don't remember why I went with a cascading TI OPA1644 preamp design as it's probably overkill for something like this. I used the TI OPA4376 for my EQ bands, and Analog Devices AD8655 in class-A to drive my headphones. The TI TLE2426 was a simple virtual ground solution that just worked. As you can probably tell, I'm a novice coming back to this, but I thought it would be cool to revisit and hopefully improve after all these years later. Any questions or advice would be greatly appreciated. Thank you for your time!