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New "P1"
#1
Man - haven't posted on here in years.

Obtained an old P1ish amp that I built about 10 years ago and decided to have a look inside. It was not a P1 per the current schematic, but it sounded pretty good. Let a guy borrow it to test it out and he liked it but wanted more low end. Wasn't planning on giving him this amp but perhaps building him something else.

I got the itch to play around with a bit and the first thing I did was try putting the tone stack in between the gain stages. I'd never done that on a two tube amp. I used "Fender" values and cut a little bass into the EL84 to keep it from muddin' up. The result was a VERY clean amp. It would hardly overdrive the EL84 and when it did, it wasn't great sounding. Tried it with a booster to see what it would sound like and it was awful. Definitely a step in the wrong direction. The clean sound was pretty good though - fat and twangy.

Then I had another idea - not really a novel one, but one I hadn't tried before with a single 12AX7/EL84 combo. I'll call it Vox-ish. Preamp is a reminiscent of a Top Boost channel and the so is the tone stack, although it's still a "Fender" stack, just with values to give it a profile similar to a top boost Vox. WOW - this little amp blew me away. Really jibed well with the EL84 and with the lossy tone stack between the second stage and the output, it didn't drive it too hard. It gets a nice crunch preamp overdrive and when you push the master up it adds in a touch of power amp bark. Clean tones are pretty good too. There's a lot of bass cut available in that TS config so it grinds well but you can make it nice and fat for a clean tone. Me likey.

So really all it is:

1M/33k -> 12AX7 biased warm (220k plate, 1.5k/22u cathode) -> 0.0022u/500k Gain -> 100k grid stopper -> 12AX7 biased neutral (100k plate, 1.5k/1u cathode) -> Fender TS w/ Vox TB values (not hard to figure out basically the same thing with a mid control) -> 500K master -> 10k gs -> EL84 into 5k running about 300V on the plate and 290 on the screen.

Not sure everyone would love it but with Strat it friggin' rips. Open cords sound awesome.

Didn't try it with a pedal but I'd think it would be great - should verify but I doubt I'll change it anyway.
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#2
Here's some short sound bites.

https://soundcloud.com/mike-k-674473829/dr0000_0031mp3

https://soundcloud.com/mike-k-674473829/dr0000_0028mp3

Dropped the voltages just a tad in PSU to get a sweeter spot for the EL84 and also added a IRF820 cathode follower to boost the signal to the power amp a bit.

It's got a great clean tone too, but not much volume before it starts breaking up.
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#3
https://docs.google.com/presentation/d/1...sp=sharing
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