Glyph GPM-216 - Manual (Page 12)

Glyph GPM-216
12
Test Drive the GPM-216: Inputs and Gain
The universal input connections can accept balanced or unbalanced signals via ¼” or XLR connectors.
Since the GPM-216 has built-in preamps, you can just plug your microphone or guitar cable right into the
universal input. No external preamp, direct box, or mixer is needed.
To use a microphone, plug the microphone’s XLR cable into one of the universal inputs. Whenever an
XLR cable is connected to a universal input, the microphone preamp is enabled and the gain range of the
trim knob is set to range from +10 to +58dB. The input impedance of each microphone preamp is
1.5Kohms. Full-scale input is 9dBu with the trim set to minimum gain.
The GPM-216 can provide 48 volts of phantom power for microphones that require it. Phantom power can
be enabled by going into Setup Mode, or via the Configurator remote software, and the LED on the
faceplate marked +48v will light up. Phantom power will be provided to both microphone inputs.
Phantom power will not be applied to any line level equipment or guitars plugged in using cables with ¼”
connectors.
To use a guitar or line level signal, just plug a cable with a ¼” connector into one of the universal inputs.
Whenever a ¼” cable is connected to a universal input, the guitar/line preamp is enabled and the gain
range of the trim knob is set to range from 0 to +45dB. The guitar/line preamp can support both guitar &
line level signals. The input impedance of each guitar/line preamp is 102Kohms. Full-scale input is 18dBu
with the trim set to minimum gain.
If you want to adjust the input level of a universal input, just turn the trim knob and watch the
corresponding level meter. The red light at the top will light anytime the input signal is greater than –
6.5dBFS (or within 6.5dB of clipping). The yellow light represents a signal greater than –12.5dBFS and the
green light represents a signal greater than –24.5dBFS.
For optimal audio quality, you should adjust the input trim knob so that your loudest input signal lights up
the yellow light, but not the red. When the red meter light shines extra bright, the signal has been clipped.
If the signal level ever exceeds 0dBFS the signal will be “clipped” and you will hear a “pop” or “tick” in the
sound. This is a very bad thing, and clipping should be avoided at all costs! There is enough headroom so
that you can be conservative in this area, and there is no need to push the input levels right up to the edge
of clipping.
Back Panel Details
About Cable Splits, Phantom Power, Mic Preamps
In a typical stage use, microphone signals would connect first to the GPM-216, and would loop out to the
FOH console. This is considered a cable split with the signal being sent to the mic preamp in the GPM-216
and the mic preamp at the FOH console simultaneously. Cable splits are already very common in venues
where the stage mics are sent to the FOH console and the monitor console at the same time.