JoMox Mod FM 8-Voice Eurorack FM Synthesizer

The Mod FM is a completely self-contained 8 voice FM synth in eurorack format, which can create powerful sounds out of the box without lacking the commonly provided CV modulation possibilities.

It provides 4 Operators and 2 LFOs/VCOs per voice. Additionally it has 2 analog filters and analog VCAs per voice which apply analog warmth and depth to the Mod FM, although the FM engine is digital of course.

Each voice has own CV/Gate inputs and an individual output. There is a mix output which separates even and odd voices. Here you can mix internal effects like delay and reverb to the stereo output signal.

Next to the CV/Gate control, the Mod FM has Midi in and out in TRS type A format and a USB C connector which handles Midi too.

Even without diving too much into complicated modular setups you can create extremely good sounding and metallic FM sounds, snappy bases but also soft and deep sounding analog style sounds.

Furthermore, the Mod FM offers a variety of external cv modulations in order to e.g. modulate each operator individually or control the FM envelopes.

The Mod FM is fully multitimbral, i. e. each voice can play an own sound in Multi Mode which gets stored as a complete multi set (not only vectorized). That is, you can copy a single sound to the desired multi, but editings made on that particular multi get stored along with the multi set.

Hence, we have the biggest advantage of the hybrid approach:

Modular is great but can be very complex, and you might be trapped in a system where you never reach again the desired sound of the latest session. Storeability certainly helps.

The different sections in more detail:

Matrix FM:

4 operators are arranged in a matrix, in which every operator (= sine oscillator) can be modulated by each one of the other three.

The 16 endless potentiometers of the matrix adjust the modulation amount (FM amt) and the base frequency of the operators.

For each operator you can change the base frequency by the diagonal knobs.

There are several overtone modes that determine if one operator is controlled by the keynote (or CV) = base operator, or if it's locked in as overtone (= overtone operator) to the assigned base operator. For the base operator, the number resembles xxx semitones added to the keynote.

For the overtone operator, the adjusted number is the xxx = Nth overtone or harmonics to the base operator frequency.

The locked overtone operator tracks the base operator and is still able to modulate and being modulated.

Each operator has an ADSR envelope. This envelope can also be used to frequency-modulate the operator.

Algorithm:

The algorithms from the known FM sythesis are actually special cases to the whole matrix.

Because it gets pretty quickly uncontrollabe if you turn all the knobs because of the feedbacks, we have decided to implement the algorithms. There are 26 algorithms, that are derived from the DX9 with its 4 operators.

At this menu it's even possible to change the frequency mode of each operator to a fixed frequency that is edited in single Hz and which does not follow the keynote, but only modulation. That makes sense for e.g. percussive sounds.

LFO/VCO:

Each voice has 2 LFOs which can modulate either the frequency (FM) or the amplitude (AM) of an operator. Every LFO adresses 64 different wave forms that are displayed in the right OLED display.

There is another feature: each LFO can be switched into a VCO that covers the whole audio range. You can even mix it into the signal chain and it tracks to the keynote. The former LFO rate parameter turns into a detune parameter. That is, you can create classic sounding rectangle/sawtooth analog basses or string pads – and much more of course.

Filter:

Each voice contains an analog filter which is build up with the chip SSI2140 from Sound Semiconductor, which is an improved modern version of the old SSM2040, designed by Dave Rossum, and which had been used in Oberheim synths and the early SCI Prophet-5.

The filter has a classic 24dB output and a 12dB state-variable multimode-filter. The three basic characteristic outputs LP/BP/HP can be cross-faded continuously with one parameter called shape.

Both filter outputs 24dB/12dB can be mixed independently.

The ADSR for the filter ist fast and cuts in very quick and directly, the resonance is well adjustable.

The filter section contains an own LFO for the cutoff which is independent from the digital sound engine and has also 64 waveforms.

The VCA is a fast transistor-vca which is important for snappy sounds. The same transistor-vca is used in all Jomox drum products. Therefore the ModFM can be used as a rich source for technoid drums and percussions of any kind.

On the analog voice board there is another sound source: Metal Noise. It can be mixed into the filter independently from the digital engine (= FM synth) and offers again an inexhaustable pool of weird sounds.

FX:

The Mod FM also has an FX section added: reverb and 2x delay. These only work on the stereo mix output. The delay can be beat-synchronized via midi clock and offers a very short delay time in millisecond range. That gives you flanging and oil-can-like effects.

Specifications

+ 8 voices fully multi timbral FM synth

+ 4 operators per voice

+ Full modulation matrix / 26 algorithms

+ 2 LFO/VCOs per voice

+ CV/Gate per voice

+ CV modulation inputs per operator

+ Outputs for each voice plus mix out

+ True audio FM modulation inputs

+ True analog filters per voice

+ 24db low pass

+ 12dB multimode LP/BP/HP cont. shape

+ True analog VCAs per voice

+ Midi TRS type A

+ USB C device

+ Digital reverb, 2x stereo delay

+ Full storeability, also CV amounts

+ 128 presets, 118 multi sets

+ 2x 128x64px OLED displays

Power consumption:

+12V: 370mA max.

-12V: 170mA max.

Total power: 6,5W

Dimension:

Size: 56 HP = 284mm

Height: 3 RU = 129mm

Depth: 40mm