I can't run an external usb sound card for input with my AMP+. The sound card has been used without any problem in several other raspberry pi installations without the AMP+.
I get glitchy sound and sample drops so i guess it doesn't get enough power from the pi.
I'm using a 12v 5amp power supply. How big of a thing do I need?
This doesn't sound like a power issue. If the power supply is the problem, the Raspberry Pi would be unable to detect the card or at least it would fail to read data from the card, not just drop samples. Therefore this is most likely a software/CPU performance issue. While the card might work well without the Amp, there is more to to with the Amp enabled as both cards uses different and completely independent driver stacks.
What kind of software are you using to read data from your external sound card and how do you copy this data to the Amp output?
Best regards
Daniel
