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EMS Random Voltage Generator

EMS Data Sheet

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The EMS Range of Ancillary Studio Modules EMS Modules are designed not only for use with Synthi synthesisers but with any complex of voltage controlled equipment, of whatever manufacture. They are supplied in handsome afrormosia cases, but can be removed and mounted in standard 19" racks, occupying only 1.7" (44mm) of vertical space. They contain their own mains power unit with a very wide range of stabilisation to cope with poor mains line conditions, being operable at anything from +10% to more than—23% of nominal line voltage. Connections to and from the modules can be made either from the jack sockets on the front panel or via the multi-way socket at the back.


The EMS Random Voltage Generator produces a staircase type of output, the 'steps' of which occur randomly, but whose voltage range and time variance are controllable in the following ways:

Time: The internal clock which decides the mean rate of events can be (a) freerunning and subject only to manual control, (b) inhibited so that the next random voltage depends on a manual push button or an external pulse (equivalent to external clock control); (c) free-running but voltage controlled so that an external voltage influences the mean rate. In this state the device becomes a voltage/time converter.

If the time variance control is at zero, the mean rate is constant (though subject to change of steady rate if influenced by a control voltage). As the time variance control is tuned clockwise, the mean time random variance becomes greater, and when this control is at maximum the rate will randomly vary in a ratio of more than 100:1. The distribution of chances is rectangular, not Gaussian, so that no part of the variance range is particularly favoured.

Voltage: Two voltage outputs are available and separately adjustable, but both are subject to the same time control — i.e. the steps of the staircase occur at the same time from both outputs. At zero, there is no voltage variance at all, and as the setting is increased the variance about the mean voltage (set at the device being controlled) becomes greater, excursions being both positive and negative of the mean voltage. In addition, a trigger pulse is sent whenever a random selection is made, and a lamp on the panel glows at the same time.

The random voltage generator can be used for quasi-melodic purposes, for interesting timbre and other parametric changes, or at high speeds for randomly varying vibrato or tremolo (very near simulation of natural, performed vibrato), or for producing very dense textures of rapidly changing notes. A very versatile instrument, essential for any well-equipped electronic music studio.


Power Supply:
240 or 115VAC 50/60Hz + 10% to —23%

Control Outputs:
+/- 2.5V max. (this excursion can be offset to accommodate non-EMS products).

Trigger Output:

Mean Time Range:
0.2 - 20 events per second.

Time Variance:
Max. approx. 100:1 (at mid-settings of mean rate — limited by possible clock range).

Select Input and Inhibit/Free Run Switch:
+ 5V at select input or manual push button operates and inhibits after one event if switch at INHIBIT. +5V will run clock at mean rate set while present at select input, if switch is to FREE RUN.

Voltage Controlled Mean Input:
0.5V/octave ( = doubling or halving rate) limited by possible clock range.

Electronic Music Studios (London) Limited
277 Putney Bridge Road London SW15 2PT
Telephone 01. 788 3491/2 Telex 92 83 72
New York: Suite 2222 110 East 59 Street NY 10022
Telephone 212 832 3115 Telex 42 40 33
New Address: 1977: C/o Peter Zinovieff, The Priory
Great Milton, Oxford
Telephone 08446-729

Data Sheet (Optically Character Read) from The Terrey Collection Library

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