Coustic Musical Instrument Amplifier GBE 600 User Manual

600  
SIX HUNDRED  
GBE  
TECHNICAL MANUAL  
DESIGN PHILOSOPHY  
With many years of experience designing and manufacturing both bass guitar speaker cabinets and am-  
plifiers, it became obvious that there is a large market for a bass amplifier line that reproduces the natu-  
ral tone of the instrument itself, while allowing for personalization of tonal texture.  
As with our speakers, Genz Benz amplifiers strive to maximize your instrument’s natural tone and feeling  
without imparting additional coloration or reducing impact and playability. This results will always be true  
to your instrument’s basic natural qualities and your personal tonal signature.  
The circuit design, features and physical construction have been carefully calculated to give you, the ex-  
perienced player, the best performance and value in bass guitar amplification. Featuring sturdy jacks and  
controls, 12AX7 TUBE and solid state FET front end pre-amps, foot switchable channels and shaping  
filters, 5 band active eq, a balanced direct output and an industrial duty bipolar power amplifier with tor-  
oidal power transformer, the Genz Benz GBE-600 bass amplifier gives you the tools and versatility nec-  
essary to sound your very best on stage.  
GBE-600 FRONT PANEL  
GBE-600 BACK PANEL  
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With the switch in the active position, the preamp presents a lower gain and input impedance which is  
tailored to active pickups. An active pickup is, for all practical discussions, any pickup that uses pre-  
amplification between the pickup element and the amplifier input. The purpose of this pre-amplifier is to  
buffer the high impedance signal from the pickup element (magnetic, piezo-ceramic, piezo-film etc) and  
convert it to a higher level, lower impedance form. It is common for a bass with active pickups to have  
higher output level and longer sustain because only a small portion of the energy required to make the  
electrical signal comes from the vibrating string. The majority of the energy comes from an external  
power source such as a battery. Additional features may be provided with the active pickup, such as  
equalization, volume control and compression.  
Input Signal Mute Switch — The input on the GBE-600 bass amplifier includes an “input mute”  
switch. With this switch, you can place the amplifier (and the direct output) in standby mode between  
sets without having to change any of your volume settings. This feature is especially handy during the  
set when using the tuner output since you will still be able to use your tuner without having sound come  
from the amplifier or P.A. system. No more re-patching or fumbling in the dark! A red LED turns on when  
the input mute is active, reminding you that you are in “stand-by” mode. This feature is also controlled by  
the optional 4 button footswitch.  
Input Gain Controls & O/L LEDs The “input gain” controls, in conjunction with the signal and clip  
LEDs, allow you to adjust the preamp input gain sensitivities to the instrument you are playing. Basses  
can have an output level from a few thousandths of a volt to several volts. Generally, you want to see  
only an occasional flash of the red clip LED when you really hit the string hard, then adjust the master  
volume control for playing volume. Distortion of the preamp gain stage will occur when the red clip LED  
is illuminated, so plan accordingly. The best signal to noise ratio will result with the above method. Set-  
ting your playing volume will be a combination of the FET gain control” (FET channel), “TUBE gain con-  
trol” and “TUBE volume control” (TUBE CHANNEL) and the master volume control”, depending in part  
on individual preference. Intentional overloading of the tube channel may be desirable and the O/L LED  
indicates that you are operating the tube preamp stage in the overdrive mode. The FET and TUBE pre-  
amps are switchable and mixable. These features are also controlled by the optional 2 button footswitch.  
Both CHANNEL O/L LEDS are active at all times monitoring each channel’s audio level, independent of  
channel switch position.  
Signal Shaping Switches and Controls — There are 3 separate shaping filters on the GBE-600. The  
“L.F. EXTEND” lowers the low frequency roll-off response of the preamp (between 30 and 45 Hz) to al-  
low the full effect of 5+ string and extended scale instruments. The amount of extension is adjustable  
depending on the setting of the corresponding control. Use this function with care due to the power of  
this amplifier. The “MID SCOOP” function introduces a midrange scoop at approximately 800 Hz, with a  
lower “Q” than typical equalization provides. The amount of scoop is adjustable with the corresponding  
control. The “H.F. ATTACK” function increases brightness and sparkle (approximately 4KHz) of the sig-  
nal, allowing exaggeration of percussive effects and string sound. The amount of attack is adjustable  
with the corresponding control. All 3 filters are footswitchable by the optional 4 button footswitch.  
