I am currently designing a tube amp that I want to realize with a PCB layout. I want the tube sockets, as well as all the components for the preamp and poweramp to be mounted on the PCB. I have done some experiments already and have a power stage that works like a champ with no layout problems; however the preamp is proving to be much more difficult. I am having lots of problems with the 12ax7 preamp tubes, mainly in that they break into free-running oscillations whenever I turn the preamp volume knob up past 6. Here are the design specs:
Amp is 1 channel with a mod switch:
-Lead mode: 3 grid-cathode biased gain stages, almost the same thing as a slightly hot-rodded jcm800
-High Gain mode: All the stuff from lead mode, plus two more grid-cathode biased gain stages
Nothing real special there
The phase splitter is basically straight out of a Marshall
So there really aren't any serious design quirks, but does anybody have any PCB layout tips? I know to keep grid stoppers as close to the pin on the tube socket as possible, what about cathode resistors, cathode bypass caps, grid leak resistors, coupling caps and plate resistors, any special considerations I should take there?
Also, any tips on grounding schemes for a PCB tube amp?
Any input would be greatly appreciated.
Amp is 1 channel with a mod switch:
-Lead mode: 3 grid-cathode biased gain stages, almost the same thing as a slightly hot-rodded jcm800
-High Gain mode: All the stuff from lead mode, plus two more grid-cathode biased gain stages
Nothing real special there
The phase splitter is basically straight out of a Marshall
So there really aren't any serious design quirks, but does anybody have any PCB layout tips? I know to keep grid stoppers as close to the pin on the tube socket as possible, what about cathode resistors, cathode bypass caps, grid leak resistors, coupling caps and plate resistors, any special considerations I should take there?
Also, any tips on grounding schemes for a PCB tube amp?
Any input would be greatly appreciated.
The putzophile solution.
Possibly ot but instead of circuit boards I use a kind of hybrid construction approach based on phenolic plastic and small copper tubes for parts designed to be used on pc cards.
Basically I drill the holes in the plastic where I need them and insert a short section of copper tube that makes a through “plated” hole. The wiring between parts is done on the bottom side of the board from hole to hole kind of like an old terminal board. The advantage is that it can be rewired easily if it doesn’t work the first time and for me at least, the retro look.
Possibly ot but instead of circuit boards I use a kind of hybrid construction approach based on phenolic plastic and small copper tubes for parts designed to be used on pc cards.
Basically I drill the holes in the plastic where I need them and insert a short section of copper tube that makes a through “plated” hole. The wiring between parts is done on the bottom side of the board from hole to hole kind of like an old terminal board. The advantage is that it can be rewired easily if it doesn’t work the first time and for me at least, the retro look.
I did think about doing it the putzophile way, but I really want this to work out on PCB, even if it takes a few tries. From the little bit I have gotten my current prototype to work it sounds pretty killer, and by using a PCB (since I think it is a bit complex for a turret board) it would be easily replicable. So, does anyone have any PCB layout tips/tricks to share?
Also, I am thinking about (if I ever get a working PCB) making it available as a kit and/or full amp for a reasonable price.
Also, I am thinking about (if I ever get a working PCB) making it available as a kit and/or full amp for a reasonable price.
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