The Amp Garage

I must be missing something - not for the first time. The screen to cathode cap blocks DC from getting from the screen to the cathode, and it's rated to deal with screen DC voltage. The cathode bypass cap is rated to deal with the DC voltage at the cathode. I'm guessing you could just send the scree...

The Hybrid A into 6V6s would probably be perfect for you. There's a speaker recommendation thread here somewhere. I think Bob I built a 6V6 amp - look for his posts for tweaks.

I'm waiting on parts for a 4x6V6 tweed Bassman build, and I'm thinking of using the general Wreck style tube and transformer layout. I was just wondering if anyone else has built an amp like that.

I think if you do the math, a 10W resistor will be fine. But then it won't be "a la Ken" as they say in France. I'm sure I've seen this discussed here before.

Mark and Ron, thanks so much. So, being as my amp mostly just squeals with certain preamp tubes, and only when the preamp gain is MAXED, then I don't have a NFB issue, correct? Plus, my amp is basically an AC30 circuit, and that doesn't use NFB, right? Then, I most likely have an issue with some wi...

The NFB squeal is a screaming thing - you know it when you hear it. If your oscillation only occurs as you turn your amp up, then that's not your problem. Take a look at this Cornform chassis. Parallel wires all over, and evidently no problems. Just goes to show that it's not paralleling wires that'...

When I changed over from EF86 to 5879 I built a new board, and that took care of it. It might show up at full volume, but I never get it up that high. The usual suspects are grid wires - they're high impedance, so they're very sensitive. You want to keep higher signal wires away from each grid wire ...

I was thinking that the layout may be causing the oscillation when the gain is pushed a little higher. Even a low gain amp will oscillate when the right wires get too close together. Your build looks great, but there could be some position issues somewhere. I have a 2xEL84 amp with a pentode preamp ...

The "bogey" value for gain - 100 for the 12AX7 - is a target figure for that model tube. Depending on mfg. quality and testing, you may get quite a different value. It could be that your circuit puts 12AX7s at the edge - if you happen to get an extra-gainy tube, the amp starts to complain. You might...

I assume it's the 18watt site

If you get crackle through the speaker, then you know that the output section is capable of generating or passing signal. I'd start at the power tubes, and pull on every wire and component connection to make sure they are soldered solidly in place. I've had bad solder joints that had the end of the ...

ax84.com is a great site, and the P1 is a great first amp build. Many have been built, so you'll have a lot of help there.

I use a hammer and a metal plumb bob I found at Sears, but a center punch would do the job - anything metal with a conical shape. The eyelet should be just a little taller than the board is thick. I use 1/8" board. I got 1/8" eyelets once, so I countersunk the back of the board enough to let the eye...

Bob-I wrote:

rutledj wrote:Ok. What is PAB?
Forgive the noob questions

Yes, we have lots of new terms to use.

Pre Amp Boost. It's a switch that disables the tone controls for more gain.

Not to be confused with PBR...

Thanks for the review. Paul has done a lot for us beginner DIYers with his posts and his site. Great guy.

Now I have to build my Wreck.