AJHSynth

Notes: The Random Voltage Event Generator (RVG) is a faithful replica of the vintage EMS Random Voltage Generator. It produces random voltages which vary smoothly or in a step-wise manner. Random timing pulses are also available. The rate of change of all outputs is voltage controllable over a wide range.

Just like the original RVG it uses four unijunction transistors - three of them are configured as ramp and hold generators and the fourth is an LFO. It produces two separate random voltages but also the clock time between pulses can be randomised.

The module offers some extra features: it is possible to add a bias voltage to either of the random voltage outputs, and also add slew to Voltage 1. There is a CV control of the LFO frequency and clock speed as well as CV control of the Time variance.

The internal LFO can be tapped thanks to dedicated outputs for both sawtooth and triangle waveforms, and the waveform shape follows the time variance. The internal clock can be started using an external gate or with the help of the manual trigger button that works when the clock is stopped.

The TR-IN input allows an external clock to be used instead of the internal LFO. There is also a gate output, the gate length changes in proportion with the time variance, and the duty cycle of the gate can be varied from 1% to 99%.

*limited edition!

Module Width: 14hp

Module Depth: 26mm (Including power lead)

Current Usage: 95mA Positive, 70mA Negative

Notes: Black version of AJH's random voltage generator, based on the ultra-rare 1970s EMS RVG. Complex, triggerable modulation source with multiple outputs and full CV control.

Supplier's Notes:
The Random Voltage Event Generator (RVG) is a faithful replica of the vintage EMS Random Voltage Generator. It produces random voltages which vary smoothly or in a step-wise manner. Random timing pulses are also available. The rate of change of all outputs is voltage controllable over a wide range.

Just like the original RVG it uses four unijunction transistors - three of them are configured as ramp and hold generators and the fourth is an LFO. It produces two separate random voltages but also the clock time between pulses can be randomised.

The module offers some extra features: it is possible to add a bias voltage to either of the random voltage outputs, and also add slew to Voltage 1. There is a CV control of the LFO frequency and clock speed as well as CV control of the Time variance.

The internal LFO can be tapped thanks to dedicated outputs for both sawtooth and triangle waveforms, and the waveform shape follows the time variance. The internal clock can be started using an external gate or with the help of the manual trigger button that works when the clock is stopped.

The TR-IN input allows an external clock to be used instead of the internal LFO. There is also a gate output, the gate length changes in proportion with the time variance, and the duty cycle of the gate can be varied from 1% to 99%.

*limited edition!

Module Width: 14hp

Module Depth: 26mm (Including power lead)

Current Usage: 95mA Positive, 70mA Negative

Notes: Perfect for adding that final touch to a modular patch, the AJHSynth Finaliser R-EQ module includes seven Mono / Stereo reverb types, along with a four band equaliser and a Sonic Maximiser / Enhancer.

The Reverb, EQ and Maximiser can be used in Mono IN, Mono OUT mode or Mono IN, Stereo OUT modes. The reverb alone can also be used in Stereo IN / Stereo OUT mode too.

The fully analogue four band Equaliser includes three parametric equalisers for Low, Low Mid and High Mid ranges, and the High EQ has switchable shelving of either 2kHz or 5kHz. The Low EQ also includes a shelving mode.

The Maximiser is a fully analogue circuit too, with low and high treatment bands which change the phase and amplitude relationships of the sound to add punch and harmonics and really bring the sound to life in the mix.

The Reverb engine is based on 20 year old DSP technology, harking back to the reverb units which were used extensively on many synth and EDM tracks a couple of decades ago. We have added full control of reverb wet / dry mix, either manually or under CV control.

Notes: Perfect for adding that final touch to a modular patch, the AJHSynth Finaliser R-EQ module includes seven Mono / Stereo reverb types, along with a four band equaliser and a Sonic Maximiser / Enhancer.

The Reverb, EQ and Maximiser can be used in Mono IN, Mono OUT mode or Mono IN, Stereo OUT modes. The reverb alone can also be used in Stereo IN / Stereo OUT mode too.

The fully analogue four band Equaliser includes three parametric equalisers for Low, Low Mid and High Mid ranges, and the High EQ has switchable shelving of either 2kHz or 5kHz. The Low EQ also includes a shelving mode.

