Frequently Asked Questions

Yes, it works on the same signal levels and system voltages. It has a Eurorack compatible power bus connector and front panel sizes and hole spacings are also compatible.

It is possible to fit 108hp of our AJHSynth modules into the KB37 (not ideal, but possible) and here's how we do it - the sheet metal front panel that surrounds the Eurorack frame on the KB37 is quite thin and we found that you can just fly the last module over by 1HP so that part of the module front panel (the underside) is actually sitting on top of the right hand side front panel of the KB37, it tilts the last module right side edge up slightly but you have to look fairly closely to see this. This means that the last module sits at a very slight angle rather than parallel to the front panel of the KB37. Therefore, the edge of the right hand side module front panel will project upwards by around 1mm. It is not necessary to modify the KB37 or any of our modules to achieve this, so no damage is done in the process.

If you prefer all of the modules to look level then this is possible too but a little trickier - you would fit a couple of extra washers on the back side of every fixing screw on all of the modules, between the back of the front panel and the frame, and this will lift up all of the modules so that they then all sit evenly above the KB37 front panel.

For best performance we would strongly recommend a linear (rather than DC/DC switched mode) Eurorack power supply. Hinton Instruments and Doepfer power supplies have been proved to work very well, however there are other linear and some switched mode power supplies that are equally suitable. Some (but not all) of the currently available DC/DC converter based Eurorack power supplies can inject quite large levels of switching ripple and noise (up to 200mV!) onto the power rails, this may cause audio problems and instability with analogue modules such as ours which use low internal signal levels.

It is also good practice not to mix digital and analogue modules on the same power buss bar.

Voltage controlled cross fading from LP-NOTCH-HP is very easy to do on the Gemini 2412 by using both filters in parallel mode and taking the output from D- OUT (Dual Mixed Output) on the central mixing section. The manual LP-NOTCH-HP control on the individual GEMINI 2412 filters is simply a manual cross-fader which acts as a mixer between the HP and LP filter outputs. Mixing together the HP and LP outputs in this way gives a notch filtering effect towards the centre position, where we have an equal mix of LP and HP filtering.

We can reproduce this exactly by mixing together VCF1 & VCF2 from the Gemini 2412 in Parallel mode as follows:

Send the same input into both filters - this doesn't even need a spit patch cable or multi, the VCF 1 input is normalised to VCF2 input by default so we only need to feed the input into IN 1 on VCF1.

With the mode switches set VCF1 to LP and VCF2 to HP.

Set the filter interconnection switch to Parallel mode

Adjust the frequency and resonance to the same levels on VCF1 and VCF2.

Take the output from the D-OUT jack - this is the mixed output from VCF1 & VCF2.

Set the Audio Mix control to the VCF2 position

Patch a unipolar control voltage from an LFO to the MIX CV input. This control voltage will cross fade between VCF1 and VCF2

This configuration allows much more control that we would have by simple manual cross-fading using the front panel LP-Notch-HP control, here's some of the extra possibilities:

We can control the cut-off of both filters simultaneously by patching a CV to the D-FCV input, however in addition, the amount of filter frequency CV sent to each filter can be varied with the D-FCV Mix control. We can vary the Resonance independently for VCF1 & VCF2, they do not both have to have the same resonance level, and here we can voltage control Resonance independently for the LP and HP filters. We can set different levels for VCF 1 and VCF 2 (with the IN 1 and IN 2 level controls) and we can also invert the output of VCF2 against VCF1, which will give a different effect due to phase cancellations. We are not limited to using an LFO for cross fading, any CV source can be made to work - so you could use an envelope generator, a sequencer or the CV out from a keyboard.

In addition to +12v, -12v and +5v rails the Eurorack power supply bus has extra connectors to distribute CV and gate signals. If you attach a compatible Midi/CV converter to this bus then (usually by default) it will output it's 1 V/oct and gate signals to this bus, which can then be accessed by other modules as they are distributed in the same way as the +12v, -12v and +5v supplies.

This handy feature allows us to cut down on patch cables, for example the Glide Noise module can be configured to feed its output (which is a 1V/Oct pitch CV) directly to three VCO's via the CV bus, so this saves three patch cables. This is done through normalising on the 1V/Oct input jack sockets on the MiniMod VCO itself, if a patch cable is plugged into the VCO 1V/Oct input then the pitch CV from the distribution bus is disconnected and the pitch CV is taken from the patch cable instead.

A Gate signal can also be fed to the distribution bus from the output of a Midi to CV module or sequencer (assuming that they have implemented this feature) and this would connect directly to the Gate input of the Dual Contour or DH-ADSR envelope modules, so that another one or two patch cables are saved. The Gate inputs of these envelope modules are normalised in the same way as described above for the VCO, but obviously this is a different signal type.

The WaveSwarm is not designed or intended to be used without an input signal, it will produce a cracking noise from the output in this configuration as the animators are looking for a signal to latch to, and as there is no signal present they will just trigger off the noise floor and create a rather unpleasant crackling and clicking noise on the output. The solution is to ensure that a Waveform is always patched to the input when you wish to use the module. See the "Getting the best from your WaveSwarm" section on the WaveSwarm product page for more useful hints and tips.

