TECHNICAL INFORMATION
The first stage of the GBE 1200 preamp uses a low noise BI-FET linear scaling amplifier with a 2 pole low cut point
at 23 Hz to prevent excessive speaker cone excursion and intermodulation distortion. Additional bandwidth roll-off is
provided at 20 KHz for RFI suppression. Additional front end control is provided with the active/passive gain switch,
signal mute switch and pre-mute tuner output jack. The variable gain stages are a feedback-divider type control, one
of which is all solid state and the other utilizing a 12AX7 dual triode tube, each providing a maximum gain of about
30 dB. On the tube stage, variable non-linear loading creates a smooth, musical sounding overdrive rich in
harmonics. These foot-switchable and blendable gain stages feed 3 foot-switchable, user adjustable signal shap-
ing filters, multiple effects loops and the dual 5 band active equalizers. These EQ filters provide over 15dB of boost
and cut, with the center position being flat. The output amplifier feeds the master volume control and fully protected
power amplifier. A low noise differential drive output amplifier is provided for the direct output (switchable level, pre/
post EQ and ground lift) and is phantom power protected.
The power section consists of a low distortion bipolar power amplifier with integrated limiter which allows gradual,
controlled overload without sudden loss of feedback that would result in loss of control of the speakers. The output is
rated at 550 watts RMS at 8 ohms, 1000 watts RMS at 4 ohms, and 1200 watts RMS at 2 ohms, using a burst rating
ten times more stringent than typical industry standards. The amplifier topology is fully symmetrical dual-differential
low feedback class A-B with automatic servo control of bias and DC offset. Additional performance headroom is
gained by matching the power supply to the load impedance using the
POWER
FLEX
impedance selector switch on
the back panel.
Also provided is sophisticated on board dual slope integrated VI output stage protective limiting, unique rail detector
short circuit protection enhancements, solid state thermal protection sensing, short circuit load protection, DC fault
protection and RFI suppression. All amplifier status points are indicated on a dual color LED array. This amplifier
uses heavy duty copper based bi-polar power transistors directly mounted via our “nerf bar” clamping system to a
variable speed fan cooled extruded aluminum heatsink tunnel. It is immediately apparent that this is a serious ampli-
fier, as the output section sports 12 output transistors with a combined rating of 2400 watts and 192 amps to insure a
conservative and reliable design.
An important and not commonly discussed specification is a power amplifier’s ability to deliver it’s rated power into a
reactive or low impedance load without premature engagement of the amp’s protective VI limiting circuitry. All
speakers present a reactive load to the amplifier, reducing real world driving ability. The power section of the GBE
1200 amplifier is rated to deliver full power into a reactive load with a 45 degree (leading or lagging) power factor
phase angle. This is one important reason why all Genz Benz amplifiers sound so big!
FEATURES
The following feature set is included on the GBE 1200 bass amplifier. These features were developed based on
usability and are the result of input from veteran players from around the country. It is important for an amplifier to
reflect the real needs of the players using them. We feel that this amplifier does just that.
FRONT PANEL
Input
— The ¼” instrument Input has switchable sensitivity. With the switch in the passive position, the preamp
presents a higher gain, which is tailored to the characteristics of passive pickups. A passive magnetic pickup
consists basically of a permanent magnet called a pole piece with a wound wire coil around it. The GBE 1200’s input
impedance is set high enough to prevent interaction with the high output impedance of all commonly used passive
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