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Percussion Interface (PI) & PI Expander
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.
The PI Expander connects to the PI with an included ribbon cable and does not require a separate
power header.
The two modules are only available together as a pair.
Percussion Interface and PI Expander features:
• Sensitivity knob, Low/Medium/High gain switch, and clipping LED
• Sustain control to prevent misfires, increase gate length, and control the envelope
• Envelope decay control
• Non-inverted and inverted envelope outputs, useful for side chaining
• Four envelope outputs: two attenuated with independent attenuators, and two non-attenuated
• Envelope following or generation modes
• Gate output for clocking sequencers or any unit with a clock or trigger input
• Compatibility with drums, samplers, microphones, drum machines, etc.
• 1/4" input jack (6.35mm)
4ms Company
User Manual 1.0 – August 3, 2020
Sensitivity
Sustain
Env. Decay
Follow
Gen.
IN
+
Gate
–
Env.
Out
PERCUSSION
INTERFACE
Env. Level
Inv. Level
Env. Out
Inv. Out
Audio Out
Input
PI EXPANDER
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Table of Contents
Summary of Contents for 4ms Company Percussion Interface (PI)
- Page 1 Percussion Interface (PI) & PI Expander 4ms Company User Manual 1.0 – August 3, 2020 Env. Level Sensitivity Inv. Level Sustain Env. Decay Follow Gen. Env. Out Inv. Out Gate Audio Out – Env. Input PERCUSSION PI EXPANDER INTERFACE 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.
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Page 2: Table Of Contents
Table of Contents Setting up your Percussion Interface and PI Expander ......... Controls and Jacks: Percussion Interface ............. Controls and Jacks: PI Expander ................Setting Input Gain ....................Using the PI with Various Sources ................. Envelopes in Gen Mode ..................Envelopes in Follow Mode .................. -
Page 3: Setting Up Your Percussion Interface And Pi Expander
Setting up your Percussion Interface and PI Expander 1. Power off your Eurorack system. 2. On the back of the Percussion Interface you will see two headers: a 10-pin header and an 8-pin header. The 10-pin header connects to a Eurorack power header using the included power cable. Connect the 16-pin end of the power cable to a 16-pin Eurorack power header on your power supply distribution board and the 10-pin end to the PI with the red stripe on the power cable oriented towards the bottom of the module. -
Page 4: Controls And Jacks: Percussion Interface
Controls and Jacks: Percussion Interface IN Jack The IN jack accepts a wide range of signals from microphones directed at acoustic sounds such as drums, electronic drum machines, samplers, guitars, synthesizers, line-level equipment, or any other audio source. With the exception of microphones that require power (phantom-powered and electret microphones), any microphone or piezo transducer will work. -
Page 5: Controls And Jacks: Pi Expander
Controls and Jacks: PI Expander Env. Level Knob The Env. Level knob attenuates the signal of the Env Out jack on the PI Expander. When the knob is turned all the way down, the jack will output 0V (no signal). As the Env. -
Page 6: Setting Input Gain
Setting Input Gain The Percussion Interface boosts low level signals in order to generate gates and envelopes at modular level. There are two controls for adjusting gain: the L|M|H switch sets the gain range, and the Sensitivity pot adjusts within that range. Use Cases L|M|H switch position Range... -
Page 7: Using The Pi With Various Sources
Using the PI with Various Sources The PI has three gain settings (LOW, MEDIUM, and HIGH) and a Sensitivity knob that can be used to generate gates and envelopes from almost any sound source. The best setting for the L|M|H switch is usually determined by the type of sound source, and the Sensitivity knob is usually adjusted until the desired gate and envelope outputs are achieved. -
Page 8: Envelopes In Gen Mode
Envelopes in Gen Mode When the PI is in Gen. mode, it will generate a consistent envelope shape each time it’s triggered. In this mode, the Gate will always fire at the same time as the envelope. When triggered, the envelope will rise quickly with a very fast attack, and then sustain for a period of time set by the Sustain knob. -
Page 9: Envelopes In Follow Mode
Envelopes in Follow Mode Using the PI in Follow mode allows the envelope to directly follow the amplitude variations of the input signal. The velocity of the input signal can be imparted onto the output envelopes. The envelope shape can be more complex than the sustain-decay envelope of Gen. -
Page 10: Velocity Sensing
Velocity Sensing The envelope outputs of the PI can respond to the velocity of the input signal. Velocity is a term usually used for percussive sounds when referencing how hard an instrument is hit (harder means more velocity, and softer means less). When using non-percussive audio sources such as vocals, keyboards, etc, you can think of velocity as a combination of the loudness of the notes (or perhaps the “attack”... - Page 11 When adjusting the PI, consider what type of microphone or sensor is being used, how it is mounted, and what sort of object it’s sensing. For example, piezo discs and contact mics output a wide range of signal levels depending on how firmly they’re attached to the object being struck.
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Page 12: Preventing Misfires And Undesired Gates
Preventing Misfires and Undesired Gates When using the PI to generate gates from drum machines with long decays or drums with lots of resonance, you may experience “misfires”, or undesired gates. This can usually be fixed by adjusting the PI’s Sensitivity and Sustain knobs. For this example, the input signal will be a techno track that has a bass drum with about 150ms of decay. -
Page 13: Calibrating Lockout Time For Gate Out
Calibrating Lockout Time for Gate Out On the back of the PI, there is a trim pot labelled CAL LOCK-OUT. This trim pot controls how quickly the PI is able to re-trigger. It has been calibrated to a period of 100ms, which is equivalent to 10Hz, ten drum hits per second, or 600BPM. -
Page 14: Sidechaining With The Pi
Sidechaining with the PI The PI can be used for sidechaining and ducking effects. Sidechaining is a technique where one audio signal triggers an effect on another audio signal. Ducking is a commonly used form of sidechaining where the kick drum of an audio track will cause the other Env. -
Page 15: Electrical And Mechanical Specifications
Electrical and Mechanical Specifications • Percussion Interface 4HP Eurorack format module • 0.98” (25mm) maximum depth (includes power cable) • 10-pin Eurorack power header • • PI Expander 4HP Eurorack format module • 1.13” (28.7mm) maximum depth (includes expander cable) •... -
Page 16: My Patch Notes
My Patch Notes Env. Level Sensitivity Inv. Level Sustain Env. Decay Follow Gen. Env. Out Inv. Out Gate Audio Out – Env. Input PERCUSSION INTERFACE PI EXPANDER Page...