KT88s

[Gingertube]

No experience with Git Amps but quite a bit with a pair of JADIS JA80 mono block HiFi Amps.
The JJ KT88 had highish grid currents which meant that they suffered bias run aways with the crappy JADIS circuit (very high value grid leaks on the KT88s).
The Genelex re-issues were MUCH better with regard to this (grid current). The Genelex also biased at a little lower grid voltage.
Check the grid leaks against the max value on the datasheet. That value applies to teh tubes opearting at full 42W dissipation. You can double that max value if you bias for less than 35W anode dissipation.
Cheers,
Ian

[soundmasterg]

As I said before, the EH KT90's manufactured in the 90's worked as well/better as the OEM Genelex KT88's.

I think you are thinking of the EI KT90's...those were the ones that had the good reputation and the stellar sound. The EH one came later and was just a knockoff to profit from the hype.

We had been using JJs, and like the way they sound, but seem to be getting a lot of premature failures. An amp being driven into distortion with 700+ plate volts is a tough environment for any tube, unfortunately...

Most of the people that I have heard about having trouble with JJ were not getting them from Eurotubes. They do a pretty good job weeding out the poor stuff and are local to me so I've seen their operation and met them. They're good guys and try hard to get customers good stuff. That said, I think JJ's quality has probably slipped in the last couple years and their larger octal tubes which is sad to see as their KT88 used to be the best by far. I haven't gotten any recent JJ stuff but the stuff I did have was fine.

Greg

[defaced]

I think vht/fryette uses shuguang kt88s and (i believe.....) operate under similar conditions as your amp.

I don't know about their other amps, but it's not like that in the Deliverance. The B+ is around 475. Depending on the revision of the amp, there is either a choke or a resistor before the screens, so screen voltage is about 5v lower.