D.W. FEARN
VT-7 Compression Amplifier
21
You can run a stereo signal with the switch in the Separate position for an effect. On a stereo
pair such as a piano or other sub-mix stereo source, the image will tend to shift from left to
right as the signal becomes louder in one channel compared to the other. This would be dis-
concerting on a stereo bus, but it could be interesting on individual stereo tracks.
With very fast Attack and/or Release times, low-frequency distortion can often be reduced
significantly using the Link HPF position.
Meter Switch
The VU meter can be switched to read either output (“VU”) or gain reduction
(“GR”). In the VU position, the meter will indicate the actual output level of the VT-7. The
“0” VU mark ind4dBm output
In the “GR” position, the meter indicates the amount of gain reduction (compression), in dB.
With no compression, the meter will rest at the “0” VU mark. As compression increases, the
meter will move more to the left. The meter reading indicates the average amount of com-
pression. The precise calibration of the no-signal 0VU indication may drift slightly as the VT-
7 warms up, and change somewhat over time as various components age. This does not affect
the sound of the VT-7 or the gain reduction range. There is a calibration control to set the
0VU indication but it is not something that a non-technical user should adjust.
The VU meter will always indicate an average amount of level or gain reduction, not the peak
value. This is a true VU meter, and conforms to ASA Standard C16.5-1954. The VT-7 is capa-
ble of a wider range of gain reduction than a standard VU meter can accurately display, so it
is possible that the reading could be fully to the left end of the scale (greater than 20dB). This
will cause no harm to the VT-7, although it is an extreme amount of compression.
Like all true VU meters, the reading is an average and does not indicate the peak level, either
in output nor in gain reduction.
Pilot light
This yellow lamp lights whenever the VT-7 is turned on. The VU meters are also
illuminated.
Rear Panel Controls
Power switch
Primary power is applied to the VT-7 circuits when the rear panel power
switch is in the “on” position (|). This switch is directly below the AC input connector.
Mains voltage selector
This two-position switch is set to the appropriate mains power volt-
age in the location where the VT-7 is used. The only active positions are the “115” and “230”
positions. The “230” volt position will properly accommodate any mains voltage from 220 to
240 volts nominal. See the Maintenance section for instructions on changing the voltage.
When operating in the Link or Link HPF positions, only the left
side (Channel A) controls are operative. The right channel (B)
controls will have no effect on the operation. The only exception
is the Gain control, which will still adjust the level of the B chan-
nel in the Link position.