The Maximiser is a fully analogue circuit too, with low and high treatment bands which change the phase and amplitude relationships of the sound to add punch and harmonics and really bring the sound to life in the mix.

The Reverb engine is based on 20 year old DSP technology, harking back to the reverb units which were used extensively on many synth and EDM tracks a couple of decades ago. We have added full control of reverb wet / dry mix, either manually or under CV control.

Notes: This 30HP wide module features twelve fixed frequency, inductor based bandpass filters, set at half octave interval spacing and covering from 125 Hz through to 5.8kHz. It also features low pass and high pass shelf filters, again they are fixed frequency and both are active inductor based circuits. It has a vintage pedigree that harks back to the original and highly sought after 914 Fixed Filter bank from the 1960's Moog 900 series modular synthesiser system, however we have brought this design up to date and made it compact enough to fit into skiff friendly Eurorack cases by using gyrator based active inductors, and have added some other very useful features too - the bands are split alternatively to left and right channels, each having their own individual output, and there is also an inbuilt Voltage Controlled cross-fader that allows panning between the left and right banks, with a mix of all bands available in the central position.

In addition, we have a second cross fader that can mix between the dry incoming signal, or an external signal fed into input 2, and this is cross-faded against the wet MIX Output - this allows Voltage Controlled crossfading from wet to dry signals, or between wet and external signals - and the level of each can be adjusted using the Input 1 and Input 2 level controls.

A further addition is the feedback control, this is similar in design to the resonance control on a regular VCF, but because of the multiple fixed filters topology it is rather different in operation - it would normally be added in small amounts to thicken up the sound, however we have allowed the feedback to traverse to quite extreme settings for howling feedback and even soft clipped self-oscillation, especially for the noise merchants out there...

Using L/C inductor topology bandpass circuits rather than the usual Sallen Key R/C active bandpass filters does give a slightly different sound and this is part of the magic of the original 914 filterbank, as the LC based circuit exhibits less phase shift against frequency that the more common Sallen Key R/C based bandpass filters that are used in many Modular synths.

Many people often wrongly assume that a fixed filter bank is exactly the same as a graphic equaliser - however this is certainly not the case, if all of the controls of a graphic EQ are set to centre then a flat frequency response is expected and the output will sound very similar, or identical to the input - this does not happen with a fixed filter bank, the frequency response rises and falls as it passes between each stage (but to a lesser extent than if the filters are all set to maximum output), so it acts as a soft slope comb filter, and the resulting output sounds very different from the input signal. Also, with all of the individual filters turned to zero there will be no output at all.

Notes: The Gemini 2412 is a creamy, extremely fat sounding dual filter based on vintage Oberheim SEM circuits. In addition to high-pass, band-pass and low-pass, there is the infamous variable filter type, which allows you to blend between several characteristics. Thanks to its dual concept, serial and parallel modes of operation and an ingenious modulation system, the Gemini 2412 should not only be able to achieve classic, extremely bulbous results, but also wafting stereo effects and lively formant sounds.

Notes: The Gemini 2412 is a creamy, extremely fat sounding dual filter based on vintage Oberheim SEM circuits. In addition to high-pass, band-pass and low-pass, there is the infamous variable filter type, which allows you to blend between several characteristics. Thanks to its dual concept, serial and parallel modes of operation and an ingenious modulation system, the Gemini 2412 should not only be able to achieve classic, extremely bulbous results, but also wafting stereo effects and lively formant sounds.

Notes: Serious versatility from AJH here. Based on the circuits from the Oberheim Matrix 12, the Matrix VCF offers a whopping 16 different fully analogue filter modes, each with two different resonance models. All bases covered.

Supplier's Notes:
Presenting the new AJHSynth Matrix VCF - this may well be the most versatile Eurorack VCF ever.

This amazing multimode filter and VCA offers sixteen different filter types, and two different resonance models on each, totalling an incredible thirty two assorted resonant filters to choose from. AJH Synth have also included manual and CV control of filter type selection, along with 16 LED's that give a clear visual indication of which filter type is currently selected.

