VM
PRESET
DC BIAS
+
-
.1
.2
.5
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5
10
0
INPUT
+
-
CLIP
ATTEN
1
STABILIZER
RST
MODE
I/O
THRU
+ OUT
- 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.
