High amounts of THD over USB and Coax...

[robertzombie]

I used RightMark Audio Analyzer to test the output of the Pi 3 (via my Rega DAC) vs the output over the laptop. Dynamic range is good, with the Pi offering an additional 1 bit of resolution over the laptop out. I'm confused by the high amounts of THD and IMD though. This occurs when using the Pi's USB out and my Digi+ coaxial out. It doesn't occur with the Pi's analog out however. I have tested every "sound signature" and they all produce the same distortion figures. Could someone kindly replicate the test with their DAC and see what the results say?

From left to right: My soundcard, my laptop USB out to DAC, Pi USB out to DAC, Digi+ coax to DAC, Pi analog out.

[silvrr]

What power supply are you using?

Are you connected to the internet via the Ethernet port or Wifi?

Finally what else is on the USB bus? Anything with a high power draw?

I'm not set up to perform the measurements but I know the above are a few things that users have attributed to changing the sound.

[robertzombie]

[silvrr]

Would be interesting if you can take some measurements without the Ethernet connected.

Does your USB hard drive have its own power supply or is it running off the power from the Pi USB connection?

[robertzombie]

[PeteB]

Hi Robert,

And welcome to the forum,

RMAA can be difficult to use without some other equipment to check and adjust the settings. Possibly that is what you are seeing in the results. Did you happen to come across this article about RMAA:



If not, scroll down to "RMAA Problems" and it may give you some direction on how to correct the settings for your specific case. It may be something as simple as volume.

Pete

[tboooe]

[robertzombie]

[robertzombie]

[tboooe]