New Eurorack Manufacturer AJH SYNTH

Big Fat Sawtooth from Andrew Whiteley on Vimeo.

It looks like we have a new Eurorack manufacturer in town. AJH SYNTH. The following is their module line-up captured for the archives.  Click through on each or go straight to their website for additional details and video. They also have cases, PSUs & a MIDI/CV converter in the works. This one in via PatchPierre.Net.

VCO - Oscillator

"The discrete transistor core of this Voltage Controlled Oscillator is an exact emulation of the original and now very rare R A Moog Model D Oscillator from 45 years ago, and the resulting waveforms and sounds are exactly as the original, as big, fat and sweet as ever!

It features front panel switchable octave selection and four independent waveform outputs including the famous “Sharktooth” wave, Sawtooth wave, Square wave and Triangle wave.

The Square wave output now has fully adjustable Pulse Width Modulation, with manual and CV control rather than the more restricting selection of two static fixed pulse widths or square wave of the original design.

We have added extra features too, including exponential and linear modulation inputs and two different types of oscillator sync which help to make this a very versatile Eurorack VCO in its own right.

Module Width: 14hp
Module Depth: 34mm
Current Usage: 70ma"

VCF - Filter

"The stuff of legends, the Moog transistor ladder filter changed the face of the musical landscape forever. The MiniMod VCF is a faithful replica of the filter used in the early Model D synthesiser.

There is a three channel input mixer and a nice large filter cutoff control, along with “1/3” and “2/3” CV inputs to emulate the action of the original VCF keyboard switches, apply 1v/oct to either of these inputs and the VCF keyboard tracking will be the same as the original with Keyboard 1 (1/3) or 2 (2/3) engaged, or use the 1v/oct input to emulate both switches selected. There is a variable Exponential CV input which is about 30% more sensitive than the 1v/oct input, this allows some nice over modulation effects.

We have added Voltage Controlled Resonance (Emphasis) in addition to manual Emphasis control. This uses a vactrol as the control element. The fast vactrol used allows modulation speeds up into the audio range. The filter will of course self resonate and act as a sine wave oscillator too.

There is also an overdrive facility which can be selected with an onboard jumper. This allows the input to the filter core to be substantially overdriven, great for adding a bit of extra dirt to the sound.

Module Width: 14hp
Current Usage: 70ma"

VCA - Amplifier

"The MiniMod Discrete Cascaded VCA is a 10hp wide Eurorack format module. It features two fully discrete transistor VCA cores which are hardwired in series.

There are two audio inputs each with their own level controls along with two CV inputs which control the gain of VCA 1 and a Master CV input and level control which controls the gain of VCA 2. There is also an offset control so that a preset gain can be added to VCA 1. Internally it operates at the same voltage and signal levels as the early Model D voltage controlled amplifier and the output of VCA 1 is hardwired to the input of VCA 2.

A high gain (overdrive) mode can be selected for VCA 1 with an onboard jumper, this overdrives it into soft clipping and in this mode the second VCA can be used in a similar way to the Master volume on a guitar amplifier so that variable levels of distortion (or "grit") can be added to the sound.

Module Width: 10hp
Current Usage: 45ma"

Dual Contour

"Two independant 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.

We have added independant 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).

Module Width: 12hp
Current Usage: 45ma"

Glide Noise

"There is a lot of power and funtion contained within this deceptively small 6hp module. It features both the Glide and the Noise generator circuitry from the vintage Model D synthesiser.

The MiniMod glide uses a discrete dual fet circuit which includes a hold function that can gate the glide effect. Glide is only active when the Hold CV input is high, so if the hold input is connected to the gate output of a Midi/CV convertor then the glide will be active only while the key is actually depressed, emulating the exact behaviour of the original Model D synthesiser.

We have also increased the versatility of the module by adding Glide Up only and Glide Down only modes in addition to the standard Glide Up & Down mode of the original circuit.


The Noise Generator is completely separate from the Glide circuitry. There are three outputs offering White Noise, Pink Noise and Red Noise. The noise source itself is all analogue and uses a specially selected transistor in avalanche mode which is amplified and filtered by discrete transistor based circuitry.

Module Width: 6hp
Current Usage: 45ma"