I've continued to enjoy this amp a ton. A week or so ago the amp blew a fuse, then another, then another the next day. Instead of remaining rational and searching for a reason, including the tubes themselves, I emailed the seller. I will give them credit, because the unit was beyond the amazon return window, but the seller agreed to refund my money once I returned the unit. Gemtune/Nobsound/Gold Dust is very responsive as it turns out.
Because of the hassles associated with shipping, I decided to do some googling and found the problem in short order. When I first received the unit I had replaced the rectifier with a JJ 5AR4, and the preamp tube with a Sovtek SL67. Well, I never saw a flash in the rectifier but it must have gone south on me, which apparently is common with JJ rectifiers early in their lives. Once I installed the original tube set, the unit worked like a champ and has continued to do so ever since. I guess I'll order a Tung Sol or Sovtek rectifier to have on hand.
So, now I have a little baby APPJ miniwatt on the way from MassDrop, which will go on the desk where the Gemtune is now. The Gemtune has much more power than I need for desktop Klipsch R-15Ms, so I'll find another spot for it. 8 watts per side is overkill in my offie system! Go figure. It's a good problem to have, to have an extra tube amp on hand. I have a set of OBs in the basement so maybe I'll find a way to drive two of the OB drivers with the Gemtune and figure out the other half of the equation from there.
Anyway, sorry to reawaken this thread, but the Nobsound/Gemtune 8W EL34 units are really great in the right applications.