Author Topic: Stuffed Fallstaff in a little box. (Non-madbean)  (Read 1910 times)


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  • Jon P
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    • Midway Fair
Stuffed Fallstaff in a little box. (Non-madbean)
« on: April 23, 2012, 08:55:33 PM »
My Tayda order didn't come on Saturday, so I couldn't finish my Lowrider or a couple Effdub builds that I was missing a couple ICs and random parts for. I did get all the cases painted and switches and jacks ready for the baby boards, so those should be ready within days of my order getting here (it just shipped today! can't wait).

Instead, I amused myself by building one of my Fallstaff ODs in a 1590a. (Here's the build report from the prototype, with the schematic and build PDF: I used 1/8watt resistors and 50v caps, and that's a 25v tantalum in the audio path. I regret not making the layout more square - I had to carve up the Neutrik output jack to get the board to settle far enough in the case that it didn't feel like I was squishing anything. (Though I could have turned the board around and flipped it upside down if I were willing to resolder the wires to the pots, which I wasn't.)

I wired the tone pot backwards so that it would say "less" this time, intending to do the same with the volume pot. Unfortunately, I forgot to actually do it when it came time to solder the wires to the board, so that one still says "more" ...

And the guts:

I did a couple fun and mojo things in this build, since there was no point in having two that sounded identical:
The Ge transistor in this one has a gain of 50hfe, and it's so leaky that when I was testing I didn't notice at first when I had it flipped it around backwards. (It still provided a good 6db of boost with the volume cranked.) The boost still gets pretty hot. I'm thinking of ordering some in the 40 or even 30 range from Smallbear just to see how low I can get them to work before they start to lose character.

The silicon transistor was an unopened RCA 2N2270 purchased in the 60s or 70s that I got from LucifersTrip's yardsale on DIYstompboxes. I got some really low gain 4JX11B1634B (all around 50-60hfe) that sounded great in both slots, too, and I considered just using two of them since a couple of them biased correctly in Q2. I got really lucky with the biasing on Q2 (7v exactly) since I basically was limited to the 1/8watt values I ordered for the Madbean builds, but I ended up with three different transistors that would have been within .1v of the magic number.

The orange and yellow diode is a 1N192 pulled from an old radio. I tested all the ones I had and this one was particularly squishy, dark, and compressed while I was breadboarding. The forward voltage was a whopping .2v! I'm actually thinking it might be faulty since all the others were a steady 2.4-2.6.

This build's got much less gain overall than my first one, a little more distortion (I used a smaller resistor between the diodes and ground) and a more extreme treble cut on the color knob.

I'll probably add pulldown resistors tomorrow, which I'll have to wire directly the switch.
« Last Edit: April 24, 2012, 06:34:14 AM by midwayfair »
Myself's music & things I make: My band: PCBs of my designs from: (Bearhug Comp & Cardinal Harmonic Trem); (Hamlet+ delay & Blue Warbler envelope vibe); Snow Day OD/Flabulanche: