Great unit, decent price. As some people have mentioned, i have the bad hum sound when tuberolling. I switched the big tube with the the NOS RCA 6AS7G and it works fine without distortion, but with the small tube, switching it causes the humming issues. Ive used a few Electronic Harmonix (6SN7 Gold) and Tung Sol (6SN7GTB) to no avail. I tried burning them in for a few days, but the hum persists. I will soon buy a few more (Sylvania or RCA) to see if i can find a decent one that doesn't hum as much. Otherwise, it sounds great, most of my amps were around the 100$ range (Schiit Vali, XDuoo TA01) and this Darkvoice is far richer in sound and range (at least to my ears). Tested on Senns 600 and Senns 650 with this unit. Would recommend this, but wary that tuberolling is a vortex of cash.
maheeSorry i didnt posted the result but no, the tung sol kept the hum after a few weeks trying. I bought an amperex NOS 6SN7 And it works quite well. So in total i have 2 electronic harmonix, 1 tung sol, 1 amperex and the default chinese tube. Only the Amperex and the default tube dont hum. Seems inneficient. Also, keep in mind the tung sol and electronic harmonix costs around 20-30$ , i bought the amperex for 70$. Im guessing the quality could ve be a factor here.