I’m on a DIY mission to build a 200w mono guitar power amp, and stubbled across a PCB I like that I also want to make changes to. What I want to do is change the tubes from EL34s to KT88s, but am unsure of how to accomplish this. What will I need to change on the PCB, if anything? Will it just need to be rebiased, or will I have to add or take away different components from the PCB, and its power supply? I’m pretty new to this stuff if you haven’t noticed and am also having a tech help me build it so I won’t die.
Compare pin-outs of the two tube types. What is different?
More to the point: dropping KT88s in a EL34 plan will not change the power output enough to matter. Do you have revised operating conditions and transformers to suit?
Some people feel that PCBs are poor ideas in BIG HOT guitar amps. There is a cottage industry in ripping-out PCBs and installing turret boards. More robust and much more modifiable.
More to the point: dropping KT88s in a EL34 plan will not change the power output enough to matter. Do you have revised operating conditions and transformers to suit?
Some people feel that PCBs are poor ideas in BIG HOT guitar amps. There is a cottage industry in ripping-out PCBs and installing turret boards. More robust and much more modifiable.
KT88's need much more input drive signal than do EL34s's. You'd need to add or modify your driver stage to handle that.
> KT88's need much more input drive signal than do EL34
At similar G2 voltage: Not that much different. See Ampeg V40 rev.D which shipped with EL34 but a note on the chassis suggested 6550 (US KT88) for "professional" use. (Like inkjet printers today, the EL34 were "starter tubes".)
But if plate and screen voltages are raised to justify the fatter tube, obviously G1 voltage needs rise, yes.
At similar G2 voltage: Not that much different. See Ampeg V40 rev.D which shipped with EL34 but a note on the chassis suggested 6550 (US KT88) for "professional" use. (Like inkjet printers today, the EL34 were "starter tubes".)
But if plate and screen voltages are raised to justify the fatter tube, obviously G1 voltage needs rise, yes.