Thanks Dynaman! High gain build finished.

[Normster]

A couple of years ago, Chris posted a very cool photo of a high gain amp he had for sale. I've been obsessing over that amp ever since. I finally got off my lazy butt and built one using his layout. Came out pretty good and I'm sure my son is gonna love it.

Anyway, just wanted to say, "Thanks for the inspiration, Chris!"

[martin manning]

Really nice Normster! I see four inputs in the outside shot, only two in the gut shot? What circuit is it?

[passfan]

A lot of really good build technique in this shot. Kudo's to Normster and Dynaman. We can all learn something from their style and layout.
That is a fat and happy looking variac in the background there Normster. Looks like around 10 amps or so, eh ?

[Normster]

The amp only has two inputs. I'm using a Plexi faceplate but I'll plug the other two holes or put switches in them. The circuit is based on a Soldano Avenger schematic that been on Schematic Heaven for years. No clue how accurate it is but the amp works.

Yup, BIG variac. I wish I had something smaller, but MCS used to blow these out pretty cheap.

[Structo]

What?
No tool box?

Looks great Norm!

[Normster]

Big red Snap-on tool box is on the other side of the garage. (I was a mechanic for 20 years.)

I got a chance to play the amp some today. WAY too much gain for me. However, I put a 12AY7 in V1 and it makes a pretty nice blues amp. I'm sure my son is going to want the 12AX7 though.

[Reeltarded]

That sucker is very clean! Nice stuff Norm. Some of you guys are machines. So nice.

[Drumslinger]

Excellent build there Normster!

[fopoman]

sweetness!!

[dynaman]

Hoowee muskie, that looks sweet! Don't thank me, thank Mikey Soldano and those other OCD builders for stepping out of the box! Dang, I don't even see any "cheater" snubbing caps in there to keep the squeals away. Awesome!

Did the bias balance work out OK? How's yer hum level?

Gonna have to step up my gain, er, game now.

[Normster]

Thanks, guys.

Chris, the bias worked great once I found the right combination of resistors. With the 300-0-300 PT, 100k -> diode-> 15k -> 25k trimmer -> 10k balance -> 100k tails gave me enough range for 6L6s. Haven't tried EL34s yet but if I need more swing I can probably swap the 25k for a 50k. BTW, I found a "fail-proof bias" circuit that I may try next. Very similar to your circuit.

There's a little hum at HIGH volume, but not enough to justify DC heaters. Overall, I'm very satisfied with the noise level.

[dynaman]

Haha, that's where my screen name came from - Dynaco. I've owned dozens of Dynacos.

Meh, I've tried unregulated DC on the heaters and it was more trouble than it's worth. Regulated DC would prolly be better, but I haven't had many issues with good old AC. I'm sure others have used DC with more success than I've had.

You can also tame those 12AX7s with some switches to cut gain. Pull a cathode cap in and out, alter the values of the volume pots or bleed some signal off somewhere. That Avenger is awfully aggressive with 1M pots. Nothing wrong with using other tubes though. That's usually my first recommendation so you can always go back to 'AX7s.

Glad you got it running.

[M Fowler]

Which layout was Normster's amp based off of? Can you post it?

Mark

[Normster]

That's my current stereo system...Dynaco ST70 with a couple of "econo wave guide" speakers made from old gutted Pioneer 77s. Makes me smile every time I crank it up.

Mark, it wasn't a "layout" so much as a photo. I used the photo and the Avenger schematic and adapted things to line up with a Plexi faceplate.

Edit: Added jpg version of my layout. Adapt at will.

[M Fowler]

Thanks a lot Normster.