PRE420 Instruction Manual – rev. E
Page 8
pin Neutrik™ male XLR connectors with direct
chassis bonding of both pin 1 and the
connector shell. This direct bonding is
important for maximum RF shielding and for
immunity to hum due to shield currents.
All outputs are transformerless and have an
impedance of 60 Ohms balanced or 30 Ohms
unbalanced. All outputs are equipped with
high-performance drivers that can drive high
signal levels into load impedances as low as
300 Ohms without an increase in distortion.
These outputs are well suited for driving long
lines.
•
XLR pin 2 = + Audio Out
•
XLR pin 3 = - Audio Out
•
XLR pin 1 = Cable Shield – bonded to
chassis
•
XLR shell – bonded to chassis
Driving Unbalanced Loads
Special cables are required for driving
unbalanced loads:
•
Connect XLR pin 2 to audio in
•
Connect XLR pin 1 to shield
•
Make no connection to XLR pin 3 – this pin
must be left floating when driving
unbalanced loads
Output Signal Levels
The maximum output level on all balanced
outputs is 29.5 dBu. The four direct outputs
and the two main outputs are equipped with
two-segment LED meters. The green LED
shows signal presence with varying intensity
based on signal level over a range of -8 dBu
to +24 dBu. The green LED reaches half
brightness at an output level of about +4
dBu, and is near full brightness at +24 dBu.
The red LED is factory preset to illuminate at
an output level of pre24 dBu, but may
be adjusted to other levels between 20 dBu
and 29 dBu. The red LED is driven by a peak
detection and stretching circuit so that very
short transients can be observed. The red
LED is a warning indicator; it is not a clip
indicator.
Direct Outputs (1-4)
Each microphone preamp has its own direct
output. Each output has a dual-segment LED
meter.
Control Room Outputs (L&R)
The solo bus is routed post-fader to the
Control Room Outputs. A rear-panel switch
allows these outputs to mute upon headphone
insertion if desired.
Main Outputs (L&R)
The mix bus is routed post fader to the main
outputs. Both outputs have a dual-segment
LED meter.
AC Power Entry Connector
The AC power input uses a standard IEC type
connector and includes a power switch.
Factory-configured 110V units ship with a
power cord. 220V units ship without a power
cord, as they are location-specific and may be
purchased from a local source.
Fuse Holder
The fuse holder is built into a drawer next to
the IEC power connector. The drawer requires
two 5 x 20 mm 250 V Slo-Blo
®
Type fuses.
The drawer includes a voltage selection switch
with two settings: “110” and “220”. Both
settings use a 0.5 Amp fuse.
The AC input has a very wide input voltage
range and can operate over a frequency
range of 50 to 60 Hz. At the “110” setting,
the PRE420 will operate normally over a
range of 105 to 140 VAC. At the “220”
setting, the PRE420 will operate normally
over a range of 200 to 285 VAC.
CAUTION: FOR CONTINUED FIRE
HAZARD PROTECTION ALWAYS REPLACE
THE FUSES WITH THE CORRECT SIZE
AND TYPE (0.5A 250 V SLO-BLO
®
5 X 20
MM – LITTELFUSE® HXP218.500 OR
EQUIVALENT).
