BACK PANEL
Tuner Output Jack
— The “TUNER OUTPUT” jack is provided to allow a tuner to remain plugged into the amplifi er
while playing. This output remains active when the “MUTE” switch is pressed, allowing for tuning your instrument
while not sending signal to either the “DIRECT OUTPUT” or the speaker. Signal level of -30dB (typical hot bass
level) will drive all known tuners. The front panel jack is in parallel with the rear panel jack allowing for convenient
connection to a rack mount tuner.
Effects Loop Jacks
— The serial “EFFECTS LOOP” jacks are provided to allow access to the signal for the
purpose of inserting signal processing equipment such as compressors, chorus, delay & reverb processors.
Individual pre-EQ loops are provided for the TUBE channel and the FET channel. An additional post EQ loop is
provided for the post-EQ summed (TUBE + FET) signal. This loop may also be used as a preamp output – power
amp input patch point. “SEND” (output) and “RETURN” (input) are n4 dB level. “Series” devices (such as
compressors and gates) require that the signal fl ow out from the send jack on the amplifi er, through the processing
device and back into the return jack on the amplifi er. Parallel or mixed signal devices (such as chorus, delay and
reverbprocessors) require that the signal fl ow out of the send jack on the amplifi er, through the unit where it is split
into a dry (unaltered) signal and a wet (processed) signal. On the processing unit, you will use the mixed signal
output to return the signals (both wet and dry) to the return jack on the amplifi er. The ratio between the wet signal
and the dry signal is heard as the amount of effects added back to the original signal, which is controlled by the
mix knob (also called “balance”) on the effects processor. This may be a real knob (as in the Alesis® Microverb), or
software controlled (as in the Yamaha SPX-90, SPX900 or SPX 990). Set the input sensitivity on the effects
processor according to the processor manufacturer’s instructions. An additional “slave output” jack is provided,
and may be used as an auxiliary output to drive a direct box, additional amp, tape deck etc. This output is summed
(TUBE + FET) post - equalization, and pre master volume. The “MUTE” switch will shut all of these outputs down
when engaged.
POWER
FLEX
Switch
— This switch allows optimum matching of the power supply to the speaker load. Similar in
concept to output transformer matching in tube amplifi ers, this feature allows the GBE 750 to drive 2 ohm loads at
maximum effi ciency compared to more traditional designs. Driving 2 ohm speakers with the switch in the 4-8 ohm
position is not recommended as the amp’s monitoring circuitry may reduce the output power to minimize stress on
the amplifi er. Operating the amplifi er with the switch in the 2 ohm position into a 4 or 8 ohm load is not a problem,
and may be benefi cially used to scale the power of the amp down when playing small clubs that offer limited stage
power. An amber “2 ohm” indicator LED is provided on the front panel to confi rm that the 2 ohm
POWER
FLEX
mode
has been selected.
Fan Control
— The GBE 750 is a fan cooled high powered rack mount device. A continuously variable, side panel
mounted fan is utilized, allowing for quiet operation at low output levels, and greater cooling capacity when playing
at high output levels or under high ambient temperature conditions. Be sure not to block the intake or exhaust vents
when mounting your amp. Specifi cally, beware of “gig-bag” type racks that offer no side clearance.
Direct Output
— The GBE 750 includes a studio quality, fully active transformerless balanced, phantom power
protected “DIRECT OUTPUT”. Recessed switches are provided to customize this output to your needs.
With the “PRE/POST” switch in the “PRE” position, the direct output receives its signal directly from the pre-amp
input buffer amplifi er with no tonal modifi cations. This is a pre gain control, pre-EQ output, with the best signal to
noise ratio and the least possible signal coloration. Most recording and sound reinforcement companies will want to
use this position since changes you make to your stage sound will not affect this output.
With the “PRE/POST” switch in the “POST” position, the direct output receives its signal from the summed (TUBE
+ FET) output of the 5 band equalizers, but pre-master volume. This feature allows for additional fl exibility in some
situations.
A “GROUND LIFT” switch is provided which opens pin 1 (shield) on the direct output to prevent ground loops. Use
the position that results in a minimum of noise (hum or buzz).
A “LEVEL” switch provided to allow selection between nominal mic (-30dBu) and line (+4dBu). Generally, the signal
in the “PRE” position will be somewhat lower than in the “POST” position.
Foot Switch
— The GBE 750 is fi tted with a 6 pin DIN jacks for the 5 button footswitch (included). In order for the
footswitch to function correctly, the amplifi er’s front panel switches for these functions must be in the “out” position.
This footswitch is unique to Genz Benz due to the complex nature of it’s functions and must be factory supplied.
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