[LAU] status usb2 for sound

[Martin Homuth-Rosemann]

Am Freitag, 6. November 2009 schrieb Arnold Krille:
> On Thursday 05 November 2009 23:40:43 Hartmut Noack wrote:
> > So again a last try: can anybody recommend any USB-interface recently
> > available for about 50 Eur/USD ?
> 
> I was going to recommend the edirol um22 like I own one. But then again you
> are probably searching for a usb-audio interface ;-)
> 
> Lets face it: in the 50€ range there is nothing to expect except for
>  behringer and maybe terratec. Both cheap and noisy as hell. And not really
>  better then any built-in sound-card.
> 
> Arnold
> 
Arnold,

you're right - the pcm2902 codec is broken by design. The internal voltage 
reference shows a terrible distortion because the 1 kHz usb clock isn't  
decoupled properly. The data sheet 
(http://focus.ti.com/lit/ds/symlink/pcm2902.pdf) recommends the use of an 
external voltage reference for "a high-performance application" (figure 37) - 
unfortunately Behringer uses the circuit for "a simple application" (like 
figure 39). 
I tested my UCA202 with Fons' jaaa and got a "nice" peak at 1 kHz - it went 
away after adding a REG103-A to my UCA (you can get free samples from TI).

Ciao Martin