TT4

YoMo Tuned Twin-T notch filter / bass-drum / percussion module

What originally started out as a kick-drum/percussion module has mutated into something rather different.

I designed its predecessor, the TT3, with the former use in mind and it worked rather better than the CMOS-based module that preceded it. It was a bit of a touchy beast, but it sounded pretty good (at least, I think it did)

The TT4 is a 2HP version of that module - same deal, but it also turns out that it can do very interesting things to audio-rate signals. A twin-T filter has two 'arms' - one is a high-pass filter and the other is a low-pass filter; by slightly offsetting them from each other you can filter out a range of frequencies (think of it as a reverse band-pass filter) - depending on the signal, interesting things can happen.

Given a decaying pulse, you will get either a kick-drum-type sound or a more clicky woodblock sound depending on the tuning and level of the input. However, given an audio signal (eg. from a VCO) and a bit of judicious knob-twiddling you can get all manner of spacey sounds, up to and including nerve-shredding self-oscillation. The DV3 dual-AR module is a good companion module.

Use it as an ersatz drum module or as a freaky audio filter - the choice is yours. The drum sound isn't to everyone's tastes but it'd be a boring world if we all liked the same stuff.

Finally, there are now two variations available: the secondary tuning pot is very sensitive and not exactly conducive to on-the-fly tweaking unless you want to run the risk of self-oscillation, so with this in mind I'm offering the module with this pot replaced with a trimmer so you can fine-tune the sound and effectively 'set and forget'. There's no difference in functionality, although obviously it won't be accessible from the front panel. The 'trimmer-fied' version also has a slightly different panel layout (no cutout for the second pot)

The fully assembled module includes a laser-cut, engraved panel made from 3mm opaque black perspex. The panel is 2HP (~10mm) wide and the module is around 54mm deep when mounted due to the size of the daughterboard.

A power cable and a pair of M3x10 mounting screws are provided - if you use M2.5 or 4-40 you will need to provide your own mounting hardware.

https://www.etsy.com/listing/616493478/tt4-tuned-twin-t-notch-filter-bass

HEAR IT:
- Used as a tunable notch filter: https://yomo.interzen.co.uk/samples/tt4-filtermode.mp3
- As a percussion module: https://yomo.interzen.co.uk/samples/tt4-kick.mp3 (crappy quality, unfortunately)

https://www.yorkmodular.co.uk/