SYNTHR4, 4-voice analog Synthesizer with two interchangeable filter models, first look

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French Boutique synth developer SYNTHR has announced SYNTHR4, a new 4-voice analog Synthesizer with interchangeable filter models. 

Last year I reported on the new SYNTHR4. An analog 4-voice Boutique Synthesizer from France with easy-to-change analog filters.

At SynthFest France 2023, I was able to take a closer look at the device. And the development went further since last year.

SYNTHR4 first look

You can now choose from even more different filters, including ARP 4072 (ARP 2600), ARP 4012 (ARP 2600), Moog Ladder, AS3320 (PRO-1), SSI2144 (PolySix), Jupiter-8 (12 or 24dB), Oberheim SEM, Steiner Parker, SVF 3320,  Elka Synthex and Jupiter-6.

Remy Wasselin, the developer of this beautiful, feature-rich analog synth, gave me a first look at SynthFest France 2023.


Article From March 11th, 2022

Two years ago I wrote about a French boutique analog Synthesizer called SYNTR3, where you can select the filter models.  How time flies.

In the two years, the developer has further developed the pre-wired concept and is now showing the SYNTR4, a new version of its analog Synthesizer with an expanded feature set.



Visually there are not many differences. The synth is still embedded in a large wooden case (15kg) with a knobby user interface. But the engine went on.

SYNTHR4 is an analog Synthesizer that can be played paraphonically with 4 voices or duophonic with 2 voices in bi-timbral. The engine consists of four VCOs which can be interconnected very deeply. VCO 1 and VCO 3 (+ or -2 octaves) offers different waveforms (saw, sine, triangle…), allows PWM and frequency modulation (FM) as well as a super saw option in the saw waveform.

VCO 2 and VCO 4 (+ or – 2 octaves) comes with different waveforms, offers sync options between the other two oscillators, PWM, FM as well as cross modulation. There are also two sub oscillators. For additional timbres, you get a white/rose noise generator as well as a ring modulator. Then, the signal flows in a comprehensive mixer with access to all signals including the subs and the ring modulator and free option to route them to the VCA 1 or/and VCA 2.

Then the filter section is again freely selectable, as we know it from the SYNTR3. The synth has two built-in filters and you can choose between the following models during the ordering process. Cool, the developer also offers the filters for sale later, so you can later replace them yourself

Low-pass ARP type 4072, MOOG (transistor ladder), AS3320 LP type Pro-One, SSI2144 type Polysix… all at 24dB per octave or multimode, SEM, STEINER, AS3320 MM at 12dB per octave.

The models are multimode (LP/BP/HP), are resonant and offers rich modulation options via the LFOs, aftertouch, and more.


SYNTHR4 also includes two VCAs with initial gain control, two modulation inputs and two panoramic outputs.

Effects, Modulation, Sequencer…

The signal flow is completed with an effects processor that consists of 8 different effects available for each voice. Including chorus, flanger, reverb, shimmer reverb, echo, echo shimmer, and different delays. Each effect can be tweaked with two parameters and it has a dry/wet option per voice.

On the modulation side, you can work with three ADSR envelopes with velocity, retrigger option and loop mode. All have hands-on control on the interface. There are also two multi-wave LFOs with different frequency ranges and trigger options including aftertouch.

SYNTHR4 has different play option. You can either play it unison with 4 voices, unison 2+2 voices, paraphonic with 4 voices, bi-timbral with 2 voices or even with an arpeggiator or sequencer with a song mode. Yes, there is onboard sequencer. It also supports velocity and aftertouch.

On the back, you can find two main outputs, CV/gate connectivity as well as a full MIDI interface (in/thru) that supports a poly chain functionality. It also includes a USB and USB host port, great addition.

The Synthesizer is operated via the many knobs on the interface but also via the self-built display.

An exciting boutique analog Synthesizer from France. The feature set is very intense and has some cool features. I really like the fact that you can swap out the analog filter models and thus giving the synth a different character.

SYNTHR4 is available now on demand for 3540€. You can order individual filter cards for 150€.

More information here: SYNTHR

Hardware Synthesizer News


  1. Hello,
    there will be 2 additional filters : ARP4012 (A better transistor ladder than the Moog) and a clone of SYNTHEX with 24dB LP, 12dB BP and 24 dB HP.

    Thank you for this review.

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