Mesa/Boogie Big Block 750 Stereo Amplifier User Manual
Contents
1. The TREBLE is also an active shelving style control like that found in the BASS and again it was chosen for its ability to radically shape the upper harmonic region Like the BASS it also has a center Q point with harmonics above and below responding in harmony as it is dialed for either cut or boost As the control is increased past 12 00 it produces a 6db per octave rise in gain starting at 723Hz until MESA 20db is reached From this point gain remains constant at 20db for all frequencies above 723Hz all the way out to 20Khz This scheme lends a sweetness of sound while retaining the necessary cut and focus associated with a traditional passive TREBLE control As this control is dialed below 12 00 it begins a 6db per octave cut from 3 2Khz to the shelving point at 723Hz where it continues to aia GY GES attenuate all frequencies above 723Hz until 20db is reached where cut gain remains constant until the control reaches 7 30 off The ability to cut these frequencies more radically makes it possible to C obtain incredibly rich and warm old school R amp B and Jazz sounds that rival any recordings of the day This active shelving TREBLE control completes the rotary tone control string to create a powerful and extremely accurate network to use as your fundamental platform It s no wonder many first time BIG BLOCK 750players make the comment that just these controls com2. PAGE 7 REAR PANEL CONTROLS REAR VIEW Big Block 750 CAUTION Unplug power fu M PULSE BIG BLOCK 750 ii bashing cas POST SIMUL STATE BASS AMPLIFIER TUBE DRIVEN MOSFET POWER EFFECTS 7 SPEAKER lt gt POWER FUSE 15 BLO DIRES esl 1097 TUNER ey ee Cr HANDBUILT IN PETALUMA CALIFORNIA this is the A C Mains Fuse for the BIG BLOCK 750 REPLACE ONLY WITH A SLO BLO TYPE FUSE OF THE PROPER RATING THIS IS EXTREMELY IMPORTANT AS THE BIG BLOCK 750 DRAWS A SUBSTANTIAL AMOUNT OF CUR RENT AT HIGH OUTPUT LEVEL SETTINGS CAUTION Unplug power bal holding chassis FUSE rating for USA 15A S B 120 Volts FUSE Neg 6G eee The removable Euro Style A C cord that is supplied with the BIG BLOCK 750 makes set ups and tear downs after the gig a snap It also makes de racking much easier when you wish to remove the unit from a POWER FUSE hard wired rack system where all the A C cords have been cabletied in Additional heavy duty cords are available oe sto should you ever need one simply call us direct and we can ship one directly to you for a nominal charge plus 15 shipping cost Make sure the A C cord is firmly in its socket receptacle before powering up the amplifier e NOTE NEVER ALTER THE THREE PRONG POWER CORD IN ANY WAY An eee a TATH This section captures the entire pre amp signal including the Parametric EQ the Compres
3. NOTE BLOCKING THE EXHAUST VENTS WILL CAUSE OVERHEATING AND LEAD TO INTERRUPTED PERFORMANCE OR EVEN DAMAGE TO YOUR AMPLIFIER That wraps up the Overview which has covered the controls and features briefly to familiarize you with the power and possibilities of the BIG BLOCK 750 Now let s get to each of the individual controls and see how they interact to create an individualized sound that is all yours PAGE 2 FRONT PANEL CONTROLS This jack is the instrument INPUT which feeds the first tube the all tube preamp of the BIG BLOCK It is set up with enough headroom to handle both passive and active style instruments For active instruments you may find yourself running the GAIN control somewhere between 10 00 and 2 00 for optimum headroom If you do hear a soft clip creeping in at higher settings don t worry this is the beauty of a tube front end You may feel free to drive the preamp for a more furry character when hyper clean is just too clean SIMUL STATE BASS AMPLIFIER NOTE When driving the preamp with higher settings of the GAIN control it is wise to reduce the BASS control and any low frequencies dialed up on the ACTIVE MID control This will protect accidental damage to speakers and help avoid tubbiness or lack of tightness in the low INPUT TUNER MUTE Se This jack provides a convenient Front Panel output for connection of a TUNER It is wired in parallel with the Rear Panel TUNER
