Questions about DC coupling and my USB DAC

Russ White · 10th August 2005, 07:06 PM

I have designed a simple circuit for the PCM2906 USB stereo CODEC.

I would like some reasurance that my output is not DC coupled. Sorry if this has been covered somehere, but I can't find it.

Cheers!
Russ

paologatto · 10th August 2005, 09:47 PM

Good choice! The PCM2906 and the OPA2353 sound very good together.

About the DC coupling in output, I suggest you to place in the schematic and PCB the space for the output capacitors.. if you see that there is no offset you can safely remove the capacitors and replace them with wires.
I have not studied your schematic, but remember that you are supplying the opamps between GND and 5V..

This is how I realized more or less the same schematic (with also input buffer and regulator):

(click to enlarge)

(click to enlarge)

Bye,
Paolo

Russ White · 11th August 2005, 12:49 AM

Quote:

Originally posted by paologatto
I have not studied your schematic, but remember that you are supplying the opamps between GND and 5V..

This is how I realized more or less the same schematic (with also input buffer and regulator):

Yes, that is why I wondered...

But, the inverting inputs to the opamp gates are polarized by C11 and C17. So I was hoping that would nullify any DC on the output..

I guess I will just have to do as you say and check.

BTW your DAC is very nice!!!

Good work!!!

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10th August 2005, 09:47 PM	#2
paologatto diyAudio Member Join Date: Jun 2004 Location: Italy	Good choice! The PCM2906 and the OPA2353 sound very good together. About the DC coupling in output, I suggest you to place in the schematic and PCB the space for the output capacitors.. if you see that there is no offset you can safely remove the capacitors and replace them with wires. I have not studied your schematic, but remember that you are supplying the opamps between GND and 5V.. This is how I realized more or less the same schematic (with also input buffer and regulator): (click to enlarge) (click to enlarge) Bye, Paolo

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