modular systems » Eurorack modules » sound processors » filters & resonators

FXDf stands for Fixed Filter and that's exactly what this module is about. It features individual inputs for different filter slopes and six outputs with fixed frequency bands.

A digital, voltage controllable resonator very well suited for creating Physical Modeling sounds. Three different resonator modes can be chosen from and a there's a four-voice pseudo polyphony. Two outputs are available, each playing different harmonic structures or different notes in polyphonic mode.
As expected from a resonator it is possible to process audio signals but Rings can also be played exclusively via CVs as it can excite and play sounds by itself. Soundwise there is more than just nylon string imitation but singing tones, cold strings and also very experimental and extreme sounds.

Both flexibility and character are main assets of this dual multi-mode filter module. Of course you can use it as two individual filters but smart normalizations, a common cutoff coupler knob and polarizers at the cutoff CV inputs allow for the use as an outstanding stereo filter. It can sound warm and vintage and even aggressive but it's also fantastic with high resonance. Even sub basses and earthshaking bassdrums are no problem for the RT-451.

This multi mode filter is based around four cascaded OTA filter stages providing a maximum slope of -24dB/octave. There are individual outputs for low-, band- and high-pass but outstanding is the assignable Multi output which offers 27 different filter types. Those can be LP, BP and HP with different slopes or various noth and allpass filters and even a phaser!
Voltage control of resonance is available as well as overdrive and a separate distortion for the Multi section.

1973 - Dave Rossum tackles the core of Moog's cascade filter, revises the rest and uses it as a base for the 2100 low pass filter from the E-Mu modular system.
2015 - the evolution of the 2100, Dave's favorite filter, takes place and the result is just this Eurorack module, the EVOLUTION filter.

Almost entirely voltage controlable low pass filter with resonance, Q compensation, self oscillation with outstanding tracking, then very nice and controllable distortion - and on top of that: continuously morphable slope, from -18 to -36 decibel per octave. In case we kept shtum about the sound so far: it is just fantastic!

Multi mode filter with switchable characteristics: lowpass, bandpass and highpass, based on the filter curcuitry of the Steiner Parker Synthasystem.
It has few controls, but less is more and the sound of this Eurorack classic still is one of our favourites.

MMM VCF stands for M°°g Multi Mode Voltage Controlled Filter and is a dual filter featuring common controls for both filters. For that reason it can be used as a stereo filter but you might as well use it in different filter type combinations as it features individual low pass, band pass and high pass outputs for each filter.

Voltage controlled multi mode filter of state variable topology. Not only being small in size but also sounding very tasty and unique. The slopes are rather flat with -12 and -6dB, providing for a rather smooth sound, unless you actvate the switches for the special parameters for resonance character and overdrive, as it will get wild, gnarly and dirty.

The voltage controllable Eurorack module version of the T-Resonator is an interesant concept of two low pass flters and an effect. As the two filters feature cross-modulation, positive and negative feedbacks and their cutoff frequencies can be modulated by an LFO and an envelope follower, many dynamic and very interesting, partly very experimental sounds are possible which are further processed by the digital effects like delay, physical modeling, FM and more.

Advanced band pass filter whose passband width is variable. There are separate resonance controls for the low and high pass which form the Aperture's bandpass and in addition there are two different feedback types with aggressive character. The resonance has a very distinct, nasal sound and allows for self-oscillation ofboth filters over at minimum five octaves. The module is almost entirely voltage controllable, even parameters which aren't covered by potentiometers.
On the whole it's a very versatile filter module with a vast range of tonal possibilities.

In the category "dual multi-mode filter with normalizations and common control of both cutoffs", ACL presents a State Variable filter with 12dB slope, individual outputs, variable filter routing as well as the variable notch balance known from the Oberheim SEM, blending over from low pass over notch to high pass.

Behind the Philter is none else than the fantastic multi mode filter from the Phenol synthesizer, adapted for Eurorack. At first glance it looks pretty simple and tame, yet soundwise it is completely massive and big filter which grades up the sound of any "slow coach" VCO.

