Elby Designs ED102 Octave Volts Hertz CV Processor

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Perfect Circuit Audio (RSS)

"The ED102 is ideal if you want to upgrade your synthesizer by adding on other synthesizer units having different kinds of keyboard control voltage and trigger signals.

The built-in, fully adjustable log amp, anti-log amp, and trigger processor ensure complete system flexibility and compatibility between any presently voltage controlled synthesizer. In order to get the most out of your ED102, please read this owner's manual carefully before use. The ED102 Hz/V/Oct Converter is designed for the purpose of connecting V/Octave synthesizers with Hz/V synthesizers. This sophisticated signal processor greatly enhances the performance possibilities of your synthesizer.

Among presently available music synthesizers, there are two different types of control system used for the VCO (voltage controlled oscillator) and EG (envelope generator). One of these systems is used by Korg and Yamaha; the other is employed by every other synthesizer manufacturer. The ED102 provides you with a way to change the control signals of one system into the control signals used in the other system. In this way, it acts as an interface so that any two synthesizers can be used together, provided that the synthesizers are equipped with the conventional input and output jacks for control
voltage and trigger or gate signals.

CV systems

In the Hz/V system, the VCO oscillator frequency is proportional to the control voltage whilst in the V/Octave systems the oscillator frequency changes one octave for every one volt (1V) change in the control voltage. Since an increase of one octave means that the frequency is doubled, each increase of one volt in the control voltage means a doubling of VCO frequency.

The problem with the V/Octave system is that it must employ a log amp in order to double the frequency for each one volt increase in the control voltage. Log amp circuitry can, unfortunately, be very unstable because of its sensitivity to temperature changes. This causes so many problems that most professional musicians automatically assume that synthesizers always have unstable pitch. When Korg developed their first Korg synthesizer, they decided that such a circuit was entirely unsuitable for a musical instrument. So, instead they invented their own unique, patented circuit in which the keyboard voltage (which is the VCO control voltage) itself doubles for each one octave increase in pitch.

Four Sections

Log Amp: This changes a Hz/V type keyboard CV (control voltage) output into a V/Octave type of CV. Use the Log Amp to change the control signal from a Hz/V synt
hesizer into a signal you can use with a V/OCT synthesizer.

Hz/V input (0 ~ 15V)
Oct/V Output (-12V ~ +12V)
Frequency knob: Bi-polar offset of frequency
Width knob: Bi-polar control of width of the output
Antilog Amp: This changes a V/Octave type of keyboard CV output in to a Hz/V type of CV. Use this Antilog Amp when you want to control a Hz/V synthesizer, such as a Korg, by means of a unit that uses the V/OCT system.

Oct/V input (-4V ~ +4V)
Hz/V output (-12V ~ +12V)
Frequency knob: Bi-polar offset of frequency
Width knob: Bi-polar control of width of the output
Adding Amp: This can be used for mixing control voltage signals or sound signals. When not plugged into an outlet, the adding amp operates as if -5V and +5V inputs were connected to its two channels. Therefore, depending on how you set up your equipment, you can also use the adding amp as a voltage supply, or to shift a control voltage to a higher or lower value, and so forth.

Two inputs each with level knob
Mix output
In 1 normalled to a +5V DC signal
In 2 normalled to a -5V DC signal
Trigger\Gate: This lets you change either type of trigger signals, S-Trig or V-Trig, into the kind of trigger signal you need by means of the Reverse switch.

2 Identical sections featuring:
Input (Vth = +2.5V)
Output (0V ~ +15V)
Reverse Switch
LED Indicator"