Re: [Alsa-user] PCM2707C + PCM1794A Crackle Problem

[Daniel M. <da...@zo...>]

On 09/24/2014 09:30 AM, Dario Ernst wrote:
> i have built a "Jedac", a DIY-USB DAC consisting of TI/Burr-Brown
> PCM2707C for USB interfacing as well as the PCM1794A for the actual
> conversion. The original author has some more documentation including
> schematic and PCB-Layout here:
> http://users.abo.fi/jskata/JEDAC/
> 
> I've been using the DAC for a while now. Recently, i've noticed that i
> get a slight "crackle" in the background. Only when listening to music.

Please test this with aplay, and make sure you're using a file that is
in stored in one of the sample rates and bit depths the hardware
supports natively. This is to rule out possible resampler problems.

If that doesn't help, another debugging tip is to generate a wave file
that contains a simple 16-bit up-counter as audio payload. Play this,
and see whether you see a sane pattern with usbmon. If you can, tracing
the data on I2S is also a useful way that would show you whether the USB
stack in your device does the right thing.


Daniel