Active 5 Band Equalization — The “active 5 band equalization” used in the GBE-600 amplifiers is  
composed of 1 shelving low frequency control, 3 peaking midrange controls and 1 shelving high fre-  
quency control. These filters are not interactive and are effective as an advanced tone control system.  
The filters have a cut/boost range of +/- 12dB and a smooth, musical sounding response.  
Low Frequency - 80 Hz  
Low-Mid Frequency - 200 Hz  
Mid Frequency – 500 Hz  
High-Mid Frequency – 1250 Hz  
High Frequency - 4000 Hz  
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Tuner Output Jack — The “tuner output jack” is provided to allow a tuner to remain plugged into the  
amplifier 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.  
Effects Insert Jacks — The “effects insert jacks” are provided to allow access to the pre-equalization  
signal for the purpose of inserting signal processing equipment such as compressors, chorus, delay &  
reverb processors. “Send” (output) and “return” (input) are nominal +4 dB level. “Series” devices (such  
as compressors and gates) require that the signal flow out from the send jack on the amplifier, through  
the processing device and back into the return jack on the amplifier. Parallel or mixed signal devices  
(such as chorus, delay and reverb processors) require that the signal flow out of the send jack on the  
amplifier, 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 amplifier. 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. The “effects send jack” may also be used as an auxiliary  
output to drive a direct box, tape deck etc. This output is pre-equalization, and pre master volume. The  
mute switch” will shut this output down when engaged.  
Master Volume — The “master volume control” is post-eq, and adjusts the signal level sent to the  
power amplifier. Best results are usually obtained when this control is set between the 9 o’clock and 3  
o’clock position.  
Master Section Status Indicators —  
·
The “power LED” indicates that the amplifier is on and the low voltage regulated power supplies are  
active.  
·
The “protect LED” indicates that the amplifier is in “protect” mode and the output relay is de-  
energized. This LED will illuminate for approximately 3 seconds during power switch-on and switch-  
off. It is normal for this LED to glow while continuing to monitor the internal conditions for about 3  
seconds after the protection relay has closed. It will also illuminate during any internal fault condi-  
tion. If this happens, turn the amp off and consult a repair technician.  
·
The “thermal LED” indicates that the amplifier has overheated, engaged the protection circuit and  
shut down. This circuit is self-resetting when the offending condition (blocked air vents, foreign body  
stuck in fan, etc) is corrected. This LED will also flash for a brief time at turn-on and turn-off, indicat-  
ing that the amplifier protection circuits are operating. An additional feature of this LED is that it will  
illuminate about 15 degrees F. before amplifier shut-down, as a reminder that the fan should be in  
the high speed position for this type of extended high power operation.  
·
·
·
The “signal LED” indicates that the power amplifier is receiving signal (over several watts output)  
and all is well!  
The “limit LED” indicates that the power amplifier has reached maximum power and the limiter  
threshold has been crossed. Driving 6dB beyond this point, the amplifier will gradually begin to clip.  
The “output limit switch” engages or bypasses the internal soft clip limiter. This limiter allows simula-  
tion of output saturation as the amplifier nears its maximum power. The limiting action is particularly  
musical sounding, even when driven hard.  
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Fan Switch — The GBE-600 is a fan cooled high powered rack mount device. A 2 speed rear panel  
mounted “fan switch” is provided to allow the reduction of fan speed and corresponding fan noise during  
recording and low power playing. Operating the fan at high speed is recommended anytime the amplifier  
is driving 2 ohms, 4 ohms at high levels, high ambient temperatures and when the “thermal” LED illumi-  
nates, indicating a reduction of thermal headroom.  
Direct Output — The GBE-600 includes a studio quality, fully active transformerless balanced “direct  
output, with “pre-post equalization switch”.  
With the “pre/post switch” in the “pre” position, the direct output receives its signal directly from the pre-  
amp input buffer amplifier with no tonal modifications. This is a pre gain control, pre eq output, with the  
best signal to noise ratio. Most recording and sound reinforcement companies will want to use this posi-  
tion 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 output of  
the 5 band equalizer. This feature allows for additional flexibility in some situations, but is often not de-  
sired for recording or live sound reinforcement.  