4. EU permission from the Supply Authority is needed before connection READ AND FOLLOW INSTRUCTIONS OF PROPER USAGE BIC BLOCKZS 2 Table of Contents Precautions Overview FRONT PANEL INSTRUMENT INPUT TUNER CONTROLS OVERDRIVE GAIN BASS PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER 0 D MASTER POWER SWITCH REAR PANEL FUSE A C RECEPTACLE GROUND LIFT POST amp PRE DIRECT OUT EFFECTS LOOP Send amp Return FOOTSWITCH TUNER SLAVE SPEAKERS FACTORY SAMPLE SETTINGS PERSONAL SETTINGS PAGE DIAGNOSING PRE AMP TUBE PROBLEMS PARTS SHEET 250 Operating Instructions Congratulations on your choice of the M PULSE BIG BLOCK 750as your amplifier and welcome to the MESA Boogie Family First we would like to thank you for choosing us as your amplifier company This is something we never take for granted and you will come to find that we are here to help you sound your best should you ever need help We feel confident that your new amplifier will bring you many years of rewarding inspiration and create for you a newfound freedom to express through your music This mighty powerhouse joins the innovative band of M PULSE hybrid bass amplifiers as the heavyweight king of headroom with its urgent big venue tone It represents the ultimate marriage of simplicity and versatility and will surprise you daily with its fundamental musicality and tone The BLOCKstands firmly on the same soulful
5. we opted for the tried and true passive style midrange control that has been working great in all of our amplifiers for decades It s hard to improve on a classic In addition to the passive style MID control the BIG BLOCK features an ACTIVE MID circuit that allows further accentuation of specific midrange frequencies across a wide band This wider band covers the spectrum from high bass low mid all the way through to high mid low treble frequencies As you can see this active circuit is made up of two controls a GAIN control which is NGINEE labeled ACTIVE MID that boosts and cuts the selected region and a FREQUENCY control that allows selection of a specific range to manipulate The ACTIVE MID is the gain or amount control It provides 15db of gain in both plus boost and minus cut sass passive Cirections at the specific range selected on the FREQUENCY control Remember that this is a powerful control and that certain frequencies cut through high mid low treble or seem especially loud low mid bass so it is advisable to add gain with the ACTIVE MID control sparingly Set unwisely this circuit is capable of creating sounds that are harsh tubby or just simply unbalanced This combined with the massive power available in the output section can spell real danger to speakers We urge you to use this ACTIVE MID circuit with care and most of all taste to avoid damage to yo
6. D MASTER is only active when the Footswitch is connected to the Rear Panel FOOTSWITCH jack This control gets its feed from the OVERDIVE GAIN and entire Tone Con SDNiSTEK trol Array and allows you to either increase or decrease the playing volume relative to the Clean O AC OFF normal mode OVERDRIVE B This is especially important because overdriven sounds are more compressed than clean sounds and as greater amounts of overdrive are added it will compress the signal more making the relative volume to the normal mode seem lower NOTE The OVERDRIVE LED will illuminate when the OVERDRIVE mode is activated with the Footswitch indicating that both the OVERDRIVE and O D MASTER in the signal path and active KOANLA This switch delivers the A C power to the BIG BLOCK 750 Make sure the unit is grounded all three terminals of the A C power cord must be connected whenever possible to avoid injury to the user as well as to the amplifier Also make sure that the proper voltage requirements are present at the A C wall socket receptacle NOTE As a reminder never alter the A C power cord in anyway for possible damage to the amplifier may occur not to mention the possibility of a fire outbreak BIGBLOCK75 J O D MASTER Now that we have reviewed the features and controls on the Front Panel let s take a spin around back and review the interfacing connections REST AREA
