Crown Audio VT-15 Mic Input, Line Input, Instrument Input, Output

D.W. FEARN

VT-15 Recording Channel

6. Adjust the Eq controls for the desired sound. (Remember to use the Boost and Cut togeth-

er to shape the sound.)

7. Switch the VU meter back to the VU position.

8. Adjust the Gain control for a normal indication. Peaks should rarely go into the red (0VU).

This procedure will provide you with the optimum gain structure in the VT-15. Headroom will

be maximum and noise will be minimum.

After the initial set-up, you can fine-tune the controls for exactly the sound you are looking

for. However, you will rarely have to change the Preamp Amp gain after the initial set-up.

Here is detailed information on the VT-15 controls:

Mic Input

Since the input cable will be carrying very low level audio, it is important that a well-shield-

ed cable is used. There should be no additional connectors, patch jacks, switches, etc.

between the microphone and the VT-15 input. This can be achieved with a dedicated line

from an XLR connector in the studio to each VT-15 in the control room. Although long input

cable runs have little effect on the performance of the VT-15, it is preferable to keep the input

line as short as possible. Avoid locating the VT-15 where it will be subjected to high sound lev-

els or excessive vibration (such as on a drum riser).

The Input connector can also accept a line-level (+4dBm, balanced, 600-ohm nominal) signal. The

front panel “Mic/Line” switch should be in the “Line” position. A line-level signal into the VT-15 while

the unit is set for “Mic” will result in very high level and extreme distortion. Although this will not harm

the VT-15, it could be dangerous to your speakers and your ears! So make sure the switch is set appro-

priately before making the connections.

Many of the other switches are usable while in the “Line” position. The “-20” pad in particular may be

useful if the input signal has a higher-than-normal level. The “150/Lo-Z” and “+48” switches are locked

out in the “Line” position. The “Phase” switch is still active and may be useful.

The “Mic/Inst” switch changes the input source from the read-panel XLR connector to the front panel

one-quarter inch “Inst” input. This jack is used for recording electric instruments such as electric bass,

electric guitar, electronic keyboards, etc. Any device that would normally be plugged into a guitar amp

or DI box will properly match the VT-15 “Inst” input.

The output of the VT-15 is line level, transformer balanced. Note that vacuum tube equip-

ment is more sensitive to load impedance than solid state units. The VT-15 design was opti-

mized for feeding a balanced bridging input (20k ohms or greater). When feeding a 600 ohm

load, there may be a slight degradation of some of the specifications. In modern studio equip-

ment, bridging line inputs are universal. If the device being fed by the VT-15 has an input termi-

nation switch, that switch should be in the “off” position.

The VT-15 can feed balanced or unbalanced inputs with no need for any modification in out-

put wiring. Either pin 2 or 3 can be grounded, although pin 2 is normally used as the ”hot”

and pin 3 grounded in unbalanced configurations.