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.  
The output level is nominal line level (adjustable between -50 and -10 dB), pin 2 hot. This output is fully  
protected from the effects of phantom power provided by the mixing console and does not require phan-  
tom power to operate.  
Output Jacks The GBE-600 features 2 standard 1/4” speaker jacks plus 2 Neutrik ™“Speakon” NL-4  
connectors. Minimum recommended total load impedance is 2 ohms provided adequate ventilation for  
the heatsink area is provided. The “Speakon” is wired using pins 1+ and 1-, pins 2+ and 2- are not con-  
nected.  
Foot Switches — The GBE-600 is fitted with jacks for 2 different types of footswitch. The 2 button foot-  
switch controls “channel switch” and “channel mix” functions. Any standard latching 2 button footswitch  
with TIP-RING-SLEEVE connector will work, provided there are no LEDs in the switching path. The 4  
button footswitch uses a 5 pin “DIN” connector and controls the “mute” and “shape filters”. This foot-  
switch is unique to Genz Benz due to the complex nature of the functions and must be factory supplied.  
GENERAL SAFETY INFORMAT ION  
Power is supplied to the amplifier through an IEC type detachable cord set with a mains connector, fuse  
holder and internationally rated 115/230 Volts - 50/60 Hz toroidal power transformer. For our interna-  
tional touring players, an external mains line voltage switch is provided, with a fuse size chart printed on  
the rear of the unit denoting the power supply configuration and fuse size that the unit has been rated  
for. International IEC type cord-sets are available for a variety of international power supply sockets.  
The main’s fuse (and a spare) is located in a slid-out drawer in the bottom half of the IEC connector.  
Common sense (as well as the law) dictates that you do not operate the unit where it will be exposed to  
moisture or rain, excessive ambient heat (over 115 degrees F / 40 degrees C) or without a properly  
grounded A.C. power source. Never remove the ground pin from the A.C. power connector.  
Ventilation is required to keep this amplifier from overheating. Do not block air flow over heat-sinks at  
the rear of the unit.  
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CAUTIONS  
·
·
Never set an amplifier on anything that will tip over or collapse under its weight.  
These amplifiers are capable of producing sound pressure levels that may cause permanent hearing  
loss.  
·
There are no user serviceable parts inside these units. Always consult a qualified service repair fa-  
cility for service. THE HEATSINK MAY BECOME VERY HOT!!! WARNING!! DO NOT TOUCH  
The use and operation of this device constitutes an agreement of full release of any and all liability con-  
nected with its use. Only persons familiar with the operation of high-powered audio equipment should  
attempt to operate this device. In addition, by the use of this device, user agrees to hold both GENZ  
BENZ ENCLOSURES, INC and its designers, sales agents and all other affiliates and related parties  
harmless in the event of any accident, injury, damage or loss resulting from such use. Manufacturer’s  
sole responsibility is to provide a warranty on the specified performance of the product under normal  
conditions for a period of 3 years.  
THREE YEAR LIMITED WARRANTY  
TRANSFERABLE  
Genz Benz Enclosures warrants the GBE 600 speaker enclosures and electronics to be free from de-  
fects in materials and workmanship, for a period of 3 years from the date of purchase, when purchased  
from an authorized Genz Benz dealer.  
This warranty does not cover wear and tear incurred from the normal designed use of the product.  
This warranty is only effective if a copy of the original sales receipt is presented at the time of warranty  
service.  
This limited warranty is completely transferable to any subsequent buyer as long as the original sales  
receipt is transferred to such subsequent buyer. See your warranty card for all details.  
ALL WARRANTY SERVICE MUST BE PERFORMED BY A GENZ BENZ AUTHORIZED SERVICE  
CENTER. Before returning any unit to the manufacturer for service, a RETURN MERCHANDISE AU-  
THORIZATION (RA#) must be obtained by calling 480-941-0705.  
7811 E. Pierce St. Scottsdale, AZ 85257  
Ph: 480-941-0705 Fax: 480-946-2412  
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