TB-Euro Modules

TB-O, TB-EF, TB-EFA, TB-Super-O

The TB Eurorack range of modules are all inspired by the circuits of the original Roland TB-303. The main “voice” circuits are reproduced with some additional capabilities, tweaks and of course adding CV control where it makes sense. Over the years there have been many modifications published for the 303, most notably the devilfish mods. For these modules we’ve kept most of them true to the original. However, where something like the magic R97 exists in the filter we have externalised them with CV or manual controls.


TB-O is a 303 inspired oscillator, aiming to bring that classic 303 sound to Eurorack. The module faithfully recreates the SAW based core oscillator and the quite frankly terrible square waveshaper circuit – but hey, that’s part of the unique charm that is the 303 sound. The module provides 4 waveform outputs, Saw, Square, Triangle and a strange ‘sine-saw-sharktooth’ with lots of nice harmonics.

Modulation wise, you can finally PWM and FM your 303! With options for manual pot based control or CV control with attenuation.

A modern Eurorack take on the much loved classic, full of weight and heft. Build using NOS components as used in the original 303, not a modern tight SMD clone!

TB-EF takes the classic “3 and a bit” pole low pass filter from the 303 and brings with it the same envelope that is intrinsic to the instantly recognisable 303 filter sweep.

All the usual 303 tweaking is here, cutoff, resonance, envelope modulation and accent. But why not take it a bit further with the “chirp” control, push the resonance into crazy realms. Or push the signal into overdrive with the pre-filter drive control.

Built using NOS components, as used in the original 303, this module when combined with TB-O can give you a classic 303 voice in your rack, but of course can take on many more sonic personalities.

TB-EFA takes the entire “post oscillator” voice circuit from the 303 and brings it to Eurorack.

The same “3 and a bit” pole low pass filter and envelope from the TB-EF but adds the VCA which is controlled by the same envelope, just as in the original 303.

The module provides the same features as the TB-EF, but with the VCA included, you also get full control over the decay of the tone as well as the envelope controlling not only filter modulation but amplifier modulation as well.

The TB-EFA includes two additional controls, the decay of the envelope and the width of the filter. The width allows you to control the extent to which the filter mashes up the sound, from subtle to shrill, the options are endless.

Example patch with TB-O and TB-EF using an MSW chronovore to sequence through an external VCA with fast acting envelope control.

TB-Super-O is a 3 oscillator version of the 303 Square and Sawtooth.

Supersaw your 303 anyone? This module came about after hearing some nice phasing when running two TB-O modules with the same pattern. Now you can supersaw and supersquare your 303 for some truely unique tones.

Each oscillator has its own tuning control and the CV V/Oct input is normalised across all 3 oscillators when the second and third CV inputs are not used.

The TB-Super-O is in prototype form at present and should be available soon via the usual routes.

TB-Super-O and TB-EFA in action.