The filter core circuitry is based on that of the rare and highly sought after Oberheim Matrix 12 synthesiser, and of course has an all analogue signal path. The Matrix 12 VCF originally offered fifteen filter types, however AJH Synth have expanded this to 16 with the addition of AP4, a full four pole all pass phaser mode.

AJH Synth have added a unique P-Vox resonance distortion and overdrive circuit that changes the character of the resonance completely, and can force all of the filter modes into self oscillation. This effectively doubles the filter variants and hugely broadens what is already a very impressive sound pallet.

Other features include an inbuilt VCA with Input and Output Level controls, a Peak level LED, CV control of resonance, and of course the legendary AJHSynth build quality.

The Matrix VCF in depth

After two years of development AJH Synth have finally released what they consider to be the most versatile Eurorack VCF & VCA ever. Like many other AJHSynth modules it uses the very best vintage analogue circuitry as the starting point for the design, and in this case, the filter was chosen from the rare and very desirable Oberheim Matrix 12 synthesiser. AJH Synth expanded this from the original fifteen filter compliment to sixteen distinct filter types by adding in a really useful four pole phaser!

So, behind the compact 14hp front panel lies sixteen distinct filter types, including all of the favourites: Low Pass filters with a choice of one, two, three or four poles, Band Pass filtering with two or four poles, High Pass filtering with one, two or three pole options, along with Notch filtering and four complex, combination filter types. Finally, a four stage phaser with two types of emphasis that can be forced into tuneful self-oscillation!

However, this is far from the end of the story. AJH Synth decided to use their design expertise to add in some crazy resonance distortion circuitry, that could be switched on from the front panel. This was inspired by the filter from the Soviet Polivoks synthesiser, but again the implementation used here is considerably changed, improved, and best of all this can be applied to all filter types! This completely changes the filter character when engaged, and it forces all of the filters into self-oscillation at higher resonance settings. Better still, the oscillation waveforms are more harmonically rich than the usual sine waves - everything from gloriously fat to screaming and angry! Best of all, this takes the number of different filters up to a massive thirty two variations!

AJH Synth put a lot of thought into the ergonomics and how to select the individual filter type. Filter type can be changed either with the front panel Mode knob, or by using a control voltage patched to the MODE CV input. The selected filter mode is displayed by the LED next to the filter in use. This is also very helpful when using a step sequencer to change filter mode as it gives a real time display of the filter chosen as you take the step CV voltage up or down, while setting up each individual step.

Lastly, AJH Synth have also included a VCA hard-wired to the output - simply patch an envelope or an LFO to the VCA input, connect a VCO to the audio input and you have a synth voice (with a choice from 32 different filters!) using only three modules!

Thirty two Eurorack VCF's and a VCA would most certainly take up a lot of rack space - AJH Synth have got all of this into 14hp and managed to have a really finger-friendly user interface, without it feeling cramped.


Sixteen distinct filter modes to choose from

Here's a list of the different filter modes that are available:
1 - Four Pole Band Pass
2 - Three Pole High Pass combined with One Pole Low Pass
3 - Three Pole All Pass combined with One Pole Low Pass
4 - Two Pole Notch combined with One Pole Low Pass
5 - Two Pole Low Pass
6 - Four Pole All Pass (Phaser)
7 - Four Pole Low Pass
8 - Two Pole Band Pass
9 - Two Pole High Pass combined with One Pole Low Pass
10 - Three Pole High Pass
11 - Three Pole All Pass
12 - Two Pole Notch
13 - One Pole Low Pass
14 - Two Pole High Pass
15 - Three Pole Low Pass
16 - One Pole High Pass

All of the above filter types can be further altered by switching in P-Vox mode, this doubles the list up to thirty two different filter variants!

P-VOX MODE

Transforming the resonant character of every filter type

This magical switch completely transforms the resonance of the filter core by overdriving it in a similar fashion to the filter from the Soviet Polivoks synthesiser, which was renowned for it's powerful, aggressive character.
In common with the Oberheim Matrix 12 VCF, some of the sixteen filter types will not normally go into self-oscillation, however when you switch on P-Vox mode all sixteen filter types can be forced into self-oscillation at higher resonance settings. But that isn't the only change, the self-oscillation waveform is not the usual sine waveform, it is a rather more interesting and harmonically rich waveform that varies according to the filter type chosen - generally Low Pass modes produce the nearest to regular sine waves, whereas other filter types can produce very much more complex waveforms as can be seen in the diagrams below. It does not require any audio input for this, it can be a stand alone oscillator. Most of the filter types will track 1V/Oct reasonably well over a three to five octave range, so it can be used as a VCO with a few interesting waveshapes!

