High amounts of THD over USB and Coax...

[robertzombie]

[PeteB]

Some of the screen caps in the article I posted show similar errors, and discuss some of the possible causes. It is a little long, and you have to compare to what you are seeing pretty carefully, but most of the potential problems are described there. Once you get the test conditions right, I am sure you will get much better results.

[robertzombie]

[PeteB]

If you want someone with the same hardware to repeat your test, which DIGI+ adapter are you using (what manufacturer)?

[tboooe]

[rastus]

The following reads may be of use....

Tracking down noise sources on a Raspberry Pi
http://www.crazy-audio.com/2013/10/trac ... pberry-pi/

Sound quality of the Raspberry Pi B+
http://www.crazy-audio.com/2014/07/soun ... erry-pi-b/

Sound distortions and the Raspberry Pi - reasons and solutions (read the 'comments' too)
http://www.howtoeverything.net/linux/ra ... -solutions

[tboooe]

[rastus]

PeteB does have a point... a quick read through that link confirms much...

NwAvGuyJune 2, 2011 at 3:22 PM
"...this is a classic case of "you get what you pay for". For the price, RMAA, is a useful tool. But, beyond the suggestions in the article regarding how to get the most out of it, I'm not sure what to suggest that doesn't involve spending some serious money."
http://nwavguy.blogspot.com.au/2011/02/ ... -rmaa.html

And here...
http://nwavguy.blogspot.com.au/2011/02/ ... thods.html
Search:
"RMAA IS NOT AS GREAT AS PEOPLE THINK"
"BAD TESTING IS WORSE THAN NO TESTING"
"TEST CONDITIONS MAKE A HUGE DIFFERENCE"

I would disconnect everything you can before starting the test, then add devices one at a time and retest, and compare them results. Or...

Try disconnecting from the network (no Ethernet and/or no WiFi).
Use a USB flash drive instead of a HDD.
Try a battery pack for power.

PS: Sorry about the caps, ooops.

[robertzombie]

[robertzombie]