The Amp Garage

Hey Dan, Thanks. It sounds really awesome, only slight drawback is that the inactive channel needs to be at full volume for the active one to not be loaded down ( if it's at 0 the mixing resistors attenuate it by 6db and it sounds weak) but that's no big deal. The logo as well as the faceplates were...

Not sure if it's OK to hijack another thread like this, but since I already engaged here let me share my build too. It's a JM signature with the EF86 channel of the Matchless C-30 combined, for a friend who couldn't decide.

Thanks Dan for sharing this information, please let us know how your amp has improved after the changes

Thanks for your quick reply. So it is the reverb mixing resistor that needs switching it seems right? Or I am completely ignorant on how the mixing network works... Just to make it crystal clear for future builders as well, because the two schematics below, have the 68K resistor on different sides (...

Hello everybody, I also built an amp based on the JM, and it too seems to have somewhat anemic gain. The solution of swapping the mixing resistor to 220K seems like the first thing to try, but looking on all the discussion in this and another thread by Marcus i get some conflicting information. You ...

Hello again, Well, the resistors for the artificial center tap i had forgotten really made the whole difference. After installing them and switching to a 12ax7 as suggested the amp is perfect. Really low noise and absolutely beautiful sound, both in clean and overdrive!! Boy is it a singer... Many t...

Thank you very much martin for taking the time to help me. Are these two resistors supposed to be of high power rating or 0.5-1W? I will install them and change the PI tube in approximately two weeks and i will report on the progress here, for future reference.

The 12AU7 in the phase inverter will cause the lower plate voltages there. The 280-290V values are for a 12AX7 that draws only 1mA or so. The 12AU7 draws a lot more current and will drop the plate voltages. Why not use the standard 12AX7 there? Did you modify the component values around the phase i...

I guess it would help, but i won't have the amp in my hands for another two weeks, as i am traveling, and I was hoping to do some research on the matter during this time. So if someone has experienced something similar before, or has the technical knowledge to suggest some possible causes, that woul...

Hello, I recently finished a dumble clone build based on the Ceriatone overtone HRM 50 and this http://pdfelectronics.com/dumble-ods-100w-hrm/ build. I modified the design, and i have the HRM tonestack's pots (normal pots not trimmers) as well as the OD and PAB switches on the faceplate. I used hamm...