clipping issue DAC/driver

[astroreflux]

I need some insight on this. Im using an SDAC and a Schiit Modi 3. when i use usb input on either of them and crank spotify or foobar to 100% i get clipping (observed through peace gui for eqAPO.) though when i use optical through the modi its fine. this is independent of windows volume (which would make sense cause the apps are running in exclusive mode). Except when i disable exclusive mode its the same... - would this suggest eqAPO is doing something even with all processing turned off? but then why is it an issue only with usb and not optical?

i dont get why using USB is creating the problem. the optical out is using realtek drivers so maybe that is limiting signal to the modi and therefore preventing clipping, but as far as i know i cant bypass realtek and still use optical to test this theory. so then why wouldnt windows do this for usb signal? maybe cause sdac and modi use their own usb drivers? but then why wouldnt shared mode fix this?

cant seem to TS it myself. ive tried swapping usb cables, ports, using shared mode on both devices - which apparently doesnt work judging by the fact that windows volume doesnt effect it, though does change the actual output volume to the device. which means there is distortion before windows applies volume, which means the problem is happening somewhere between the music app and eqAPO, but not either of those programs themselves as the issue does not exist when using optical/realtek drivers. if it is realtek, that would mean the driver is doing something between the app and eqAPO, and then windows is controlling the output to the modi. this is really confusing.

obviously i could just turn the app volumes down, or pre amp down in eq automatically to reduce clipping just enough without reducing dynamic range. but it feels like a dirty approach.

 

[Wayne A. Pflughaupt]

QUOTE="astroreflux, post: 200730, member: 7728"]
obviously i could just turn the app volumes down, or pre amp down in eq automatically to reduce clipping just enough without reducing dynamic range. but it feels like a dirty approach.[/QUOTE]

Well no, it’s actually the right thing to do.

Don’t know exactly how this plays with your setup, but coax and USB are different protocols. Coax is for digital audio signals (PCM, DD bitstream), while USB is for data transfer.

With digital audio, the standard for signals passing from one component to another is less than 0dBFS.

I’m no expert in USB and data, but I expect there is no standard from one platform or app to the next.

Hopefully someone better qualified will comment further – I’m surprised Amir hasn’t weighed in.

Bottom line, there is absolutely nothing wrong with adjusting levels to avoid clipping.

Regards,
Wayne A. Pflughaupt

 

[Blumlein 88]

Well obviously turning it down or not isn't really the OP's question. He is wondering why this happens. It shouldn't. So what is the difference in USB vs not USB? The most likely culprit would seem to be eqAPO from the description in the OP. I did read that the way this software is implemented it causes a frequency response ripple even when set flat. That would be the reason right there if this is true for clipping. I don't have the software so can't confirm that is now eqAPO works. It would not explain why USB and SPDIF inputs differ.

 

[astroreflux]

Don’t know exactly how this plays with your setup, but coax and USB are different protocols. Coax is for digital audio signals (PCM, DD bitstream), while USB is for data transfer.

Regards,
Wayne A. Pflughaupt

so the data is "packaged" differently over each medium? that wouldnt really explain why there would be a difference in the levels read within eqAPO, as it looks like this is happening before anything is sent to be decoded by the DAC. if i open eqAPO and play a song, i can observe the changes by switching the default audio device within 'playback devices'. there is still occasional clipping through coax, but through usb its constant. if i switch on the automatic limiter and leave it for about 10min, the limiter might set about -3 on the coax device and -10 on the usb.

I did read that the way this software is implemented it causes a frequency response ripple even when set flat.

yeah i have it set flat, everything off. i cant find any info about eqAPO adding distortion on its own.