Allen&Heath GR05 - Manual (Page 13)

GR05 User Guide 13
Input Connector
Plug in a standard microphone cable. Always use good
quality 2-core screened cable. Use a 3-pin male XLR
plug at the
GR05 input.
Pin 1 = 0V ground (screen)
Pin 2 = Signal + (cold)
Pin 3 = Signal – (cold)
For unbalanced line level sources connected with 2-wire
cable link Pin 3 to Pin 1 in the XLR plug.
If you have problems with ground loop induced audible
hum and buzz then first check that each piece of
equipment has its own separate path to ground. If that
is the case then operate ground lift switches on
connected equipment in accordance with the instruction
manuals. Alternatively disconnect the cable screen at
the
GR05 input. Do not remove the GR05 mains earth
connection.
Gain Trim
Adjust the rear panel gain trimmer for nominal 0dB meter
reading on normal microphone speech or source signal.
This is indicated by the front panel meter LED flashing
between green and yellow. If the meter flashes red
(peak) then back off the trimmer or select the attenuator
pad.
Once adjusted the gain trim knob can be removed for
preset control or locked out by fitting the hole plug.
30dB Attenuator Pad
Set the two links as shown to the PAD IN position for
high level input signals. Re-adjust the gain trim if
necessary.
Phantom Power and Lo-cut Filter
For microphones that require phantom power set the
PHANTOM POWER link to ON as shown. This feeds
+15V DC via the signal + and – cables to the
microphone. Most powered microphones will operate at
this voltage. If you are using a studio type microphone
that requires more than +15V then connect an external
phantom power unit available from your microphone
supplier.
To avoid damage to the microphone always use
balanced cables when using phantom power. No
harm will be done to non powered balanced
microphones if phantom power is selected as long as
balanced connections are used.
Selecting the LO-CUT FILTER attenuates frequencies
below 200Hz to reduce microphone handling noise,
desk noise, proximity popping and other low frequency
interference. This is advisable when connecting paging
and announcement microphones. To select the filter set
the link to IN as shown.
Equaliser
There are 3 trimmers for each microphone input. Set to
the mid position the frequency response is flat.
Adjusting the controls clockwise boosts while
anticlockwise cuts the selected frequencies.
The two left hand controls affect the mid to high
frequencies providing a bell shaped response centred
on the frequency which can be selected between 300Hz
and 6kHz. Use this to tune out problem resonances
associated with the microphone and room acoustics.
You can also boost selected frequencies to enhance the
clarity of speech, especially in difficult acoustic
environments such as a swimming pool or sports hall.
The right hand control affects the low frequencies with a
shelving response. Although the shelf peaks at 70Hz
frequencies up to 600Hz can be affected. Use this in
conjunction with the lo-cut filter to tailor the low end
response.
We recommend you experiment with the EQ to achieve
the best result for the application. For example, while
you may wish to adjust for quality full frequency
reproduction of speech in a conference room, a brighter
bass cut sound may be more appropriate in a noisy
meeting hall.
Routing
Each input can be routed to any combination of outputs
via two signal paths. Routed through the VCA path the
signal is affected by the output level controls and
ducking if selected. Routed DIRECT the signal is not
affected by output level control or ducking.
Route via the DIRECT path for priority sources such as
announcement microphones or where the source is to
duck other signals such as paging overriding
background music. Any source which is part of an
alarm or evacuation announcement system should be
routed DIRECT.
Note that sources routed DIRECT do not have to cause
ducking. Ducking is assigned separately.
Make sure that each routing link is correctly fitted. If
routing to a particular output is not required then set the
link to the OFF position as shown.
Routing Examples
Example 1 shows the input routed to all 4 outputs via
DIRECT. This is typical of a paging microphone which
would also be set to cause ducking. Paging
announcements would be heard in all zones.
Example 2 shows the input routed to outputs 1 and 2 but
not to 3 and 4. An example is a local announcement
microphone in the dining area. Here the
announcements would be heard in the dining area itself
and the nearby waiting area or bar. The announcements
would not be heard in the reception area or corridors.