Of course, P-Vox mode isn't just useful for self-oscillation, it adds lots of character to any audio signal as P-Vox resonance is switched in.

Module Width: 14hp
Module Depth: 29mm (Including power lead)
Current Usage: 56mA Positive, 36mA Negative

Notes: Presenting the new AJHSynth Matrix VCF - this may well be the most versatile Eurorack VCF ever.

This amazing multimode filter and VCA offers sixteen different filter types, and two different resonance models on each, totalling an incredible thirty two assorted resonant filters to choose from. AJH Synth have also included manual and CV control of filter type selection, along with 16 LED's that give a clear visual indication of which filter type is currently selected.

The filter core circuitry is based on that of the rare and highly sought after Oberheim Matrix 12 synthesiser, and of course has an all analogue signal path. The Matrix 12 VCF originally offered fifteen filter types, however AJH Synth have expanded this to 16 with the addition of AP4, a full four pole all pass phaser mode.

AJH Synth have added a unique P-Vox resonance distortion and overdrive circuit that changes the character of the resonance completely, and can force all of the filter modes into self oscillation. This effectively doubles the filter variants and hugely broadens what is already a very impressive sound pallet.

Other features include an inbuilt VCA with Input and Output Level controls, a Peak level LED, CV control of resonance, and of course the legendary AJHSynth build quality.

The Matrix VCF in depth

After two years of development AJH Synth have finally released what they consider to be the most versatile Eurorack VCF & VCA ever. Like many other AJHSynth modules it uses the very best vintage analogue circuitry as the starting point for the design, and in this case, the filter was chosen from the rare and very desirable Oberheim Matrix 12 synthesiser. AJH Synth expanded this from the original fifteen filter compliment to sixteen distinct filter types by adding in a really useful four pole phaser!

So, behind the compact 14hp front panel lies sixteen distinct filter types, including all of the favourites: Low Pass filters with a choice of one, two, three or four poles, Band Pass filtering with two or four poles, High Pass filtering with one, two or three pole options, along with Notch filtering and four complex, combination filter types. Finally, a four stage phaser with two types of emphasis that can be forced into tuneful self-oscillation!

However, this is far from the end of the story. AJH Synth decided to use their design expertise to add in some crazy resonance distortion circuitry, that could be switched on from the front panel. This was inspired by the filter from the Soviet Polivoks synthesiser, but again the implementation used here is considerably changed, improved, and best of all this can be applied to all filter types! This completely changes the filter character when engaged, and it forces all of the filters into self-oscillation at higher resonance settings. Better still, the oscillation waveforms are more harmonically rich than the usual sine waves - everything from gloriously fat to screaming and angry! Best of all, this takes the number of different filters up to a massive thirty two variations!

AJH Synth put a lot of thought into the ergonomics and how to select the individual filter type. Filter type can be changed either with the front panel Mode knob, or by using a control voltage patched to the MODE CV input. The selected filter mode is displayed by the LED next to the filter in use. This is also very helpful when using a step sequencer to change filter mode as it gives a real time display of the filter chosen as you take the step CV voltage up or down, while setting up each individual step.

Lastly, AJH Synth have also included a VCA hard-wired to the output - simply patch an envelope or an LFO to the VCA input, connect a VCO to the audio input and you have a synth voice (with a choice from 32 different filters!) using only three modules!

Thirty two Eurorack VCF's and a VCA would most certainly take up a lot of rack space - AJH Synth have got all of this into 14hp and managed to have a really finger-friendly user interface, without it feeling cramped.


