A couple builds

[lars]

I've had a couple Madbean boards sitting around for a while, and I've finally had some time to complete them.
First off is a 2022 Collosalus. All I can say is, this was a collosal pain to get dialed in, because of my own choice to go way off the marked trail. I decided to try to follow the original pedal as closely as possible, so I got an old schematic and made the appropriate additions/subtractions. I had some old 1458's and 4558's to spare, so it seemed like a good idea. I also used different transistors just to make it hard on myself. In the end, I had a pedal that "worked", but didn't sound anything like I wanted. Ultimately, I had to make tons of mods to the bias control and the clock circuit. I found that Q5 & Q3 are very critical to the overall sound, and should be closely matched to get it to sound right. I also found a very interesting quirk to the biasing of the MN3007. There seems to be two settings of "correct" operation with the MN3007 in this circuit, and they're basically 90 degrees apart from each other on the bias control. I used the bias circuit on the Wizard schematic from 2009 you can find for the MXR117. At one bias setting, the pedal is very mid-80's rubber band metallic sounding, just like all those flangers people hate. But 90 degrees from that bias setting, suddenly it becomes a liquidy Andy Summers chorus machine, which is very good!
One thing I've noticed is that the Manual control really should be a logarithmic pot. The majority of the control is bunched up in the first 1/4 turn of the pot, and then you get about nothing from noon on. This also happens on my original Ross flanger (which is just an MXR117 with 4558's), so it's a common issue with this circuit.


The next one is the covid-era Rabbit Hole 2020.
My first intention was to build and ELK Sustainer with this, since I was always curious as to how that compared with a regular Big Muff.
I didn't like it. The tone control is just too weird. So I decided to try putting the tone control back to the normal cap value. That was a little better, but it still didn't sound great. So I decided to try swapping out the transistors. I had some random transistors that were in a CD case of all places, and it turns out, they just happened to be old BC239's that had the same markings as ones from mid 70's Rams Head big muffs. I adjusted one resistor in the the tone stack and one capacitor in the clipping stage to match the '75 Rams Head muff and BOOM! A killer-sounding Big Muff was born. This thing rips. Run some mild overdrive into the front end, and it sounds epic. I housed all of it in an old enclosure I had used for a DOD 250 clone, and I used random knobs and slapped a Thomas organ logo on it. All the wear and tear on the enclosure is from real use, so it isn't a relic job. It's now one of my favorite dirt pedals I've ever made. Funny how that happens.

[jimilee]

Wow, very cool! If memory serves, the power supply plays big part in the collosalus as well. I had a hard time finding the right one. I don't remember what I ended up going with.

[lars]

I forgot to mention I ended up with a tiny 15pf cap for C23 in the Collosalus, so the value of that cap can be all over the map. Definitely socket it and try many different ones!
I also found a great mod for the manual control:  solder a 10K resistor across the middle lug to the ground lug of the 50K potentiometer. This gives it much more precise control over the sweep, without affecting the behavior at all on the extreme ends of the rotation. I can get usable effect change all the way to about 2:00 on the rotation now, whereas before it would do nothing past around 9:00. I believe this mod simply mimics an audio taper pot, but it's way easier to implement this than take the pedal apart and change out the whole pot.

[jessenator]

I adjusted one resistor in the the tone stack and one capacitor in the clipping stage to match the '75 Rams Head muff and BOOM! A killer-sounding Big Muff was born. This thing rips. Run some mild overdrive into the front end, and it sounds epic. I housed all of it in an old enclosure I had used for a DOD 250 clone, and I used random knobs and slapped a Thomas organ logo on it. All the wear and tear on the enclosure is from real use, so it isn't a relic job. It's now one of my favorite dirt pedals I've ever made. Funny how that happens.

Very nice!   The old and new decals totally works. I dig it.