High amounts of THD over USB and Coax...

[PeteB]

The Asus U7 has a full-scale input/output of 1V RMS (I looked it up). It probably should not be used for your test without attenuation.

On the other hand, your DAC probably has a full scale output of 2~2.1V RMS (this you can probably find on the manufacturers web site). If you send the un-attenuated output of the DAC, to the Asus U7 input, at 0db it will probably clip, and this is what you are seeing.

In other words, you cannot send a 2V RMS signal directly to a 1V RMS input without clipping.

Inputs on PC sound cards are easy to overdrive (internal or external). 2V RMS is about 5.6V P-P. USB supply voltage is 5V, if that.

Easy to check, buy a 6~12 db inline attenuator from any shop selling electric guitars... (or make a voltage divider from two resistors )

Someone else will have to explain the Rune Audio settings, but I would say that they are not related to your test. I do not think you need to worry about your hardware, it all seems to be working correctly...

[robertzombie]

[rastus]

I have a Behringer U-CONTROL UCA202, not sure this would be suitable.

http://www.music-group.com/Categories/B ... 02/p/P0484

[robertzombie]

[robertzombie]

Anyone else want to give this test a go?

[rastus]

[tboooe]

Hi guys, I posted the findings on this thread to the raspberry pi forums and one of the moderators pointed me to this thread:



I am not entirely sure what it means but it sounds like there was a discussion about clipping and limiting this possibility with a patch?

Here is another thread on the Hifiberry forums talking about lowering the volume to avoid clipping:

[PeteB]

@tboooey: This actually concerns only audio cards using the PCM5122 DAC chip. It is related to some annoying issues with hardware (not software) volume control on my DAC+, and any other board with the same chip, and drivers for that chip. It is not directly related to this thread.

There IS a thread here about related issues. It is pinned at the top of this (Raspi) forum.

Just as an FYI, you may not get a good hearing from the Raspberry Pi Forum mods discussing audio issues, because they would prefer to avoid posts which touch on the quality of the native analog output on the Pi (or any other shortcomings related to audio)... however, annoying them can be entertaining, so if you are so inclined, go for it...

In the case of the hardware in this thread, there is no PCM5122 on the DIGI+.

[tboooe]

[PeteB]

@tboooe: If nobody does it b/f I do, I will get an oscope sometime next week and just measure the signal at the analog output.