I'm doing this project as a personal learning experience and plan to open-source everything (with the requisite disclaimer: if you build this and destroy anything, its not my fault)
Most of my design experience is in the digital realm. I'm trying to improve my analog layout and circuit design - please provide feedback! It is a dual headphone amplifier based on nwavguy's O2 amp. I wanted to make something nice for listening to music or watching a movie together in an airport / plane / quiet place. There are two headphone outputs with independent volume control and output-stage opamps.
Some notable differences: Only one 4556 opamp per output jack - so the potential output current per headphone jack is roughly 1/2 of what the O2 is capable of. Since this is designed to be used in portable situations where battery life is critical, I thought this was an OK concession. Use of surface mount components. This means thin film SMT resistors such as RT0603FRE07100RL and others from that series in the signal path. I was really excited about getting an initial prototype built, so I omitted some of the more practical features present in the O2 such as:
- switchable gain
- wall power
- low voltage battery protection: this device could become dangerous near the end of uneven battery discharge
- power LED indicator
- the ability to remove power from one of the headphone output stages (n/a to the O2)
Bill of Materials
Bottom layer is a minimally interrupted ground pour.
I'm getting 3 boards made by oshpark.com. They are being fabbed as we speak!
Edited by gastro54 - 5/26/13 at 2:26pm