The Amp Garage

I have had a very similar situation in a cathode biased 6V6 amp just this week. A harsh brrrraapp noise but only at higher volumes when the driving signal was larger. A first I thought it was a broken speaker because that's what it reminded me of, but swapping that proved it wasn't. Then I changed p...

Why not put in a On/None/On switch and wire in your cathode resistors in parallel to the switch, that gives you three values to choose from. Then you can run 2 or 4 6V6's or whatever you want. I've done that on many amps. I also like the lower voltage on the cathode biased amps. You can use switch o...

I love those "clean with hair" tones where soft playing is Fender clean, but hit it a little hard and you get some grit. An EL34-based power amp just seems to have a more natural clean to distortion playing curve. LeftyStrat, what negative feedback are you using if any? It seems to me that amps wit...

Yes the DC30 has the center tap lifted for the standby. I think there was a 2KV cap there as well around the switch. DR Z does the same thing on the Z-28. I'm not sure of the benefit of this versus just interupting the HT. Note:If you ever use the transformer shunt method to check bias, when you tur...

Do it! Chase the tone. It's an experience worth having. I've made made (2) Expresses and (2) Derailments (SE-TW), didn't like any of them and tore them into something else (Marshall), and yet I learned tons of tweaking tricks along the way. I figure the more I try, the more I learn about the process...

Yeah, that's it, I think there is a similar circuit in the Torres and TOT books for cathode to fixed bias switching. I have that switching option in my Bogner XTC and I have also put it in my own amp design at the customers request. I find that personally I like the cathode bias on EL34 more than fi...

I guess I don't see what the fuss about the Ghia is. Owned one, sold it. Friend has one, I don't ever ask to play it and he rarely does. It has one basic sound and although I admit it's a good one especially through a 1x12 Celestion Blue, I found it too limiting for the variety of music I need to pl...

For loudness in small amps, don't forget about what voltage dividers and negative feedback can do. Adding negative feedback can make a loud amp not loud any more. The AC 30 is much quieter if negative feedback is added and well it doesn't sound like an AC30 anymore either, but thats another story......

I'll check Mercury Mag spec sheet, but they are big, like 4 lbs. I was using them for the High-Octane schematic. The one with three gain stages and a single EL-34. They have 4,8,and 16-ohm taps. Axiom OT SE-3K Single ended -- 4, 8 & 16Ω taps Here's what Paul from MM said "The Axiom SE-3K outpu...

I'll probably bring three builds. A single ended head that's best described as what Jim Marshall would have made if he had copied Fender's Champ instead of the Bassman, a 5881 version of my high gain head, and my favorite high gain head which is a melding of Mashall and Bogner ideas into a low volta...

Any builders in Seattle going the Guitar show in Kent, WA this weekend 9/23. http://www.seatacguitarshow.com/default.php I'm sharing a booth with my friend who sells a lot of used PRS guitars, pre-'91 stuff usually. I'm going to bring a couple home builds and maybe some extra parts. If you want to t...

What I build into my amps is two master volumes that are footswitchable with a DC powered relay DTPT switch. I think they are the 5VDC Ormrons. I also have switchable gain controls using the same relays. That gives me four combinations. High gain/low gain and high vol/low volume or any combination. ...

OK I checked all the voltages and in short (no pun) nothing seems out of the ordinary. Other than the somewhat low voltage that is. I'm not sure why I had measured only 367 before. I did change some pre-amp tubes back and forth. B+1 381 B+2 365 B+3 290 B+4 274 B+5 258 Bias -30 screen current is 6 mA...

I'm in the finishing stage of my express build and but I only have 367 VDC on the plates. I saw an earlier thread where someone had the same issue. But the thread does not go into any details about how it was solved. Does anyone have any ideas/solution on how to get the ~400 VDC I should have :?: Da...

I completely agree, a single EF-86 is not enough gain to drive a PT. I've also tried one EF-86 with PI into a push-pull EL-84 sections, not enough. My latest version is an EF-86 cascading into a paralleled 12AX7 section, then PI, EL-84 push-pull power. Almost as much gain as three 12AX7 stages. Plus...