2020 Monkeymatic Lassen #4 (1482)

[ChopSauce]

I really enjoy your creativity...

[sluckey]

Very tidy. I like it.

[pompeiisneaks]

Very cool!

amazing how streamlined you can make it look with a few changes to the norm.

~Phil

[turbofeedus]

Very cool!
Is this the first project with the socket PCBs? What do you think of them?

[xtian]

Very cool!
Is this the first project with the socket PCBs? What do you think of them?

I'm thrilled. Made wiring much, much easier.

[xtian]

I started it up, but ran into some weird blocking on V2a. The kind where there's no signal until the grid is probed, then signal pops up. Something funky about my volume/tone controls. Anyway, made me rethink the dual-ganged pot approach, and now I'm going for something simpler:

Screen Shot 2020-11-07 at 11.13.35 AM.png

[pdf64]

Might it have been oscillating? If you were keeping the dual stuff, I'd suggest moving those 330k mixers to the tube socket / pcb.

[pompeiisneaks]

The one time I ran into that problem was that I had missed a ground. Using the DMM even though it was a high impedance path, gave it ground which started the tube conducting and kept it going, for some time anyway. I think in my case it was the PI ground had accidentally been omitted.

~Phil

[xtian]

Now we're happy! Simple is more good. Tone seems nicely balanced, not too bright or too dark. Put a 15w L-pad attenuator on output and cranked it up. Distortion is EXCELLENT. No fizz, no funny cut off, just nice and smooth and mean.

The voltages are pretty low and conservative: 310 plates, 11.5 cathode. I'll mark up all the voltages on the schematic later (schematic updated in post #1). That's only 80 dissipation, and I see a little x-over distortion, but it's making 12 watts clean. I'll decide if the x-over is bothersome when I can play loud.

[xtian]

IMG_4623.jpg

[xtian]

Here's an updated schematic with voltages.

monkeymatic_lassen_#4.png

[statorvane]

Very cool projects! Very nice builds.

[ViperDoc]

Any chance of an audio clip? Asking for a friend...

[studiodunn]

Very cool little amp!

[xtian]

Faceplate arrived.

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