Filter
Top Products
D.W. FEARN
VT-15 Recording Channel
25
should result in “0 VU” on a properly aligned recorder. (This reference level can be changed;
see the Maintenance Section.) This is a true VU meter, and conforms to ASA Standard
C16.5-1954.
In the GR position, the VU meter monitors the amount of gain reduction (compression). As
the VT-15 warms up, the normal “0VU” position of the meter needle (with no compression)
may drift slightly. This has no effect on the sound of the VT-15 nor the accuracy of the gain
reduction measurement.
Power switch and indicator Primary power is applied to the VT-15 circuits when the Power
switch is in the up position. The amber pilot lamp and VU meter back-lighting indicate that
the unit is on. It takes about twenty seconds for the VT-15 to start working, but it is suggest-
ed that you turn on the power at least five minutes prior to use. The tubes are often noisy
until all the internal elements reach a stable operating temperature.
Benc
h Test
If desired, test the VT-15 before installation. The source generator should be set to -50 dBm,
150 ohms impedance, balanced, and the output should feed a balanced bridging input of the
audio analyzer. Measured bandwidth should be 22 cps to 22 kc to obtain the same readings
as the factory test results. Compare your measurements with the test data supplied with VT-
15. Keep the results for comparison in future maintenance tests.
Initial Set-Up
The VT-15 should be installed as detailed in the Installation section. With the outputs con-
nected to an appropriate destination (typically to audio recorder inputs), configure the stu-
dio to monitor the VT-15 output. Apply power and wait about twenty seconds for the tube fil-
aments to get up to temperature. Check for hum, buzz, or other noise. For the first few min-
utes after a cold start it is not unusual for the VT-15 to produce hiss, pops, and microphonic
“clanks” as the internal elements of the tubes expand from the heat. Correct any ground loop
problems before proceeding.
SUGGESTIONS:
You have chosen to use the VT-15 because of the superior sound it provides. To gain the max-
imum benefit from your investment, it is important that you hook up the VT-15 so that other
factors do not adversely affect the sound quality.