Tube Amp Archive

Ok, here's the PCB design I've done for the power supply board.

One other thing I thought of: Most octal power tubes like KT88 and 6L6 have Grid 3 internally connected to the Cathode. But the EL34 does not, so you need to make sure pin 1 and pin 8 are connected. Noticed that on the tube datasheets, so yes I've connected pins 1 & 8. Okay, you had the variable bi...

The only problem I see is that you might want to do the math for your bias. Couldn't agree more, sadly, my math sucks. After some testing it seems that the "sweet spot" I found was when R9 equaled about 670ohm. I have two 5watt resistors in series equaling 650 and am planning to order a few 680 one...

Yep, working on making things cleaner. Here's the layout of the PCB I made for the main board. One labeled, one not 300dpi for printing.

(edit)
Forgot to mention, I added the second gain control back in. I'm finding that I like that extra layer of adjustment even with the rhythm/lead switch.

Ok, found what I believe to have been the trouble. C11 was not actually connected to R16. Seems to me this would greatly effect the output of the 3rd stage. It's connected now, output is good, nice and high with both switch positions. Now the problem is crazy crazy feedback if I crank either the gai...

Ok, tested the connections on the socket, not missed wired or swapped. I also switched around the tubes to see if one was bad, nope, same effect. I'm stumped.

Righto! So, I replaced C6 and removed the pot on R9, replacing it with a 430ohm resistor for a grand value of 651ohm. I removed my terrible tone circuit and wired directly to main volume. Plugged in, turned on and so much better without that tone stack, rhythm still sounded great, but now lead was a...

Ok, photos it is. Be warned this amp is currently not pretty, I slapped it together on a board just to test it's working. It's a serious rat nest and yes, hums like mad. No worries, I'm re-cutting the board and putting it on a proper chassis next. I used a EL34 for the power stage (I had one around ...

Hey folks, sorry if this is a non-sequitur but I just hours ago finished my very first AX84-SEL, and I used xtian's layout. I LOVE this layout, having the power supply and the tone circuit separate from the main board is wonderful. I have one main problem though. My Rhythm/Lead switch is only giving...