The Amp Garage

Amazing build! Excuse my ignorance, but what are the 220k resistors off of the screen grids for?

I used RJ's Edcor part for for the PT. I didn't go out looking for the 1650N specifically but a friend sold me one he wasn't using for cheap. I wouldn't say the amp I made with it is particularly magical or mind blowing but it holds it's own nicely next to my bandmate's English-made 90's AC30. Every...

I used the 1650N on a Rocket build and it sounds pretty good.

Got mine yesterday. Just skimmed through and noticed tones of new information. Definitely a classic!

I'm no expert but what you have sounds like classic 'motorboating.'

Maybe decouple the first stage and the PI giving each it's own cap? Since my last post on this one I've tried all kinds of shielded cables and grid stoppers, a capacitor across the plates of the PI, and changing the PI to a long tailed pair. I changed the filtering to: capacitor-choke-capacitor(OT c...

The only thing left is to build another one on a different chassis using the Fender layout and see if it does the same thing. I have and old Magnavox PT in the basement salvage pile that should have about the right voltages. I'll have to see what I can come up with for an OT.

... no wonder people crash spaceships.

Or that time Mr T chopped down all of those acres of trees on the old Armour estate in Chicago.

http://articles.chicagotribune.com/1987 ... ric-places

Thanks Cliff, Everything is nice and tight, but I just double checked. This is a real head scratcher. Thanks to everyone for sticking with me this far and for all the ideas. The low frequency ghost notes happen at all volumes, not just when the amp is turned up. I'm thinking about converting the PI ...

Thanks RP, I was really hoping that would solve my oscillation/ghosting problem. I took out the 6.8k resistor and went through a bunch of different values with my decade box. Changes there definitely changed the sound of the amp but nothing helped with the low ghost notes. Last night I took the amp ...

Hi Tim, I'm going to try replacing those this afternoon. One is something like 267k and one is 272k not off by too much but maybe enough to make it unbalanced? Here is something I read about the paraphase PI on Merlin B's site: "The two triodes could also share a common cathode resistor. No bypass c...

Replaced the last Russian coupling cap. No luck.

Took it to a different outlet. Same problem. Clipped in a 20Hy choke between the first two filter caps. No effect. Spent a bunch of time with the Telecaster playing through it. Same problem above the 12th fret. When playing three notes at a time with the tone control at 9:00 it sounds like someone h...

Thanks guys. RP, the screen grid resistors were 430. I heard the difference immediately. I tried a bunch of different guitars and different speakers. I haven't yet tried a different electrical outlet, though I've never had any problems with the one in my practice room. I'll try that today. The scope...

Here are some pictures of where I'm at with this thing. Almost ready to throw in the towel and turn it into something else.