[tvurce]

I am upgrading from Audiotrak Prodigy HD2 to Asus Xonar Essence STX. Prodigy HD2 is great soundcard, but only for PCI and it needs 12 W on 5VSB rail from PSU (and I am moving to new low-power PC with PSU only with 10 W 5VSB). But before that, I am testing both soundcards in my old PC, with Pioneer A-30 amp and Wharfedale 9.2 speakers. 
 
Sound from Essence is pretty good, but I hear some weird thing - sound "pumps" in strange way. It is very hard to hear, but it is like move volume up and down little bit and very fast. It is mostly hearable with brown noise test sound. 
 
I appreciate very much, if someone could test it for me on his STX. Here is that sound: http://www.audiocheck.net/testtones_brownnoise.php
 
On Prodigy, brown noise sound is pretty still and straigthwards, no pumping at all. 
 
Tried also some opamps swaps (LME49720), but problem on STX persists. 

 

[billybob_jcv]

You might be hearing your power supply. The Essence might not have as good a resistance to EMI or RF noise, or it might not be as good at regulating the power coming from the computer PSU. An external soundcard that is powered by a separate, regulated power supply might reduce the possibility of noise.

 

[cel4145]

You might also try the STX in a different slot if you have one. Could be its location relative to the PSU or GPU is causing the problem. Could be it wouldn't be a problem at all in your new build.

If you don't need the virtual surround features of the STX, nor the headphone amp output, get an ODAC.

 

[cel4145]

ODAC: http://epiphany-acoustics.co.uk/products-page/dacs/e-dac-24bit-miniature-usb-dac