Sixteen distinct filter modes to choose from

Here's a list of the different filter modes that are available:
1 - Four Pole Band Pass
2 - Three Pole High Pass combined with One Pole Low Pass
3 - Three Pole All Pass combined with One Pole Low Pass
4 - Two Pole Notch combined with One Pole Low Pass
5 - Two Pole Low Pass
6 - Four Pole All Pass (Phaser)
7 - Four Pole Low Pass
8 - Two Pole Band Pass
9 - Two Pole High Pass combined with One Pole Low Pass
10 - Three Pole High Pass
11 - Three Pole All Pass
12 - Two Pole Notch
13 - One Pole Low Pass
14 - Two Pole High Pass
15 - Three Pole Low Pass
16 - One Pole High Pass

All of the above filter types can be further altered by switching in P-Vox mode, this doubles the list up to thirty two different filter variants!

P-VOX MODE

Transforming the resonant character of every filter type

This magical switch completely transforms the resonance of the filter core by overdriving it in a similar fashion to the filter from the Soviet Polivoks synthesiser, which was renowned for it's powerful, aggressive character.
In common with the Oberheim Matrix 12 VCF, some of the sixteen filter types will not normally go into self-oscillation, however when you switch on P-Vox mode all sixteen filter types can be forced into self-oscillation at higher resonance settings. But that isn't the only change, the self-oscillation waveform is not the usual sine waveform, it is a rather more interesting and harmonically rich waveform that varies according to the filter type chosen - generally Low Pass modes produce the nearest to regular sine waves, whereas other filter types can produce very much more complex waveforms as can be seen in the diagrams below. It does not require any audio input for this, it can be a stand alone oscillator. Most of the filter types will track 1V/Oct reasonably well over a three to five octave range, so it can be used as a VCO with a few interesting waveshapes!

Of course, P-Vox mode isn't just useful for self-oscillation, it adds lots of character to any audio signal as P-Vox resonance is switched in.

Module Width: 14hp
Module Depth: 29mm (Including power lead)
Current Usage: 56mA Positive, 36mA Negative

Notes: Mega-Phase 12 is an analogue stereo phaser with beefy, very vocal sound. The module is based on the effect pedal Small Stone developed by Electro Harmonix. In contrast to the classic, here you don't have four, but up to twelve stages at hand. The resonance can be picked up from different points in the signal path. Thanks to several inputs and outputs, it is possible to patch a second, external feedback loop with additional effects. Without a doubt the most flexible phaser module on the market.

Notes: The next generation 12 stage, analogue multi tap Phaser, which is a development of, and replacement for, our earlier MegaPhase 12 unit. It includes all the features of the MegaPhase 12 and is also built around the circuitry of the superb sounding EH Smallstone Phaser, which was used to such great effect on synthesisers and string machines by J M Jarre on his early albums. It has the same versatile Stage and Emphasis stage switching, and the same configuration of stereo outputs, where the left channel is taken from the Stage switch, and the Right output from the Emphasis Stage Switch.

New features include independent Level Controls for Input 1 and Input 2, and a Phase "Colour" Control, which can lighten or darken the phasing effect. We have also used much lower noise internal VCA's and low noise audio op-amps along with a four layer PCB design, so that the S/N ratio is improved and the noise floor is considerably reduced compared with the previous MegaPhase 12 phaser. Like its predecessor it occupies 18HP of Eurorack space.

Notes: A beautiful sounding and versatile next generation analogue phaser, with many added features which combine to take all pass phase shifting to a completely new level. The circuit design is based on the critically acclaimed vintage "Small Stone" phaser, expanded from 4 to 12 stages. We have fitted a unique multi tap switching system which allows stages to be individually selected for both the Output and Emphasis return path, allowing a huge variety of phasing sounds.

Features include two inputs with independent Level Controls, and a Phase "Colour" Control, along with a "Wet" output. We have included CV inputs for voltage control of both Phasing Depth and Emphasis (Resonance) levels, so that these can be fully controlled from other Eurorack modules or external voltage sources. It can be used in Mono IN, Mono Out mode or Mono IN, Stereo OUT modes, with the stereo outputs taken from the Stage and Emphasis paths.

In addition to a manual Frequency control it includes two separate Frequency CV inputs; FCV1 and FCV 2 with an attenuverter. An inbuilt, wide ranging LFO is normalised to FCV 1 input, and an LFO output jack allows the internal LFO to be used as a modulation source for other Eurorack modules.

Module Width: 18hp

Module Depth: 26mm (Including power lead)

Current Usage: 90mA Positive, 85mA Negative