I have had my DV several months now, I love it. I have the 336SE. I had no noise issues with the stock tubes.
I use mine in a different way, as a headphone amp for my electric guitar rig, it’s mind blowing.
After a few days the pilot LED would flicker on and off and quit working altogether but, the amp worked fine. Then the right channel started cutting out intermittently and could bevrestored by tapping on the volume knob (of which by the way I have replaced with a vintage Bakelite and aluminum knob).
I finally got around to repairing my solder station and broke into the Darkvoice (literally, I had to break anti-tamper seals on 2 of the screws). What a nice looking build.
Upon inspecting the LED pilot light circuit I reflowed some questionable solders and the volume pot too… Problem’s repaired… 2 weeks now and no more issues.
By the way, I have mine on a dedicated power strip along with a small fan (blowing on the DV) and use the circuit breaker on the power strip to turn my “system” on and off.
After watching tons of youtube videos I decoded to try some different tubes. First, I tried a JJ 6sn7, it sounded nicer then the stock tube but was too noisy, so I put the stock tube back and scored a NOS GE 6AS7 power tube… big improvement. And lastly, (on ebay) I got a “test NOS” 6SN7 for cheap… mind blowing.