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VM

PRESET

DC BIAS

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INPUT

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CLIP

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STABILIZER

RST

MODE

I/O

THRU

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- OUT

VM!

Control and function reference guide

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SIGNAL PROCESSOR INPUT

Apply signals to be affected by GND CTRL’s signal processor here. The signal processor consists of 
a manual attenuator, 7-preset gain/attenuation stage and DC bias - The signal is processed 
though those stages in respective order. The final output is then sampled by a bipolar LED 
clipping indicator before buffered to a voltmeter, multed normal and single inverted outputs.

7 PRESET GAIN/ATTENUATION

Seven most commonly needed amplitude conversion ratios at your finger tips. Use this control 
to conveniently interface audio and CV within your system. Settings are available to convert any 
level found in audio and video systems to within a needed amplitude range. Use with the DC 
bias control to convert bipolar to unipolar and vice versa. Boost external audio signals too!

MANUAL ATTENUATOR

Use the manual attenuator to add precise control for custom amplitude adjustments. Fully 
clockwise setting is unity and will not affect the presets. Fully counter-clockwise will completely 
mute the signal.

DC BIAS

This control sums a DC signal with the input, after preset gain and attenuator. Center position 
adds 0V DC - effectively adding nothing to the signal. +/-9V DC bias is available via this control.

BIPOLAR CLIPPING INDICATORS

These LEDs, marked “-” and “+” indicate that the signal is about to clip or clipping. The internal 
comparators are set to ~10V and when just barely lit, they indicate your are juuust about to clip. 
When fully lit you are clipping friend! The difference between just clipping and clipping is only 
within 100mV, approximately.

VOLTMETER DISPLAY

Very high contrast OLED meter display. The display has two modes of operation. The default 
mode (shown) produces a virtual analog needle to indicate the amplitude of your signal. At high 
frequencies, the display becomes a bipolar bar indicating the full range of the signal. the hash 
marks represent ~1V per step. The alternate mode is a numerical display. The numerical mode 
indicates the maximum and minimum voltages with floating point numbers accurate to two 
decimal places. While any mode can be used, the default mode is best for quickly viewing AC 
signals or for a pleasing visual appearance. Numerical mode works very well for AC and 
especially well for DC signals. Numerical is the recommended mode for measuring very slow AC 
and all DC signals accurately. See “VOLTMETER TIPS” on the bottom of this page.

STABILIZER

The stabilizer control is an important feature. For some very low and sub audio frequencies, the 
display may appear blank (very low freq) or react erratically with the changing signal (sub 
audio). This may not produce a useful or meaningful voltage indication. The stabilizer reduces 
the speed in which GND CTRL performs updating calculations as you turn the control from fully 
counter clockwise to fully clockwise. This enables very low frequency changes to be perceived 
and additionally causes erratic changes to settle on the maximum and minimum values. The 
default setting for this control is in the fully CCW position. Adjust only as needed or desired.

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TECH SPECS

Width.............8hp

Depth.............25mm

Current Draw

Average..........+45mA

                                  -15mA

Max................+66mA

                                  -15mA

Disp off saves ..+11mA

VM accurate within 20mV

All inputs and outputs DC 

coupled, +/-10V

    Rev Polarity Protected

     RoHS & CE compliant

VOLTMETER TIPS

When using the numeric mode, the MAX and MIN values are displayed as positive and negative respectively. If the signal 
being measured is low frequency like from an LFO for instance, the current position of the voltage (positive or negative) is 
displayed twice, in other words the same reading on MAX and MIN. Similarly, for DC signals the voltage is displayed twice 
and differs slightly between MAX and MIN readouts. For positive DC, use the MAX value and the MIN value for negative DC.

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