The LxD in a narrow 4HP module in which two different Low Pass Gates carry out their daily task. They were designed to operate independently or combined to form the back end of a synth voice.

The Twinpeak module is not only inspired by the TwinPeak-Resonator from Rod Hordijk's Blippoo Box but also designed by Hordijk especially for Epoch Modular.
It is a dual 12dB filter with variable characteristic, from low pass to a dual band pass with two individually tuneable cutoff peaks. Crossfading between inputs allow for mixed use and an even more sound possibilities.
It is a very unique and igh quality filter that provides for many subtle nuances; use it for audio signals at low resonace settings or use it as a beautiful sound generator by "pinging" it to create percussive bell-like sounds at high resonace settings.

With a narrowness of four HP only this module probably is the smallest multi mode filter with individual outputs. It has a slope of -12dB per octave, voltage control of resonance and a ping input that generates a vactrol-like envelope which modulates the cutoff frequency.

Totally unique is the RxMx (pronounced RixMix) because it combines the organic behaviour of lopass gates with the characteristics of a six-channel mixer and these of a crossfader. The mixer is more a scanner with voltage control addressed selection and modulation of a lopass-gate-channel and/or the number of neighbor channels. "Pinging" creates the simulation of a reverb because of the inert Vactrols' slow decay.

Versatile clone of the russian Polyvoks synthesizer's filter with some fancy extras. The resonance is voltage controllable, both the filter slope of the lowpass respective the bandpass width is adjustable with a potentiometer as is the resonance behaviour. With these functions the D-Tech filter can produce both smooth, ballsy sound but also Polyvoks resonant screams, so typical for the Polivoks. Have it your way. And the module is really adequate for creating very wonderful, wooden drum sounds by "pinging" the filter.

Like any module of the 101-X series also Opto VCF resorts to opto-electronic parts but in this case so-called Opto-FETs are used instead Vactrols which have a avery different behaviour. The module consists of six 6dB filter stages arranged in series. Each stage can act individually as lowpass, highpass or as one of two all-pass filters. Plenty of options to experiment with, from usual filtering to phase shifting effects due to all-pass filters.

The f0 is a digital resonant low pass filter with a VCA and an adjustable curve. With a non-linear curve a stable self-oscillation is possible; combined with the Zoom-function the f0 is a great sinewave generator with a huge frequency range. In linear mode you get a stable and clean digital filter.

Befaco's dual low/high pass filter BF-22 is inspired by the filter of the early MS-20 which is based on the Sallen-Key filter topography. The tendency of sound is obvious- the filter freaks out, screams and is pretty dirty. The resonance is more present than in the original, though and thanks to befaco it is voltage controllable.
The two filters can be used individually and connected in series.

Very nice and pretty compact low pass filter with two simultaneous slopes (-12dB and -24dB). It has voltage control of resonance and can be used as a sine wave oscillator at very high resonance settings.

Version in vintage black design

Faithful clone of the early Minimoog lowpass filter with all transistor pairs selected and matched by hand what was nt the case with the later Minis. The circuitry runs internally with exactly the same operational voltages and the transistors have the same specifications as 45 years ago. AJH Synth added voltage control of reconance and selectable overdrive.

The Pole-Zero contains two functions: number one is a 24dB/octave steep low pass filter which is built with MOSFET transistors, known for their soft, vacuum tube-like saturation and distortion. The saturation parameter can be adjusted with a knob.
Number two is a VCA which is found pre-VCF in the module's signal path and which is used to modulate the filter's amplitude. It's known that you never can have enough VCAs - nice to see one integrated in the Pole-Zero.

A mighty tool for sculpting sounds! It can be: either a triple lnked filter with simultaneous control of low-, high- and bandpass, adjustable spacing between center frequencies and passband width. Or three parallel bandpass filters for creating formants. No matter which mode they are in, the filters always are related to another.
The quality parameter can act like a anti-resonance emphasizing inverse frequencies which has a very specific sound.
It's "trinity" make it possible to create three sine waves when self oscillating. Individual and global in- and outputs allow for spectral crossfading. Individual outputs are great for self-FM'ing parameters.