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Any PNP Ge should work. Select R24 as req'd. Mind the pinout. GT309 has the emitter on the middle pin.

Looks good, but I do not recommend 2N3904 & 2N3906. This circuit needs high gain transistors. NPN: 2N5210, 2N5088, 2N5089, BC549C (reverse pinout) PNP: 2N5087, BC560C (reverse pinout)

We'd need to tweak a few caps for bass.

VERIFIED! Component Side: minor update - I swapped C21 & C22 and made R11 longer Solder Side:

C5 only connects to GND & R8. No connection to U1-6. One last iteration: C13 added. The AGC loop had a bit of ringing and overshoot. I'm just finishing a Vero layout.

Any time you build a JFET circuit without selecting JFETs and/or checking the bias, you are rolling the dice. My mods are not more sensitive to JFET selection. It is I who is sensitive to JFET selection.

Air circuits!

I don't know, maybe. Haven't tried it. The thing I like about this circuit is its fast attack. Increasing R21 reduces the compression, so that might be a better place to start. I ran some sims and they show that R9 has very little influence on the attack speed because Q1 and Q3 have a lot of...

Just follow opamp best practices. Keep the traces connecting to U1-2 and U1-6 very short. Use a ground plane. Position C21 near U1 & U2. Make sure you have the most recent schematic, I had to update it again just now.

I just updated the schematic. I improved the loop compensation, deleted one capacitor, fixed a typo and corrected the duplicate ref des.

Here's the final version. No charge pump. Much better EQ. The Black Finger cuts a lot of the treble when SUSTAIN is turned up. This version maintains the treble content at all SUSTAIN settings. A very transparent compressor. Can handle over 1Vp-p input without saturating.

Here's the C3-PO parametric filter. Top view: 16 cuts 8 links, 4 on the bottom. For the bottom links, just bend over a lead to join 2 adjacent strips on the solder side. For example, the purple GND strips on the left.

This Vero layout is for the R2-D2 Opto-Face. Yeah, it is some Crazy Shit. Top View: 10 cuts 4 links - 2 on the top, two on the bottom. Bend D1-A over to join the two GND strips and bend the right-hand lead of R3 or R4 over to join the two pink power rail strips.

Where can I find a schematic and/or description of the Pumpkin Patch mod?

I'm working on a no-charge-pump version. It's looking good so far. Just a couple more tweaks...

The LM13700 datasheet explains the linearizing diodes pretty well, so I won't repeat it here. I chose the LM13700 because I was trying to keep the design as close to the original Black Finger as possible. The LM13700 does the job well enough and costs less. The SSI2164 is a very good quad...

And I'll wager they still work.

Bear in mind that the Mojo Maestro's performance will vary depending on the output level and impedance of the device driving it. An extreme example would be direct driving it from a guitar. Most guitars will not make a strong enough signal to drive the diodes into conduction and the Mojo mode...

xxx201, 2N5457, 2N5952 and xxx4393 will all have gain and require different biasing. xxx201 will have the least amount of headroom and I expect it to get pretty nasty when GAIN & BASS are dimed. One could use different part #s for all 3 trannies.

It's harder to find a quiet Ge trans than a quiet Si trans. A low-leakage Ge trans is needed in the Rooster for low noise. The Beano Rangemaster has fixed bias and a HEAT knob to control the gain. The Rooster always runs at max gain. Those two factors cause the Rooster to be noisier. I ran...