7
The
Power
switch, on the rear, is used to turn on power from the battery or external power supply.
Turning this switch off disables these two power sources but if the USB bus is still active then the
USB Dual Pre
will be powered by the USB bus alone and the red power LED will still light to indicate
that USB power from your computer is still on. When the switch is in the on position and all three
power sources are available, the USB interface will be powered by the USB bus but the preamp and
phantom power sections will draw their power from the external AC power source or from the battery
if an external source is not available. Normally in a desktop, studio, or home recording setting the
power modes would not be an issue. When used in a portable or remote recording situation the
USB
Dual Pre
, a laptop computer, a pair of microphones, and a set of headphones, become your entire
system. In this setting you can either power everything from your laptop or if you have a 9 Volt battery
installed and the Power switch is on, power to the preamp and phantom powering sections will come
from the battery and the laptop will only be powering the USB interface. This helps to maximize your
remote recording time.
LED metering circuitry on each channel aids in setting gain and has a fast attack to help indicate any
clipping. The metering is located in the signal chain just after the preamp circuitry to help in setting
signal levels going to your computer. The Monitor controls come after the metering so that you can
use the meters to set the overall input gain on each channel for best recording dynamic range and
then trim the Monitor Mix and Level to the monitor system you are driving. The red “Clip” LED comes
on just before clipping (2dB before digital clipping and 6 dB before analog clipping) and should light
on musical peaks only. The green “Signal” LED comes on around 10dB before the “Clip” LED and
indicates how far below clipping your signal is. The “Signal” LED has a longer release time and
should be on much of the time during performance and if not it indicates that your signal or input gain
may be too low for best results.
A brief note from customer service:
Once in a while a customer will call and say: I think my ART preamp is "noisy". What's wrong?
If you experience unwanted "noise" in your system when you use a stand-alone preamp, please
consider what your signal is and where you're sending it. Some people send the signal from their
preamp to a mic input (they figure, "well, I'm using a mic!") on the board or recorder. This is in fact
incorrect and could create higher overall noise. ART preamps are actually intended to output a nice
fat LINE LEVEL signal. If you send that line level signal to a recorder or mixer's Mic input, that circuit
will usually add more gain to the signal. Gain on top of gain will indeed result in noise. Please treat
the output signal as line level and you'll be pleasantly surprised at your new clean and warm sound.
The same rule applies for guitar and bass players that use ART preamps as their front end. Send the
signal from your preamp to a low gain input on your amp, or even a "loop return" jack which allows
you to bypass the amp's solid state preamp altogether.