mhdt Orchid - hum noise

I'm waiting for feedback from the manufacturer. Unfortunately I'm in Europe so LTA may not be the best option but thanks for the suggestion, always good to have options.

I made this little clip:

it was playing well for an 1h and after I started noticing this hum once again. I turned off the music when I recorded the clip, actually even without any signal the hum is there. I even test it without any tube and the hum is there. As soon as I turn off the dac, it goes away, turning up and down to volume nob also increases / decreases the audible noise. 

:(

Did you disconnect the usb cable? I had the same sort of issue when my usb cable was connected. Let me know.  

thx for bringing more suggestions that may help me troubleshooting this issue. I'm not using USB, I mostly use RCA. Actually the USB cable wasn't even connected when I first noticed the issue. I have tried with USB and no difference. Actually, even without any sign sent to the dac or cable connected (appart from the audio out) I get the same issue. When I first turn it on, no issues at all, but after an hour, give or take, this hum starts.

By the way, one of the reasons I got this dac was also after reading some of your reviews and mods :) I actually waited for a few months to see if you were selling any moded orchid :) ... just a side note. Thx once again, I appreciate your message. I'm starting to think I can't escape to send the dac in for repair.