Synthesis and Synthesizers

GRP Synthesizer at Roma Modulare 2022

Published on 24/05/2023

GRP Synthesizer is a company that specializes in designing and manufacturing high-quality analog synthesizers.

The company was founded in 2005 by Paolo Groppioni, a passionate musician and engineer who wanted to create instruments that combine the classic sound of vintage synthesizers with modern features and reliability.

GRP Synthesizer offers a range of products, from the compact and versatile A2 monophonic synthesizer, to the powerful and expressive A8 polyphonic synthesizer, to the modular and customizable R24 sequencer.

All of the products are handcrafted in Italy, using premium components and meticulous attention to detail.

The whole product catalog was present at the show.

At Roma Modulare 2022 Paolo also brought the just released GRP A1 synth. The first three samples were just built in the early morning of the event to be showcased and tested by the attendees.

GRP A1 at the show
GRP A1 at the show

Let’s go a little deeper with this new product.

GRP A1 new synthesizer

The Grp A1 synthesizer is a versatile and powerful analog instrument that can be used either as a standalone device or as part of an Eurorack system.

GRP A1 close view

It features three internal sound sources: a voltage-controlled oscillator (VCO), a sub-oscillator (SUB) and a noise generator (NOISE), which can be mixed and shaped by a low-pass filter (LPF) with 18dB/octave slope and resonance control.

The Distortion control is useful to further enhance the device’s possibilities.

The Grp A1 also offers two low-frequency oscillators (LFOs) with different waveforms and rates, one of which includes a sample and hold (S&H) circuit for random modulation effects.

The envelope generator (EG) provides attack, decay, sustain and release (ADSR) parameters for controlling the filter cutoff and the output volume.

The Grp A1 can be powered by a USB type C cable (@2500 mA) or by a standard Eurorack power supply and can be easily removed from its case and mounted on a Eurorack module.

The Grp A1 synthesizer is a compact and affordable way to experience the rich and warm sound of analog synthesis.

The following diagram explains the synth’s block connections as well as the I/O.

GRP A1 Block Diagram

Synth Cafè (media partner of Milk Audio Store for Roma Modulare 2022) has recently published the following video where Enrico Cosimi explains the functions and features of the GRP A1 synthesizer.

GRP A4 synthesizer

The bigger device on the stand was the GRP A4 Synthesizer. The unit is well renowned in the synth community as it is being used by several musicians all over the world.

GRP A4 at the show

The Grp A4 is a monophonic analog synthesizer that offers a wide range of sound possibilities thanks to its audio section derived from the bigger A8 model (not shown at the event).

It has three oscillators with six waveforms each, linear and exponential FM modulation, hard sync and sub oscillators.

It also has a ring modulator, a white and pink noise generator, an audio mixer and a dual filter section with a 24dB/Oct low pass filter and a 12dB/Oct bandpass filter.

Each filter has a separate distortion/level control and can be configured for series, parallel or direct out.

The Grp A4 also features an analog step sequencer with 256 steps, four CV/Gate tracks and one auxiliary track.

The step sequencer can interact with the synthesizer, ring modulator, external signals and internal modulation sources to create nearly infinite sonic combinations.

The Grp A4 is definitely a versatile and eclectic instrument that can go from soft and extremely clean to harder and more aggressive sounds.

GRP V22 vocoder

Next to the A1 set there was the GRP V22 Vocoder. This is a high-quality analog device that allows you to process any audio signal with a 22-band filter bank and modulate it with another signal, such as a voice or a synthesizer.

GRP V22 at the show

The result is a rich and expressive sound that can create robotic voices, harmonic textures, special effects and more.

The GRP V22 Vocoder has a fully analog signal path, with discrete components and no digital processing.

It features a balanced input and output, a noise generator, an external envelope follower, a bypass switch and a dry/wet mix control.

The filter bank consists of 22 bands, each with its own level and pan controls, covering a frequency range from 50 Hz to 10 kHz.

The filter bank can be used as a standalone equalizer or as a vocoder modulator or carrier.

The GRP V22 Vocoder also has a MIDI input that allows you to control the filter bank levels and pans with any MIDI controller or sequencer.

GRP V22 is a versatile and powerful tool for sound design and musical expression, offering a wide range of possibilities for shaping and transforming any audio source.

GRP R24 sequencer

The GRP R24 is an 8x3 analog sequencer based on the powerful step sequencer previously developed in the GRP A8 and A4 analog synthesizers.

GRP R24 at the show

The new R24 is packed with control capabilities with CV/Gate, MIDI and USB connections.

It is a self-powered stand-alone sequencer, with hardware compatibility for mounting on a 5U modular format.

The R24 has 64 memories internal for saving and recalling separate sequences.

Each sequence can be set to 8x2, 16+8 or 24 mode, with any user-selectable step length.

The R24 can act as a CV/Gate sequencer or as a MIDI sequencer, with separate lines for the selection of MIDI notes and for adjusting the speed of the keys in steps.

GRP Eurorack modules

GRP also features a full set of modules for the Eurorack standard.

They were all available for hands-on testing and listening and, in our opinion, they are very well designed and built and… they sound awesome!

GRP Eurorack modules at the show


GRP Synthesizer puts quality analog devices on the market to provide powerful tools for the modern musicians who keep an eye to the tradition.

Don’t lose the opportunity to check them out by yourselves!

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