USB 3D sound card fix


USB 3D Parts

I bought 3 of these USB 3D sound card’s for a wireless music streaming router I am working on.
I plugged one in and it was running in seconds, the first thing I noticed was how bad it sounded then my earphones got hot.
I looked at the voltage output on the left and right channel and saw just over 2v DC on both.

Time to take this thing apart!

What I found was missing DC blocking capacitors. C9 and C20

USB 3D C20_uncut USB 3D C9_uncut

Note that C9 and C20 have been shorted on the PCB so you need to cut the track . See below.

USB 3D C20_cut USB 3D C9_cut

Now its time to add a capacitor to each side to block the DC voltage.
I used 16v 100uF electrolytic capacitors. This is just what I had to hand and they are small enough so I can close the case back up.
I tested another sound card with a 220uF capacitor and it sounded the same. So anything 100-220uF should work fine.

Note the capacitor polarity. C9 and C20 are marked with + – on the PCB. They are infarct wrong. The + on the capacitor should be connected to – on the PCB.
You can put the capacitors on the top of the PCB and solder on the underside.

USB 3D Fixed

That’s it.. Put it back together and test.
No more DC on either channel and it sounds much better.