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Old 4th August 2008, 11:26 AM   #1
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Default 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.
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Old 15th August 2008, 08:09 AM   #2
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DAC circuit
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Old 15th August 2008, 08:12 AM   #3
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Power supply
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Old 15th August 2008, 09:37 AM   #4
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Default 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.
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Old 15th August 2008, 10:18 AM   #5
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Yes, I have replace the OPA2134 to Discrete OPA
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Old 18th May 2011, 06:34 PM   #6
udailey is offline udailey  United States
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Do the transistors in the power supply need to be matched or do we get away from that with the trimmer?
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Old 24th May 2011, 05:46 PM   #7
udailey is offline udailey  United States
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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.
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Old 25th May 2011, 01:33 AM   #8
wgxold is offline wgxold  China
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Oh, this design is so cool. I want to know the size of the board.
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Old 25th May 2011, 01:44 AM   #9
udailey is offline udailey  United States
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Default 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.
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Old 25th May 2011, 01:46 AM   #10
udailey is offline udailey  United States
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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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Last edited by udailey; 25th May 2011 at 01:56 AM.
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