Open Source Headphone Amplifier

[blueskull]

Hi, I'm trying to build an amplifier for my Bladelius USB DAC and my ER4S. As ER4 series share the same actuator, differs in only cables, and the cable is interchangeable, I decided to make a BALANCED amplifier for my ER4. To make the amplifier more universal, I want to make a balanced or unbalanced input, balanced or unbalanced output amplifier, with over 120dB SNR and -120dB THD. While being HiFi, it should consume low power and be small form factor, to be fitted inside any currently available portable devices.
The circuit chosen is diamond buffer plus op-amp, the buffer is designed as the buffer used inside LME49600, and the OP is OPA1602. The attachment is the schematic of one channel. If anyone have any ideas, feel free to let me know.
Signal feeds from INN and INP, outputs from OLN and OLP. Power supplies are P- and P+.


License:
1. Redistribution of this circuitry or its related products must reproduce this license term, and declare that it is originally designed by GAO Bo, aka Blueskull, and this should not be used as any sort of advertisement.
2. This design is provided without any express or implied warranty. Licensees shall be responsible for any negative consequence included but not limited to personal injury, patent issue or property loss.

 

[blueskull]

Update 2013/JUN/14 4:38 GMT+8

Added power converter.
Added 2 MCUs.
Added Board-2-Board I/O connector.
Added mid point protection circuit.

This should be a complete system.

Attachments: All snapshots in PNG, exported project in PDF.

 

[blueskull]

Third Version

Third Version:
Bug fixes: Re-annotated some nets.
Bug fixes: Changed source voltage sampling circuit to save idle power.
Added: PCB library.
Added: Parameter annotation.
Added: Footprint specified.
Added: Extra input common mode filters.

Schematic drawn in Altium Designer 6.9.