For customers requiring a suitable Midi/CV Converter we strongly recommend the Kenton Modular Solo, it has the essential low note priority mode (in addition to last note and high note priorities), variable retrigger times, a very accurate low drift 16 bit D/A converter and a host of other useful features.

Unfortunately when the Eurorack format was first developed non polarised connectors were chosen for the distribution bus and modules, so it is quite possible to connect the power header the wrong way around and in the process damage a module or the power supply itself by applying a reversed voltage to it or short circuiting it.

We have built protection circuits into the positive and negative rails on all AJHSynth Eurorack modules. It does not use a fuse or a crowbar circuit that can overload the power supply, it is a safe solution that simply prevents the flow of current in the wrong direction and it ensures that no damage is caused to your AJHSynth module should you accidentally connect the power cable the wrong way around.

However, connecting a 16pin header the wrong way around at either the module or power bus end could damage the power supply in your case, as it can short circuit the +12V supply rail to ground. Most power supplies have over current protection to cover this scenario and prevent damage to them, but obviously you would not have any power on the +12V power rail, so non of the modules connected to that power supply will work correctly, as they will have a -12V supply only rather than the dual +/-12V supply that they expect.

In view of this, do be very careful to connect the power cable the right way around on both the module and the distribution bus power connectors, the stripe on the ribbon cable denotes -12v and the cable should be connected so that the stripe lines up with the -12v markers on both the module and the power bus connectors.

The MiniModVCO can be used as an LFO, there is a Lo setting on the octave switch for this and it acts in exactly the same fashion as the Model D VCO 3, except that it does not have the reverse ramp waveform which VCO 3 featured instead of Sharktooth. There wasn't space on the panel to add this feature, but if required this can be easily obtained by passing the sawtooth wave through an inverter, our CV-Mix-VCA module could be used for this purpose.

At low frequencies the MiniMod VCO acts as a VC-LFO rather than a simple LFO, as the frequency can be varied by adding a control voltage to 1v/oct or exp CV inputs, and a negative voltage is accepted. So, if you had lets say 1Hz with 1v applied to the V/oct input, then patching -1v to the 1v/oct input will drop the frequency to 0.25Hz, -2v will take it down to 0.125Hz and so on. It will go pretty low, with -5v to the 1V/Oct input it runs at around 0.02Hz, or one cycle every 50 seconds.

The AJHSynth Precision Voltages module is a useful addition for changing the frequency range of MiniMod VCO's, by using its input and output the internal summing feature allows an exact voltage to be accurately added to the pitch CV, so you can easily switch the frequency range up or down by full notes or octaves.

Yes, all of the modules are 100% analogue, no virtual analogue or digital modelling here!

Yes, the Moog Mother 32 is Eurorack compatible and so MiniMod modules will work with it. However, there is a known issue when using the Mother 32 KB Output with external VCO's - including the MiniMod VCO. Because of the relatively high output impedance (1 Kilo ohm) of the M32 KB output a suitable active buffered multi must be used to correct the impedance missmatch so that tracking problems are not experienced - if connected directly without an active buffer the external VCO will go flat at the rate of 1% per octave, or 2% per octave if two VCO's are attached, assuming that the VCO's have an industry standard 100K input impedance, so with two VCO's attached they would be 120 cents (more than a note) flat over five octaves. The input impedance of the MiniMod VCO is 100K so this applies.

Also, please note that not every active buffered multi will be effective, to obtain correct tracking it is very important that the active buffer has a very high input impedance (ideally 1 Megaohm or higher) and also a very low output impedance (ideally 10 ohms or less). Our V-Scale multi is very effective in this role and it was specifically designed for this purpose. Active multi's from other manufacturers may also work, but only if they meet the above design criteria.

No, they are all handbuilt by ourselves in the UK. We do not use assembly robots or farm out assembly to other companies, instead we paintakingly hand assemble, test and calibrate each module ourselves from high quality components to ensure the very best sonic performance, quality control and customer satisfaction.

The vast majority of components on the MiniMod circuit boards are small SMD devices, which are much more compact than their older through hole equivalents. We only use through hole components when an SMD equivalent is not available or would change and/or compromise the sound.This allows all of the circuitry to be fitted into the much smaller Eurorack module format, this would not be possible with vintage through hole components.

For the transistors themselves we commonly use paired transistor devices to save space, these contain two transistors within a small six pin or eight pin package. These transistors use EXACTLY the same silicon die as their much larger through hole equivalents. In through hole transistors the actual die inside is very small, as can be seen from the illustration below. Most of the transistor package is either empty space or filler resins which have no effect on the electrical characteristics of the transistors themselves.

The main advantage of building the MiniMod into Eurorack format is that it opens up a previously closed system to experimentation, with interesting and sometimes unexpected sonic results.

The MiniMod VCO in particular can produce some quite extreme sounds when using sync or cross modulation, check out some of the video's in the Sounds and Video's section; particularly "VCO Sharktooth Modulation" and "VCO Sync Weirdness"

It is currently available in Eurorack format only, and we do not have any plans to realease it in other Modular or stand alone formats.

Moog S trigger is not supported on the Eurorack synthesiser format as it uses the more common voltage rather than switch based trigger system.

However, an S-Trigger facility can be added at a fairly low cost on the MiniMod and/or other Eurorack modules by using a third party S-Trig to Voltage Trigger adapter.