Motherboard optical output is distorted at high windows volumes

Nabalazs · June 29, 2020

I have recently bought a DAC+Headphone amp. It's the FX Audio DAC-X6. It was cheap on Drop, thought it would be a good entry level DAC for me. But it seems to be having a problem. Connecting it to my computer via an optical cable, the headphone amp distorts. No matter the volume level. If I turn windows's volume down specifically, but turn the DAC up, the distortion is gone. The RCA outputs are not affected.

What is faulty here? I've googled around, reinstalled, uninstalled the Realtek drivers, disabled dolby enhancments, but nothing. I feel kind of bad having to turn windows's volume down, to get an enjoyable headphone experience. And no, I can not use USB, as I am using the USB input for my nintendo switch. The main reason I got a DAC in the first place. My monitor speakers dont do justice to the switch's games' sound.

Oh and if it means anything, I'm using a DT770 PRO 80ohm.

Have I gotten a faulty dac? Is realtek to be blamed?

Nabalazs · June 29, 2020

Update: Literally minutes after I made this post, I made a baffling discovery. TLDR: the fault is the DAC.

So all along, I had the DAC's RCA outputs connected to my speaker amp. An SMSL SA300. But I had it turned off, as I have no reason to have it running if I only want headphones. Well, I dont know how and why, but turning the amp on fixes the headphone output of the DAC. I assume there is some foolery going around with resistances. I dont know. So I guess PSA, if you buy the DAC X6, with the intent of also connecting the back RCAs to something, make sure you can keep the other device powered too, else the DAC distorts the headphone sound. And upon further testing, this issue affects the USB input too. The price of a cheap DAC. It's has quirks.