Grove Audio GMS-714 User manual

GMS-714 QUAD VOLTAGE CONTROLLED
AMPLIFIER
PRELIMINARY OPERATION MANUAL
11/15/2018
COPYRIGHT 2018 –GROVE AUDIO LLC
ALL RIGHTS RESERVED

Features
4 high quality voltage controlled amplifiers
Linear or logarithmic response switch selectable on each channel
Control voltage input routed through a reversible attenuator
Internal signal routing and switching allows pairs of amplifiers to be used as a stereo
panner
Internal mixer can produce a monaural mix of all four channels or a stereo mix of channel
pairs
Basic Operation
VCA Channel
When the control voltage attenuator knob for a channel is pushed in, the amplifier gain response
to the control voltage signal varies in a linear fashion with respect to the control voltage signal.
When the control voltage attenuator knob is pulled out, the amplifier gain response will vary in a
logarithmic fashion with the control voltage signal. The gain will be approximately X1 with a 5 Volt
input and will have a positive value for voltage inputs greater than 5 Volts.
Plug an input signal into the channel input connector. With no control signal inserted at the control
input, 5 VDC is normalled through the control input jack and fed to the input of the reversible
control voltage attenuator. Varying the control position between 0 and 5 will allow the input signal
to appear on the output jack for the corresponding channel. The signal gain will vary from –
infinity to approximately X1 at the 5 position.
When a control voltage signal is applied to the control input of a channel, the reversible attenuator
will act as a variable gain control with approximately the range of –X1 at –5, X0 at 0, and X1 at
+5.

Internal Mixer
The internal mixer is configured with VCA channels 1 & 3 permanently assigned to the left
channel (marked “MIXED 1 3) and VCA channels 2 & 4 permanently assigned to the right
channel (marked “MIXED (13)24”). If no connector is inserted in the left mixer jack, all channels
are mixed and fed to the right output jack allowing a monaural mix of all four channels.
Panning Function
Pairs of channels can be used to provide a stereo panning function. Channels 1 & 2 form one pair
and channels 3 & 4 form the other pair. To set up for panning operation, place the PAN button for
the channel pair in the ON position. Rotate the odd numbered control attenuator to the +5
position. Rotate the even numbered control attenuator to the –5 position. Push both attenuator
knobs in for linear operation. Apply a bipolar panning signal to the control input of the odd
numbered channel of the pair. The control signal will be processed internally and applied to the
even numbered channels control input to achieve the panning effect.
For a panning control signal that varies between –5 Volts and +5 Volts, the input signal applied to
the odd numbered channel audio input (also internally normalled to the even numbered channel
of the pair) should vary smoothly between the odd numbered channel (left) and the even
numbered channel (right) outputs. When using the mixer outputs, the signal should vary between
the MIXED 1 3, or “left”, channel output and the MIXED (13)24, or “right”, channel output.
If the control signal level goes above the values specified, then the signal will appear to approach
the listener in that channel because the amplifier is actually adding gain only the corresponding
channel above a value of X1.
Mixer Routing Jumpers
Jumpers are provided internally that allow the selection of the source of the signal routed to the
mixer inputs from each VCA channel. One position of the jumper selects the signal before the
output connector and the other position selects the signal after the output connector. The effect of
having the jumper in the second (or “POST”) position is that inserting a connector removes the
corresponding amplifier’s output from the mixer.
Mixer Interconnect
There is a six pin connector that allows multiple GMS-714 module’s mixers to be coupled
together to form a mixes with more than four input sources.
Internal Gate Inputs
There is an internal gate input connector for each channel that will accept a 0 to +5 Volt signal
that is added to the output of CV reversible attenuator before the gain control signal is applied to
the VCA. This input can have various uses including gating the audio on and off for the
corresponding channel or applying an initial gain control signal.