A New Electric Mistress Clone - With a Dinosaur Theme!

The Electro-Harmonix Electric Mistress is one of the foundation modulation effects pedals released in the 1970's. It has been used by many guitar luminaries over the years, and is a really amazing flanger / chorus pedal. I'd previously built the PCB Guitar Mania version of the board - though it appears that this was a copy of the Madbean Current Lover board as it had many of the same quirks. Madbean has recently released a 2023 revision of the board that adds a volume knob, support for multiple BBD chips, and multi-voltage support (up to 18V). While my previous build was a great pedal, I really wanted to do a fun dinosaur version to add to my Steggo line-up. I'd also gotten requests for an Electric Mistress clone from some friends, and I really wanted to go with a better base PCB than on my original build, so I grabbed a few of the new Madbean boards and got to work!

As you can see from the board above, there are a lot of ICs that go into cloning the Electric Mistress. By and large these are all new production from Mouser, but I am using a vintage MN3007 BBD chip I picked up locally (...and by picked up I mean I bought them out). The rest of the components are all new as well. The resistors are 1% metal film Yageo and KOA Speer, the film caps are a mix of WIMA, Kemet, and one Panasonic. All of the electrolytic capacitors are from Nichicon. I socketed all of the ICs as well.

Because the build supports multiple BBD chips and voltages, you have to make a few decisions when populating the board (unless you want to socket a few extra components). There are a couple of places for jumpers in the middle of the board that let you set what type of BBD you're using. As I planned to run these using the MN3007 at 18V, I went ahead and hard wired the jumpers rather than socketing them, though that is an option. However if you change voltage and/or BBD, you'll need to completely recalibrate the unit (see below for details). There is also space for a regulator that is only used if you're running at 18V, but as with the jumpers it can be socketed. I hardwired mine.

Once the pedal is together, it has to be calibrated so I got Steggi to help with the that! The Madbean instructions are really very good and they walk you through the whole process - starting with basic transistor biasing and then setting the limit for the BBD and the clock rate. This can all be done by ear which makes things much easier than pedals you have to pull out the oscilloscope for!

The whole pedal fits snugly, but very comfortably in a 1590BB2 enclosure. Because I wanted to route the input and output audio wires as far away from the circuit as possible (to limit any tendency for the effect to pick up noise), I decided to go with Lumberg jacks rather than my normal Switchcraft as they kept the audio path well away from the PCB. You can just see the black and purple input / output wires running along the left hand side (from the bottom) of the enclosure around to the back where they connect in to the jacks. I went ahead and braided the power and ground wires together and hooked them into the DC jack. This design had well-placed pads for the audio jack grounds, so I used them to keep those lines short. All of the connections to the jacks are insulated with heat shrink tubing.

I wanted to do some thing fun for the enclosure, and our mascot this time is the Minmi. According to Wikipedia:

"Minmi is a genus of small herbivorous ankylosaurian dinosaur that lived during the early Cretaceous Period of Australia, about 120 to 112 million years ago. In 2016, Gregory S. Paul estimated its length at 3 metres (9.8 ft), its weight at 300 kilograms (660 lb). For an ankylosaurian, Minmi had long limbs, perhaps used to quickly search cover under brushes when threatened by large predators which might have been able to flip the small animal on its back."

The artwork here was done and published by Tuomas Koivurinne, who kindly gave me permission to use it on the pedal.

This new version of the Electric Mistress was originally commissioned by a friend who wanted their personal logo added, and decided to go with a slightly different LED - so his version is above.

In terms of the sound, it really captures the old school Electric Mistress perfectly, with some added functionality. It is also extremely quiet! While I could hear some very faint "swoosh" during initial testing, once I got the pedal actually boxed-up in the enclosure, that disappeared. While my previous build was reasonably quiet, you could still hear some slight modulation of the baseline audio signal in some cases. I haven't pushed this one to the limits yet, but it does seem to be a much better layout overall!