The Hundred-Buck Amp Challenge

[scott17]

Here are the guts of the little 6AF11 amp.

[djgibson51]

Here are the guts of the little 6AF11 amp.

Neat, compact, cool

Cheers, JimG

[kevinkr]

Originally Posted by scitizen17

Here are the guts of the little 6AF11 amp.

Very compact!

Nice job...

[Printer2]

Personally I hate doing ship-in-a-bottle builds. But whenever I have lots of space I get ideas of adding features and the space just disappears. That being said, I see room enough in their for a reverb loop (hint, hint). Just kidding.

[tubelab.com]

I used a compactron in an amp once and found it would be on the verge of squealing at full gain.....It took a quite a few iterations to eliminate the squealing oscillation but I finally got it out of there.

I have waffled back and forth on the compactron amp idea. I started one on perf board with sky wired parts and clip leads. It was a good multi frequency radio and TV jammer so thats where it stopped. I may revisit it if there is time but it doesn't look good. There are 3 pin comaptible tubes that fit. The 6AF11, the 6AS11, and the 6BD11. They are all in good supply and two are on the dollar menu.

My design uses two tubes. The high Mu triodes are the preamp stages the medium Mu triodes are the PI and the pentodes are P-P output. I get about 10 watts out of it cranked. No distortion numbers or clean power readings were taken since I never tamed it. I started a PC board layout but came to realize that trying to use two tubes with the signal going back and forth between them isn't a good idea. The layout could not be optimized.

Made PC boards for two new experiments last night. One is a 4 tube version of Amp 1.0 and the other is just a preamp with 2 tubes and a "distortion maximizer" circuit. Haven't had time to cut and drill them yet.

[Printer2]

Used the 6T10, dual pentode. The signal pentode is dual control, played with the voltage on it but it did not change things too much. Did it point to point, might have better luck putting it on a board. Ultimately it was the lack of power that made me put it aside.

[scott17]

Originally Posted by Printer2

Personally I hate doing ship-in-a-bottle builds. But whenever I have lots of space I get ideas of adding features and the space just disappears. That being said, I see room enough in their for a reverb loop (hint, hint). Just kidding.

I really like it for the compact size but it was difficult to wire. I had the circuit jumper-clipped together on the bench and had it working, but low and behold when I mounted everything in the chassis, there was that pesky oscillation again. Stupid wiring mistake on my part.

Reverb loop? In there? HA! Luckily I have have an external digital reverb.

[Cassiel]

I really like it for the compact size

Then you gotta love this one. I have a soft spot for small and cute things but....damn, I'm beginning to think I bought too small a chassis. LOL. That OPT (believe it or not) was the partner of an ECL86 output tube (vintage reel to reel tape recorder).

[Trout]

Originally Posted by Cassiel

Then you gotta love this one. I have a soft spot for small and cute things but....damn, I'm beginning to think I bought too small a chassis. LOL. That OPT (believe it or not) was the partner of an ECL86 output tube (vintage reel to reel tape recorder).

That's what she said j/k

Is that a pedal box? I think I have a couple about that size setting here. I always planned on doing one of those 6021 sub-micro amps but never got around to it.

[Cassiel]

Yeah, that's for a pedal box.

That's what she said

Yeah, that's what she said. So I built this as a gift for our first year anniversary.