7 things to know about London Drive

London Drive is a simple but pleasing distortion circuit and a good way to learn soldering.
The circuit is based on the external input and mic pre-amp circuit from the EMS VCS-3, the classic British synth, designed at the EMS studios at 49 Deodar Road, Putney. The same circuit was used in the Synthi-A briefcase.
London Drive is obviously very similar to Mini Drive, which is based on the input circuit from a MiniMoog. It has the same two-in two-out layout to make it easy to patch feedback loops.
Does London Drive sound different from Mini Drive? I think so. To me, Mini Drive has an interesting saggy(?) quality, it reacts strangely to big gain changes, and is very mid-rangey. London drive is clearer, faster(?), brighter, more bass, more treble.
It's a simple discrete circuit: three transistors for the audio, three more to drive the incandescent overdrive bulb. The VCS-3 didn't have a level indicator, so it's just the Moog circuit here. Along with modern transistors, there are also a few minor changes to the VCS-3 circuit to make it work in this context, so purists should look away.
To make feedback patching easier, the bottom output is inverted, the top output isn't. Inversion is done by a very basic transistor phase splitter circuit, so the outputs aren't identical (DivKid explains this in his video below).
Check the Mini Drive documentation and videos for patch ideas and feedback tips.

DivKid's brilliant Distortion Masterclass