Sewing Discord; Tonebender Mk. III

[acoustic olive]

A while ago on Reddit, someone posted a shin-ei companion fuzz housed in a gutted sewing machine pedal. I thought it was pretty resourceful (not to mention downright cool lookin'!), so I prowled Ebay for a few weeks, seeing if I could obtain one for cheap.

The hunt had coincided with my first foray into the Tonebender variants, and after settling on the Mk. III as my favorite, I refined my search to footpedals that could accommodate 3 top-mounted knobs.

I ended up ordering a Mecury model 229 for the enclosure. It wasnt too difficult to gut the carbon pile innards, but I found a few things meddlesome, namely dealing with the riveted treadle while tightening the footswitch and LED bezel. But all's well that ends well. Here's the result:

I designed the PCB for some soviet P416B's that I'm still waiting on, but the cool thing about the Mk. III circuit is how well it accommodates transistors across a wide range of gains/leakages.

For Q1 & Q2, I ended up using a sub-30-hfe pair of chinese 3AX31B's, and for Q3 I used a Philco N501 @ ~120 hfe. I built the circuit to the "Park Fuzz" specs. Still have to tinker around with the biasing, but even a bit gated this thing sounds great.

[umbral peak]

how much was the box?

you can indeed fit anything you like, at most you need to add a resistor on q3 if you don't have enough leakage

[acoustic olive]

15 bucks. Hardly cheap!

Thanks for the advice. I think Q3 just ain't leaky enough. Now that I'm thinking about it, I believe neither of the N501's I have even scratched 1uA on my tester 😛 Time to dig out the other one to confirm.

[acoustic olive]

Inadequate leakage was indeed the culprit. A 1M resistor between collector and base on Q3 fixed the biasing issues.