[John Stone]

On 7/13/10 8:34 PM, in article
,
"Shhhh!!!! I'm Listening to Reason!" wrote:

I found most 6GH8s hummed in the ST-70 circuit I had which is my only
experience with them. That circuit was "phooey". I use Tele 6U8s in my
Scott, they do fine. I have about six more of them NOS.

I had a Dyna ST-70 that I dropped a new board into that used 6GH8s. I
never found one I liked. Amperex and all the other big names, bith US
and Euro, didn't work out very well.

Not sure why that would be, except that the 6GH8, like the 7199, was very
prone to heater to cathode leakage. I've used 6U8's in the Dyna circuits
with very good results. 6U8 and 6GH8 are very similar and can be directly
subbed for each other in some applications. The Sovtek 7199, which is now
discontinued, also had problems with hum in certain amps. You could fix it
by running the heaters on dc or superimposing a small amount of dc between
heater and ground.