HQ USB to SPDIF Circuit Design???

Hello there!

There are several chips which do just that.
One example is Texas Instrument/Burrbrown's PCM2906 - very nice device.

Its a USB audio codec, including stereo analog in and out, aswell as SPDIF in and out.


I've designed a PCB for it, which gives pretty nice performance :)
Its based on the circuit straight from the datasheet.
Its dead silent,- i tested it on professional studio powered monitors, and with the volume all the way up, there was 0 noise.

I have spent a considerable time on getting it that way, and came to the conclusion that the key for this, is to NOT to connect the analog audio in and out GROUNDS with the rest of the systems grounds at all. This way u have a "floating" ground, where the analog IN/OUT grounds, get their GND path thru the device to which you are connecting this circuit, ie. an amplifier, mixing desk, mic preamp, etc, and this way the fast speed digital gnds dont introduce noise into the sensitive audio signal.

I've used normal size resistors and capacitors as its a bit difficult to get them surface mount here, but I am pretty sure that the performance will be far better if SMT passives are used.

Also, when I built this device, I also built the little enclosure from wood, and I had to screen all of the enclosures walls, with sheets of metal, interconnect them electrically and ground them.
Without the screen a lot of noise was introduced in the analog input section, with the screening it was reduced considerably.

Ok thats it.
I hope it will help you anyhow in whatever you are trying to achieve.

Good luck!


  • pcm2906 usb soundcard.zip
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