My USB/COX DAC board
 

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.

DAC circuit

Power supply

Re: My USB/COX DAC board
 

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.

Yes, I have replace the OPA2134 to Discrete OPA

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

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.

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

board I came up with
 

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.

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 +/-