AJH Synth MiniMod User Manual

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Glide + Noise User Guide

Thank you for purchasing the AJH Synth MiniMod Glide, Hold & Noise module ,which like all AJH
Synth Modules, has been designed and handbuilt in the UK from the very highest quality compo­nents. We hope that it will help and inspire you towards creating some great music and sound­scapes!

The MiniMod Glide, Hold & Noise module brings the keyboard glide and random noise genera­tion circuitry of the legendary Model D synthesiser to Eurorack Modular format, and also adds
considerable extra functionality.

The Glide circuitry uses a discrete transistor dierential amplier, followed by a dual fet transistor
sample and hold circuit that has the ability to gate the glide eect. 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 a key is actually depressed, emulating the exact behaviour
of the original Model D synthesiser. With the glide control turned to zero it can also be used as a
sample and hold module for voltages in the range 0 to +6 Volts.

We have also increased the versatility of the Glide 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 Random Noise Generator is completely separate from the Glide circuitry. There are three
outputs oering 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 amplied and ltered by discrete
transistor based circuitry.

Module width is 6 HP of Eurorack space and it is compatible with standard Eurorack cases. The
height of the panel is 128.5mm, and depth is 54mm . There are four mounting holes at the
corners of the module and we provide 4 of M3 rack xing screws along with a Eurorack compat­ible power cable. Current consumption is 35mA from the +12V supply rail and 35mA from the

-12V supply rail.

All AJHSynth modules are covered by a one year guarantee against manufacturing defects.

Note:
It is very important that the power supply ribbon cable is connected correctly, see the “adjustment and
calibration” section for an illustration of the correct orientation.

www.ajhsynth.com

7

Glide speed

4

Glide On/O

3

Red Noise Output

1

White Noise Output

2

Pink Noise Output

Controls, Inputs and Outputs

m

GLIDE + NOISE

GLIDE

4

6

2

0

OFF

ON

RED

WHITE

PINK

8

10

UP

DOWN

HOLD

CV IN

CV OUT

Glide Mode

Hold CV Input

Glide CV Input

Glide CV Output

8

6

5

9

1 White Noise Out :

2 Pink Noise Out :

3 Red Noise Out :

4 Glide On/O :

5 Glide CV Input :

This is the White Noise Output and signal level is +/-5 Volts peak to peak. Pure white noise
is a sound that contains every frequency within the audio range (generally from 20 hertz
to 20 kHz) in equal amounts. This white noise is generated by using a specially selected
transistor in avalanche mode and using the exact circuitry from the Model D synthesiser,
so it is a vintage analogue approximation of pure white noise.

This is the Pink Noise Output and signal level is +/-5 Volts peak to peak. Pure pink noise is
white noise that has been ltered to reduce the volume of each increasing octave, which
compensates for the increase in the number of frequencies per octave. Each octave is
reduced by 3 decibels, resulting in a noise signature that has equal energy at every
octave. This pink noise is generated using the same discrete transistor circuitry as the
vintage Model D synthesiser and is an analogue approximation of pure pink noise.

This is the Red Noise Output and signal level is +/-5 Volts peak to peak. Red (or Brownian)
noise is more heavily ltered than pink noise, at the rate of 6db/octave or more, so that it
has a much lower high frequency content. It is most commonly used as a random control
voltage rather than an audio signal.

This switch turns the Glide eect on/o. It is NOT a bypass switch, its function is the same
as turning the Glide Speed control fully counter clockwise.

This is the Control Voltage (CV) Input to the Glide module. The acceptable input voltage
range is +/- 10 Volts. However only positive voltages (0 to +6 Volts) are processed,
negative voltages are ignored and voltages between +6V and +10v are limited to +6v.
The most common application would be to feed in a 1V/Oct signal from a Midi/CV
converter, however it’s use is not limited to this and the module can be used for many
dierent up/down slew eects.