Polyphonic Synthesizer:

Modal 002
Modal 008 (for sale)
Moog One 16
Nonlinear Labs C15
Waldorf Quantum
Waldorf XTk30
Wersi Stage Performer

Monophonic Synthesizer:

Casio VL-1 Tone
Dübreq Stylophone
Korg M500 MicroPreset (for sale)
MeeBlip (for sale)
Modal 001 (for sale)
Modal Craft Synth
Modal Skulpt
Modulus monoWave
Moog miniMoog (1979 & 2017)
Moog Minitaur
Moog Prodigy
Moog Sub Phatty
Moog Taurus III
Moog Voyager
Sequential Circuits Pro-One
VacoLoco Zira
Waldorf Pulse (for sale)
Waldorf Pulse 2


Synth-Werk Modular
Synthesizers.com Modular


Korg MS-20 mini (for sale)
TTSH (ARP 2600 clone)

String Machines:

ELKA Rhapsody 610
Eminent 310 theatre (for free!)
Hohner String Vox
Logan String Melody
Waldorf Streichfett
Waldorf STVC

Other Keyboards:

Manikin Memotron
Mellotron Micro


ARP Sequencer (clone)
Baloran TriKo
Behringer Mixer MX2642A
Behringer Mixer MX8000
Behringer Rack Mixer RX1602 (2x)
Boss DR-220E
Digital Raagini
EEH DS 500
Electro-Harmonix Small Stone
Georg Mahr Midi-Ratsche
Ibanez Digital Delay DM1000
IBK 10 Control
Korg K25
Kurzweil XM-1 Expression-Mate
Lexicon Model 200 reverb
Modal Craft Rhythm
Mode Machines Krautrock Phaser
Moogerfooger Ring Modulator 102
Moogerfooger 12-Stage Phaser 103
Moogerfooger Analog Delay 104Z
Moogerfooger Murf 105
Moog MP201
OTO Machines BAM
Roland TR-08
Schrittmacher's Inside
Schulte Compact Phaser (19")
Simmons SDS-V
Strymon Timeline
Synthoma Élkorus
VacoLoco Tron
Waldorf 4Pole
Waldorf EQ27
Wersi Voice (BBD FX)
Waldorf midiBay
Waldorf Becher/Mugs


Access MicroWave controller
Alesis Andromeda A6
ARP (Korg mini) Odyssey
ARP Quartet
Crumar Multiman S
Crumar Performer
EES Midi CV7
ELKA Solist 505
ELKA x705
Emu Emax II
Farfisa Soundmaker
Farfisa Syntorchestra
Grp A4
Hohner ADAM
Hohner String Performer
Jen SX1000
Kawai SX-210
Keio Mini Pops 3
Korg PE1000 (Poly Ensemble)
Korg PE2000 (Poly Ensemble S)
Moog Satellite
Oberheim Matrix 6
PPG waves
PPG wave 2.3 (V8.3)
Rhythm Ace 2l
Roland TR 606
Roland M-VS1
SCI model 700
Seiko DS 202+310
Sound-Art Chameleon
Technosaurus Cyclodon
Vermona Piano-Strings
Waldorf Blofeld
Waldorf microQ keyboard
Waldorf Q
Waldorf XT30
Waldorf Gekko Chords
Waldorf Gekko Arp
Waldorf microWave
Waldorf rackAttack
Waldorf Wave
Waldorf waveSlave
Wersi Baß Synth
Wersi String Orchestra


K. Schulze's "Sense"

Helper Apps:

Hz-2-cent Calculator

M@ail & Impressum

© Till Kopper

Grp A4 this is ex-gear / sold

Grp Synthesizer A4

The Grp Synthesizer A4 is an italian Synthesizer und the smaller brother of the Grp A8 and the bigger brother of the Grp A2. It is a brown wooden cabinet with a black metal frontpanel. The first glance would give you the impression of a semi modular synth. But it is not patchable by cables. But all typical and rather seldom used modulation connections are available by a multitude of switches, some multi stop rotary switches and knobs. All in all there are these sections in the box:

  • 3 VCO, each with 6 waveshapes
    • sine
    • triangular
    • triangular + sawtooth ("sharktooth")
    • sawtooth
    • square/pulse + sawtooth
    • square/pulse
    and linear or exponential FM, PWM, suboscillators (selectable -1 or -2 octaves) on VCOs 1&2, sync on VCOs 2&3 to VCO 1, and more
  • voltage controlled LFO 1
  • LFO 2 with triangle and square/pulse wave
  • Mixer for the 3 VCO and their 2 suboscillators, external audio-in, noise, ringmodulator
  • 2 VCFs
    • lowpass filter with 1 to 4 poles
    • state variable filter with 4 modes
      • 2 pole highpass
      • 1 pole bandpass
      • 2 pole lowpass
      • 1 pole band reject (notch)
  • Envelope 1 (loop-mode, autotrigger)
    • attack
    • (peak) hold
    • decay
    • sustain level
    • sustain time (for loop mode only)
    • release
  • Envelope 1 (loop-mode, autotrigger)
    • attack
    • decay
    • sustain level
    • sustain time (for loop mode only)
    • release
  • VCA
  • Auto Pan with own triangle wave LFO
  • Sample & Hold
  • Noise source (white, pink)
  • Envelope follower
  • MIDI interface with 440 Hz tuninge reference tone
  • analog stepsequencer (2x 8 steps or 1x 16 steps) with 2 quantisizer and flexible routing to individual VCOs pitch, VCOs PWM, VCFs. Variable gate length knob. different play and step repeating modes
  • 1/4" CV and gate inputs and outputs
  • MIDI In and Thru on the back of the housing. And the main switch and AC cable socket is there too. The USB port there is only for updating the firmware of the sequencer logic and the MIDI interface. It is not used for other purposes, so better don't use it unless you are advised to by Grp.

Impressive list of avaiable sections. And with the flexible modulation routings you get as much possibilities as a medium modular synth. And all this without getting tangled in patchcables. But on the other hand, you have to watch for nearly each and every switch unless you like unwanted things happen. So this is not for intuitive grab a knob and set a sound. But except for the MIDI interface and some more exotic possibilities of the step sequencers you will not need to read the manual if you are used to modular synths.

The LEDs are partly red or blue, depending on internal or external trigger or sequencer step modes. This is helping to get some more information without checking the switch positions. These switches are not bad, but if you are not straight in front of this synth, you might not see the switch positions that fast. But this is something that would happen on many modular synths as well, so it is not a problem of this synth design, but rather typical for all synths with such a complex and flexible modulation routings.

This is not a beginners synth. This is a serious synth you need to work on and have your mind on it you while patching. The sound is also a nice one. You get beefy basses to celestial tiny bells. Good classic analog sound. It is not sounding like a Moog or a vintage Korg. It never pretends to copy a classic synth character. This synth is a very well done compact synth for endless modulation fun.
Using it just for a bass or leadline would be like using a sports car in the rush hour.