My USB/COX DAC board

[audio-gd]

I have finished the test of my USB/COX DAC board, it use PCM2707 to decode USB, and DIR9001 to received the COX,
I use a AD1852 to decode the I2S signal, later I will send the circuit diagram, and welcome every body give me advice.

[audio-gd]

DAC circuit

[audio-gd]

Power supply

[analog_sa]

Originally posted by audio-gd
welcome every body give me advice.

Once i built something very similar. Replacing the opamp with a differential mosfet pair, like a Pass preamp was an obvious improvement.


I wish someone will design a usb dac using a better usb chip.

[audio-gd]

Yes, I have replace the OPA2134 to Discrete OPA

[udailey]

Do the transistors in the power supply need to be matched or do we get away from that with the trimmer?

[udailey]

Hoping someone might have an answer. I etched a board to try this circuit and want to get the best performance but not sure if matching is necessary.

[wgxold]

Oh, this design is so cool. I want to know the size of the board.

[udailey]

This is for the psu on the bottom of his 3 supply schematic. 100mmx146mm
Blue is top layer and green is bottom. When you see green disappear under blue its not the same trace but they are overlapping at that point.

[udailey]

hopefully someone will be interested enough to pop in and talk about transistor matching and if it is necessary on the +/- supply PSU.
I bought 50 of each small signal transistor and 10 of each larger transistor. Hope to not have to match them all, even though its not a real big pain. I imagine DC offset wont be a problem ;P but not sure what that trimmer does and want to make sure it does not make up for only small differences between +/-