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-   -   My USB/COX DAC board (http://www.diyaudio.com/forums/digital-source/127543-my-usb-cox-dac-board.html)

audio-gd 4th August 2008 10:26 AM

My USB/COX DAC board
 
2 Attachment(s)
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 15th August 2008 07:09 AM

2 Attachment(s)
DAC circuit

audio-gd 15th August 2008 07:12 AM

2 Attachment(s)
Power supply

analog_sa 15th August 2008 08:37 AM

Re: My USB/COX DAC board
 
Quote:

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 15th August 2008 09:18 AM

2 Attachment(s)
Yes, I have replace the OPA2134 to Discrete OPA

udailey 18th May 2011 05:34 PM

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

udailey 24th May 2011 04:46 PM

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 25th May 2011 12:33 AM

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

udailey 25th May 2011 12:44 AM

board I came up with
 
1 Attachment(s)
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 25th May 2011 12:46 AM

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 +/-


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