Synth modules

Notes: Really clever noise-based oscillator from AJH. Drones, sweeps and bleeps aplenty, ranging from tamed to out-of-control filth. Also doubles up as a more conventional ring mod and distortion module.

Supplier's notes:
This 14HP wide module is a voltage controlled noise based oscillator, or noisillator for short. It generates 1/f noise and this is then sent through a feedback loop which allows the noise to be "tuned" to varying degrees depending on the settings of the frequency and resonance controls, or incoming frequency or resonance CV's. The tuned circuit can be FM modulated too, for some thunderous sweeping sounds. We have bright and dark outputs, which are pre and post filter respectively. The Bright output will always have a degree of noise present in the signal, whereas the Dark output can be tuned noise only when 4 pole resonance is selected. We also have an external Sync input, which will reset the resonant waveform, and we also have an Audio input, so that an external signal can be mixed into the resonant loop. Combinations of external waveforms to these two inputs can create some massive drone sounds, or sweeping sync sounds.

There is also an XOR ring modulator, which can be used as a module in its own right too. Lastly, we have an XOR amplifier, which is another independant circuit that can be used to add noise and distortion to any audio signal.

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: Two independent Contour Envelope Generators in a single 12hp wide Eurorack module. These are very accurate replicas of the Model D contour generators, with identical circuitry and component values running on the correct +9.3V and -10v supply voltages of the original; so they exactly replicate the original envelope response along with all of it eccentricities. Extra features include manual trigger buttons and envelope status LED's.

The contour generators played a larger part in the sound of the Model D than many people realise. There are two factors that make them unique, firstly the exponential slope when is used in conjunction with the (near) linear slope of the original VCA which is responsible for the famous Model D "punch". Secondly, the re-trigger behaviour is quite unique, multiple retriggering increases the output level so that either the volume increases incrementally, or the filter opens incrementally with each extra key press.

AJH Synth have added independent Decay switches for each individual Contour Generator rather than the shared switch on the original synthesiser, these switches change the Contour response from AD (switch up) to ADSD mode (switch down).

Notes: AJH Synth have had quite a few customers asking if we can make the gain jumpers on the MiniMod VCF and VCA modules accessible from the front panel, so this 2HP module aims to address this.

The Gain Switch Multi has two switches which connect to the gain jumpers on the VCA and VCF. Switch "up" is the same as having the gain jumper in place, switch "down" is the same as removing the jumper, and gives higher gain.

Using these switches gives a similar effect to the old "headphone out to external input" trick on the original Model D but with a much wider overdrive range, particularly from the VCA.

As an added bonus, AJH Synth have also included a six way passive multi.

Notes: The original MiniMod Glide +Noise module was based exactly on the original Minimoog Model D circuitry, which was designed to be used with the built in Model D keyboard, and because of its vintage design its range was severely limited to 5 or 6 octaves, and it also responded to positive voltages only. Another limitation was that it would not return fully to zero when selecting long glide times, which restricted the range even more.

So we made the decision to re-design the MiniMod Glide + Noise using modern precision parts, and we have come up with an all new circuit which has exactly the same function, but with a hugely extended range. It has the same Glide slope characteristic (a slightly curved Linear Glide) as the Model D on which the MiniMod is based, however in response to many requests from customers we have adjusted the glide up and down speeds so that they are now very similar , which is much more useful in real world applications that the earlier MK1 version which (like the Model D) would glide up considerably faster than it would glide down.

The new Mk2 MiniMod Glide Noise module now has an impressive 14 octave range, and can respond to negative voltages down to -5V. This is a very useful feature, as our MiniMod VCO's will respond to negative control voltages and produce correspondingly low frequencies; so it is now possible to glide down quickly or slowly to crazy sub bass levels! The hold feature has been improved too, it covers the full audio range as well as DC control voltages, and works as a track and hold module with Eurorack signal levels.

A further enhancement is that the Mk2 module can now (using selectable jumpers) transmit or receive pitch CV to the Eurorack power bus; for example, the Glide CV Output can now be directed to the Bus in order to send CV's to (for example) three VCO's via the bus without the need for a passive multi and four patch cords!

The Noise section of the module is unchanged, except that we have slightly boosted the level of the Red Noise output to bring it more in line with Eurorack control voltage levels.

Lastly, it is much shallower - Mk1 Glide Noise had a depth of 54mm, and it was the only MiniMod module that was too deep to fit a skiff style case - and this prevented a full MiniMod system being installed into a shallow Eurorack case. The new MK2 version is only 28mm deep, so this allows both it and a full MiniMod system to be mounted into shallow skiff style Eurorack cases.

Dimensions: 6HP wide, 26mm Deep
Current draw: 36mA Positive, 38mA Negative

Notes: Sometimes real precision is required with pitch control voltages - this module features a super accurate "Cal" output, which is accurate to <1mV over 20V, translates to one cent over 20 octaves! It is ideal for calibrating the scaling of VCO's, indeed we have been using our own version of this circuit to calibrate our own MiniMod VCO's for the last three years.

As well as being a precision voltage source it is also a very accurate voltage adder, it has two channels (A & B) and both full volts (octaves) or 1/12th volt increments (notes) can be either added to or subtracted from the incoming signal. Perfect for adding a voltage offset to the output of a sequencer or it can be used to add switchable octaves to a VCO which only has course and fine tunes controls.

It also has a "mix" output, which allows either A channel on its own, or with the three way toggle switch channel B can either be added to, or subtracted from channel B, and this is in addition to the addition and subtraction per channel mentioned earlier.

Dimensions: 10HP wide, 26mm Deep

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: This is a precision active buffer and multiple. This module has outstanding performance: it features very high input impedance, very low output impedance and an offset voltage of <1mV.

Not all active multi's are born equal, some designs do not fully solve impedance mismatch and tracking problems, or they apply offset voltages to the output and in rare cases can cause more problems than they solve!

AJH Synth have added a very useful (and unique) feature to cure tracking problems: four of the five outputs can be adjusted up or down by +/-5% from the front panel, so that VCO's and VCF's that don't track 1V/Oct exactly can be easily compensated to track correctly without having to re-calibrate the VCO or VCF themselves.

Notes: The WaveSwarm is a waveform animator and all analogue dual channel device.

Each channel simulates up to six VCO's beating in unison with a different beat frequency between each animation. The fixed beat frequencies are generated by twelve onboard LFO's, and the front panel pots control the level of each of the six animators, along with the level of the dry signal to the final mix. In addition to independent channel inputs and outputs it also has an A+B output, which sums the outputs of the two channels, creating an effect similar to twelve VCO's in unison! This is possible because channel B uses slightly different beat frequencies to channel A, they are not identical.

The input waveform can be saw, triangle, sine or wavetable/complex waveforms, in fact most waveforms with the exception of square or PWM waves will give some form of animation.

A soft clip circuit is built in so that at higher signal levels the signal magnitude is limited by rounding the top and bottom of the waveforms, thus slightly softening the sound. There are soft clip LED indicators for both channels.

It can produce huge, fat drones or supersaw type waveforms from a single sawtooth or triangle wave input.