mhdt Orchid - hum noise

Hi This started this week, I have the dac for around 1 year and never noticed it before. Let me be clear that this is not negligible, it is loud and it only get worst as I increase the volume, as if a constant hum sound was being plaid. It doesn't matter if there is any sign/music being sent to the dac through any of the digital inputs (USB or toslink or RCA). As soon as I turn on the dac I hear the noise thought the speakers, if I turn down the volume the noise goes away. looking inside doesn't show any issues. I was wondering if it could be something in the tube connectors/solder or indeed in the power supply. :(

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. 

:(

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.