Coustic GBE 600 Musical Instrument Amplifier User Manual
Contents
1. GENZ BENZ E N C L O S U R E S GBE 8990 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 8 8 28 CE A NARNING AL epee ba etre Toren or tee GBE 600 BACK PANEL TECHNICAL INFORMATION The first stage of the GBE 600 preamp uses a low noise bi fet linear scaling amplifier with a 2 pole low cut point2. 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 GENZ BENZ E N C LO S U R E S 7811 E Pierce St Scottsdale AZ 85257 Ph 480 941 0705 Fax 480 946 2412 www genzbenz com
3. at 23 Hz to prevent excessive speaker cone excursion and intermodulation distortion Addi tional bandwidth roll off is provided at 20 kHz for RFI suppression The variable gain stages are a feed back divider type control one of which is all solid state and the other utilizing a cathode follower tube each providing a maximum gain of about 30 dB On the tube stage variable non linear loading creates a smooth and natural sounding overdrive rich in harmonics These foot switchable and blendable gain stages feed 3 foot switchable user adjustable signal shaping filters and the 5 band active equalizer These EQ filters provide over 12dB of boost and cut with center position flat The output amplifier feeds the master volume control and fully protected power amplifier A low noise differential drive output ampli fier is provided for the direct output switchable pre post eq and ground lift and is phantom power pro tected The power section consists of a low distortion bipolar power amplifier with integrated limiter which allows gradual overload without sudden loss of feedback control of the speakers The output is rated at 275 watts RMS at 8 ohms 425 watts RMS at 4 ohms and 625 watts RMS at 2 ohms The amplifier topology is low feedback class A B with servo control of bias and DC offset Also provided is on board output limiting dual slope integrated VI limiting solid state thermal protection short circuit load protection dc fault protection and R
4. magnetic pickup consists basically of a permanent magnet or one for each string called a pole piece with a wound wire coil around it As the string interrupts the magnetic field the coil picks up the changes or disturbances in the magnetic field and translates these changes into a small electrical signal This is the same principal as the large electrical generator used by your utility company to power your rig on stage In order to develop a strong enough signal to drive an amplifier the number of windings on the coil s must be very large Additionally in order to keep the efficiency of the pickup high the dimensions of the wire coil must be small and the magnet flux density kept very high thus a small diameter wire is used The end result is a signal that has significant output impedance due to the size and length of the wire used in the pickup s windings A passive piezo ceramic or piezo film pickup is made of a piezo ceramic crystal or distorted Kynar film When this material is moved by the vibration of instrument s body the resulting strain on the crystal or film is converted to voltage via the piezo electric effect The output impedance of a piezo type pickup is typically higher than the magnetic pickup The input impedance of the amplifiers passive input is set high enough to prevent interaction with the high output impedance of all commonly used passive pickups including magnetic piezo ceramic and piezo film types With t
5. 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
6. FI suppression All amplifier status points are indi cated on a dual color led array This amplifier uses heavy duty copper based bi polar power transistors directly mounted to a 2 speed fan cooled extruded aluminum heatsink tunnel The output section sports a combined rating of 1600 watts and 128 amps to insure a conservative and reliable design An important and not commonly discussed specification is the power amplifier s ability to deliver rated power into a reactive load All speakers present a reactive load to the amplifier reducing real world driv ing ability The power section of the GBE 600 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 Genz Benz amplifiers sound so big FEATURES The following feature set is included on the GBE 600 Bass Amplifier These features were developed based on usability and are the result of input from veteran players from around the country It is impor tant for an amplifier to reflect the real needs of the players using them We feel that this amplifier does just that Input The 4 input has switchable sensitivity With the switch in the passive position the preamp pre sents a higher gain and input impedance which is tailored to the characteristics of passive pickups Two distinct types of passive pickup exist there are some exceptions which aren t important for this discus sion A passive
7. d by the optional 4 button footswitch Input Gain Controls amp 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 resp
8. 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 no
9. he 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 controlle
10. ing 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 e The power LED indicates that the amplifier is on and the low voltage regulated power supplies are active e 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 e 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 am
11. onse 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 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 s
12. plifier 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 e The signal LED indicates that the power amplifier is receiving signal over several watts output and all is well e 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 e 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 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
13. t block air flow over heat sinks at the rear of the unit CAUTIONS e Never set an amplifier on anything that will tip over or collapse under its weight e These amplifiers are capable of producing sound pressure levels that may cause permanent hearing loss e 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
14. witch 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 amp 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 accord
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