Specifications

HD I/O Guide26
Using Input Trims
Input Trims
The Input Trims below the two DB–25 connec-
tors on the HD I/O AD Expansion card are used
to store a calibration setting each channel.
These adjustable Input Trims are for precisely
calibrating the adjustable headroom settings for
each channel. You can adjust each Input Trim
by hand with a small screwdriver.
About Input Operating Levels
Check the manufacturer’s documentation for
your mixer, power amplifier, or effects processor
to see if it operates more comfortably at line
level, in which case consider setting the HD I/O
to operate at –10 dBV line levels and adjusting
the Input Trims.
Consider the following when connecting a
mixer:
 If your mixer cannot handle more than 1.5V
(RMS) inputs at +4 dBu, then you should set the
HD I/O to operate at –10 dBV line level.
 If your mixer can handle up to 15.5V (RMS)
inputs, or has pads or attenuators on its inputs,
then you can use the +4 dBu setting on the
HD I/O.
 HD I/O is calibrated at the factory for 18 dB
headroom at the +4 dBu setting.
Most manuals contain device input specifica-
tions, including whether or not there are pads or
attenuators. Refer to the manufacturer’s docu-
mentation for your mixer or power amplifier for
more information.
Input Trims
If you want to switch the input levels of the
HD I/O from +4 dBu to –10 dBV, you can
access these parameters on a channel-by-
channel basis in the Hardware Setup dialog
(see “Hardware Setup” on page 17).