Approximate reading time: 1 Minute
4MS Percussion Interface + Expander

4MS Percussion Interface + Expander  ·  Source: 4MS

The Percussion Interface and Expander can generate gates and envelopes from any audio source but particularly suited to plugging in acoustic drums and percussive sounds to control your Eurorack from your drum kit.

Percussion Interface + Expander

The PI+EXP are a pair of modules that are sold together to pull in audio and output gates and envelopes. You can use it as a pre-amp for microphones and instruments which then get their envelopes followed and transients gated into useful control voltages. We first saw them back in April but now they are ready for release.

The Percussion Interface has a single input which outputs a gate when sound is pumped in. It also generates an envelope and an inverted envelope that either follows the audio or makes use of its own Sustain and Decay levels. A Sensitivity knob helps keep things under control.

The Expander section adds three gain stage options and a nice fat 1/4″ jack socket to better accommodate a microphone, guitar or other audio equipment. It also brings in another envelope and inverted envelope with individual trim.

They are not much to look at but when you see them coupled together with a drummer you get a glimpse of what this module could mean for your Eurorack.

View this post on Instagram

The Percussion Interface (PI) and PI Expander are a pair of Eurorack modules that generate gates and envelopes from acoustic drums, samplers, drum machines and virtually any audio source. Converting microphone, instrument, line and modular signals into CV and clock/gate signals, the PI and PI Expander are suited for synchronizing sequencers or other modules to the rhythm of an audio track or live percussion. The modules can simultaneously be used as a pre-amp for microphones or line-level signals, while generating inverted envelopes useful for side-chaining. The PI module contains all the core functionality and can be used without the Expander to conserve space. The Expander requires the main PI module and adds three gain stage options, a modular-level audio output jack, a 1/4” (6.35mm) input jack, and envelope attenuation capabilities. See link in bio for more info! Music: @don.gero

A post shared by 4ms (@4ms_company) on


The PI+EXP will be available at the end of October for $165.

More information


Leave a Reply

Your email address will not be published. Required fields are marked *