Alva Goldbooks Tiny Amp.

    Valco/Supro inspired build

Finished my latest build a couple weeks ago, and I figured I'd post a few thoughts on it.

I wanted to challenge myself and build a tube amp into the smallest enclosure that I could. The enclosure was only 7 inches wide, 2 inches high and 3.5 inches deep. Smaller than those old Russian Big Muffs. Our own Carey Gruszie made the chassis for me. Thank you, Carey!

I used an Edcore XPWR 024 power transformer, but removed the upright mounting bracket so it could be laid down on the chassis. I used rubber washers to isolate the screws from the chassis ground. This seems to work pretty well, but I wouldn't recommend going through the fuss to others.

Output transformer was a 5w Classic Tone SE, and I used a JJ 12ax7 that Chris Hurley sent me and a 6005 power tube (mil-spec 6AQ5) that Denny Allen sent me.

Part of the goal of this amp was to use as many of the spare parts I had laying around the garage as possible, the jacks and power switch was Chris's and the indicator light was a 120v neon I had stashed for a while that I got from RadiosShack.

I used Jupiter coupling and tone stack caps on this just to see how they'd sound. I like them, but not sure they're worth the price. All resistors were metal film or wire wound. I used a pretty large 5W wire wound to bias the power tube since I just had it laying around.

The EQ was the fun part of this circuit. It's the Big Muff circuit originally found on a Supro amp. it's particularly picky about it's source impedance, but I found that by changing the values of the components, it works reasonably well. The curves were designed to mimic a Fender blackface amp with all the controls set to noon. Pushed to 2 o'clock it sounds very British, at 10 o'clock it sounds bluesy, but all the settings are very musical sound and very usable. I like it a lot, despite the high loss of the stack itself. These losses cut the overall volume of the amp considerably, and would have probably benefited from another gain stage if I had room for it on this amp.

Here is a schematic, but the bias resistor isn't correct, I used a 470 ohm.     Alva Goldbook.

 

Schematic

Amp insides.

Component Board.

Amp picture.

Tone control Response.

Alva's Big Muff control in green. Fender Black Face in Blue.

Tone control Response.

Big Muff control in the Tiny Amp. Pot at noon, CW, and CCW.

Tone control Response.

Fender Black Face.

Sound clip.   https://www.youtube.com/watch?v=E3eHQjvoMH8

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