Allen&Heath PA28 - Manual (Page 18)

18 PA User Guide
The STEREO Channel
Dual Stereo Inputs
Each stereo channel has two
independent stereo inputs, ST1(3) and ST2(4). For
convenience, one uses RCA phono connectors, the other uses
TRS jacks. The two inputs mix together to feed the channel
strip, or ST1(3) can be routed direct to the LR mix instead,
leaving ST2(4) to feed the channel. This provides a very
flexible arrangement for mixing up to four stereo sources.
ST1(3) INPUT
RCA phono inputs for connecting line
level stereo signals. These connectors are popular with
consumer and semi-professional equipment such as tape
deck, video camera, computer, CD and MiniDisc players.
ST2(4) INPUT
TRS jack inputs for connecting line level
stereo signals. The inputs are unbalanced but can also accept
balanced sources. The ring connection grounds the –ve (cold)
signal to unbalance a connected balanced source. Typical
applications include stereo keyboards, voice modules, effects
processors and sub mixers.
☺
Using the stereo channels These inputs are intended
for local stereo sources. The unbalanced connections work
fine with the higher voltage levels and low impedance
associated with such equipment. If you need to connect
equipment further than 10 metres away we recommend you
use the mono channel balanced line inputs or DI boxes feeding
the long cables to the mic inputs.
ST1(3) Mode Switch
This small switch is recessed to
prevent accidental operation once it is set. In its up position it
is flush with the panel and mixes the ST1(3) signal with ST2(4)
to feed the stereo channel. Use a pen or similar pointed object
to press the switch if you want to route the ST1(3) signal direct
to the LR mix instead of the stereo channel.
☺
Mixing two stereo signals into the channel (Switch
flush with panel). There are many situations where it is
convenient to combine two sources into one channel. For
example, you may have two MiniDisc players being used for
backing tracks or sound effects, a stereo keyboard together
with additional MIDI controlled voice module, two effects
processors returning into one effects channel, or simply two
unrelated sources being used at different times. Use the two
GAIN controls to adjust the balance between the sources.
☺
Sending ST1(3) direct to LR (Switch pressed, below
panel). Some sources may only require ‘set and forget’ routing
to the main LR mix. For example, an external reverb processor
return with its levels mixed using the channel aux sends, or the
outputs of a stereo sub mixer with local control of its mix.
Routing ST1(3) in this way frees up the stereo channels for
other sources. Adjust the level using the ST1(3) GAIN control
from fully off to +10dB boost.
GAIN
Adjusts the sensitivity of the channel preamp to
match the connected source to the 0dBu operating level of the
console. The control has a range from fully off to +10dB boost
so that sources from -10dBu and higher can be connected.
☺
Setting the gain Use the channel PFL function to view
the signal level on the console meters. Adjust the gain control
for average signal level around meter ‘0’ with loudest peaks no
more that ‘+6’. If you see the channel PEAK indicator flash
back the gain off a little.
5
0
LR
10
11-12
-20
-30
OO
-10
10
0
5
O
-20
-30
O
-10
R
ST2/4
L
GAIN
L
ST1/3
R
LR
GAIN
CHAN
STEREO CHANNEL +
SUM
TO LR