GMS714 Quad VCA

Switchable LOG/LIN Response

The GMS-714 Quad Voltage Controlled Amplifier/Gate contains four high quality VCA devices in a 1MU panel. Each amplifier can be used with an external control input to produce a change in amplifer gain from infinite attenuation to a gain factor of 1. The control curve can be set for a linear or logarithmic response to the input control voltage. Normalization of inputs, reversible attenuators on control inputs, and a built-in output mixer permit various stereo panning tasks to be performed.     


The module contains four seperate high quality voltage controlled amplifier channels. Each channel has an associated control voltage input that passes through a reversible attenuator. The attenuator allows the control voltage to be prescaled from zero up to twice the applied level. When the attenuator control is positioned to the left of 0, a greater negative voltage on the control input will produce higher gain values approaching a gain of 1 in the associated amplifier channel.

The control voltage response curve is determined by a switch on the attenuator knob. When the knob is in, the response curve has a linear action. When the attenuator knob is pulled out, the response curve has a logarithmic action. This response is similar to the logarithmic taper on a normal volume control.


Input normalization and an output mixer allow for the use of the module as a mono or stereo voltage-controlled panner. Channel 1 and 3 are mixed and output on the left mixer output. Channel 2 and 4 are mixed and output on the right mixer output if a plug is inserted in the left mixer output. If no plug is inserted there, the right mixer jack provides the outputs of all four channels mixed together.

The channel 1 input is normalled to channel 2 and the channel 3 input is normalled to channel 4. The control input for channel 1 is normalled to the control input of channel 2 and the control input for channel 3 is normalled to the control input of channel 4. By adjusting the control attenuator for channel 1 to a positive value and the control attenuator for channel 2 to a negative value, a signal fed to channel 1 input will be panned between the left and right mixer outputs if a bipolar waveform is fed to the channel 1 control input.

The pan law can be set for constant voltage by leaving the amplifiers set in a linear control response and constant power by setting both to logarithmic response. Two monaural signals may be panned in this fashion or one pair of stereo input signals can be panned to the pair of mixer outputs using one module. 


Technical Specifications

Each Channel

Input Range
-5 to +5 Volts - AC or DC

Output Range
-10 to +10 Volts - AC or DC

Control Range
-10 to +10 Volts

Module Power
+15 Volts 25 mA.
-15 Volts 25 mA.
+5 Volts 1 mA.

Module Size
Panel height - 8.75 inches (222 mm)
Panel width - 2.125 inches (54 mm)
Depth (behind panel) 3.25 inches (83 mm)



We produce electronic synthesizer modules in the two most popular formats, MU (Moog compatible 5U) and EU (Eurorack compatible 3U). A wide range of voltage controlled modules including oscillators, amplifiers, mixers, envelope generators, special effects units, wave generators, filters, power systems and cases allow users complete freedom to configure any desired electronic music instrument.


Grove Audio builds microphones, preamplifiers, equalizers, compressors and other professional audio equipment for performance and studio use. We build units in popular formats such as 19 inch rack mount and 500 series 3U modules. We can also produce custom designs on request. Contact us for a consultation.


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Grove Audio has been manufacturing professional recording and modularized electronics for musicians and performers since 1995.