Moog MF 104 drive?

[winslowj]

Howdy! I was listening to some Moog MF 104m & Minifooger Delay demos, and the pedal sounds really nice, but what really caught my ear was that drive section. So, I immediately looked up the schematic, and found this:

To my not-super-well-trained eye, it kinda just looks like a clean boost, but there's no doubt that there's some serious clipping going on there. Does anyone know where that clipping is coming from? Here's the full schematic:
https://www.synthxl.com/wp-content/uploads/2020/04/Moog-MF-104-Schematics.pdf

[radio]

That s the schematic for the Moog MF104 delay.

I have not the schematic of the drive, only their description of the drive:

The Moog Minifooger MF Drive is a guitar effects pedal designed with the same intelligence as the Moogerfooger effects modules.

The Moog Minifooger MF Drive features a multi-stage filter overdrive with a selectable drive range and a variety of controls, including Gain, Drive, Filter and Tone to customise your sound. The pedal feeds the guitar's signal through a Moog Ladder Filter, boutique FET amplifiers and classic operational transconductance amplifiers (OTAs) to produce reactive overdrive with incredible dynamics and harmonics.

The tone of the MF Drive ranges from a creamy British amp overdrive to the crisp, fuzzy tone of a cranked American tube amp. There's even an input for an expression pedal, which, when used with the Peak switch engaged, uses the onboard filters to offer fuzz wah tones. The MF Drive works well as a dirty boost pedal also, pushing an already cranked high-gain amp for a boosted tone, ideal for lead playing.

[winslowj]

Shoot, sorry, that was a little unclear! I actually meant the drive section of the delay pedal, it has this really nice kinda dark overdrive that I'd love to isolate

[bowanderror]

Sorry to resurrect a dead thread, but I was looking at this schematic the other day and had the same question. You're right in that the Gain control is just a clean boost, but the clipping is coming from the next stage of the circuit: the OTA-based VCA (U5-B).



OTAs like the LM13700 have a differential front end that overdrives quite pleasantly, especially when used without feedback as they are here. They also overdrive at relatively low signal levels, so the simple non-inverting gain stage of U1-A will push the OTA input pretty hard.

Interestingly enough, the MF Drive that u/radio mentioned is basically this same signal flow: a gain stage feeding an OTA-based VCA.