Andrekp wrote:Gain-wise, a "normal" 18watt is not all that gainy in a modern sense. Don't know how much your choice of tubes causes so much gain, but I suspect it should still act normally. If you are hitting distortion just about 1 on the dial, chances are something is wrong.
18Ws have lots of good old fashioned voltage gain though, which is why they distort so much.
And it usually gets pretty crazy with the extra gain of a pentode in the preamp. So this looks like pretty normal behavior to me.
GUITARmole wrote:You mean 220? The StarGeezers schematic has a 200 ohm resistor there now...
Whatever value will drop a few volts. But if he's using 6V6s, then there's no need to worry anyway.
bigbeck wrote: I think Geezer made a typo here. In another post he stated that his cathodes were 21.5V. His big voltage difference was between the two 6v6 control grids,pin 5.
Control grids have to be at 0 volts, whatever happens. If not, there's something seriously wrong, which needs to be fixed before anything else.
StarGeezers wrote:Big, not yet ... got a 12AU7 (old) I can plug that in and see the difference...got a 5751 too for somewhere in the middle ... we'll try them all... PI Cathode R is 820R....
So now you've got all that extra gain, why are you trying to throw it away?
Repeat after me 10 times, "Gain is good, gain is good, gain is...."
bigbeck wrote: Try 12at7,12ay7 and 12au7. With at being highest and au being lowest.
Like I just said..... and I always thought you were the kind of guy who liked to fire up the barbecue...
kyoungsteadt wrote:You have to understand that ZP wants your amp to sound wild...
You bet!
StarGeezers wrote: Think restoring the tail R back to 56K would tame that wild PI??? 22K now as ZP suggested...
You need the lower value tail resistor, so that the PI can provide enough signal voltage to drive the 6V6s, which have a lot lower internal gain than EL84s.
bigbeck wrote: Edit: a 12at7 might be perfect for you,but might as well try raising the tail resistor to see what happens. Clean up to 9:00 sounds good as long as it's loud enough at that setting.
Actually, if it's breaking up at 9:00 (I assume you mean 9 o'clock on the dial), then that's pretty much like you'd expect from a regular 18W. It should then get progressively dirtier from there.
I don't believe there would be a benefit in using a 12AT7, as AT7s will drive the power stage even harder due to their lower anode impedance. They also bias differently to AX7s. If you want to trim off a little more gain, you can reduce the power tubes' 470k grid reference resistors, say to 330k.
would indicate that the awesome gain I hear is from the PI, since the "other 6SJ7 amps' didn't have anywhere near the gain this beastie' has... I'll never be able to use all the gain this thing has ,for what I'm playing... Oldies...I may just change back to the 56K and see what happens ...I'll still try out some other tubes as I can find them..The TeleF 12ax7 did sound good on 1...
...I could have easily overpowered the entire band, drums included... 