7. far beyond that of a conventional passive type control It can increase the low end to an almost absurd level and with a flick of the wrist dip it to near transitor radio skinniness Needless to say with any control this powerful a certain amount of finesse must be applied to achieve musical results Be especially mindful of this when using the 5 Band Parametric in conjunction with the BASS control This is the only passive style control in the string of rotary tone controls This scheme was chosen for its inherently musical blend and for the way the passive style midrange control with its wide spread and smooth taper fills in the holes Unlike the BASS this control is a boost only and while it can competently remove this broad spectrum of midrange from the Mrs 1111 mix it cannot provide the extreme attenuation of an active style control You will find as we did that this control works amazingly well for WV overvaive PASSEND shaping the midrange frequencies with a natural earthiness and INPUT TUNER character that is a perfect counterpart to its neighbors It is hard to dial wrong with this more forgiving control as it seems to give you just enough and no more For radical and specific scooping of the midrange frequencies for modern R amp B and Funk styles there is plenty of notching power that is infinitely more accurate to be found in the ACTIVE MID Because of this
8. pt 593151 POT pt 593148 POT pt 593148 JACK pt 619112 POT pt 592379 LENSpt 703782 POT pt 593737 BLUBpt 703047 JACK pt 619112 KNOB pt 408004 POT pt 592379 JACK pt 619112 JACK pt 619112 JACK pt 619102 REAR VIEW Big Block 750 CAUTION Unplug pow power before removin bolts holding chassis POWER FUSE 120 V 15 60Hz 510 15 BLO p 613713 BIG B BASS EN MOSFI SUGGESTED LOAD 2 OHMS MINIMUM DIRECT OUTPUT LEVEL ALIFORNIA JACK KNOB pt 408004 620555 POT pt 593151 JACK pt 620550 SWITCHES pt 607111 JACK pt 619102 PAGE 14 The Spirit of Art in Technology Thank you for trusting MESA Boogie to be your amplifier company and we wish you many years of toneful enjoyment from this handbuilt all tube instrument The Spirit of Art in Technology 707 778 6565 FAX NO 707 765 1503 1317 Ross Street Petaluma CA 94954 USA
9. sounding ground as M PULSE amplifiers with architecture based on our 30 years of all tube preamp experience and Szmul State Power which utilizes a tube driver stage feeding a bank of custom designed mosfet output devices This design seamlessly integrates the best sonic qualities of old world tube circuitry and modern high power mosfet technology to arrive at a stunning blend that is both musical and powerful In the BIG 750 case that is doubly true This monolith of tone harnesses not one but two power blocks putting at your immediate disposal ridiculous amounts of transient handling current produced by the 20 mosfet devices This means when you want to say something with your instrument your voice will be heard with accuracy both harmonically and in the time domain Every bassist knows how important that is FRONT VIEW Big Block 750 Gass OVERDRIVE BASS PASSIVE MID FREQUENCY TREBLE MASTER 0 D MASTER INPUT O 2 5 STAGE VACUUM TUBE AMPLIFIER REAR VIEW Big Block 750 M PULSE BIG BLOCK 750 n EVEL hots honing elmer SIMUL STATE BASS AMPLIFIER TUBE DRIVEN MOSFET POWER A POWER FUSE 120V 15 15 BLO Rew FOOT ee 6 Y T HANDBUILT IN PETALUMA CALIFORNIA PAGE 1 Overview Continued Looking the Front Panel it is apparent how logically the controls are laid out befor
10. stepping out can be easy and controllable You won t have to rely band dynamics or house sound engineers to give you a little volume bump when you need it MUTE Setting the OVERDIVE control above 12 00 reveals the higher gain potential of this circuit Here a wide range of more obviously overdriven sounds appear that can be used to mimic an analog synth or provide the grinding aggression for a integral part in a heavy song This range showcases how amazingly tight the overdrive tracks and makes this mode an essential part of the BIG BLOCK S sonic power and magic PAGE 3 FRONT PANEL CONTROLS Continuea Note that the GAIN control is still active when the OVERDRIVE is switched into the signal path The GAIN control is wired in series with the OVERDRIVE and therefore it can be used to further fine tune the amount of overdrive present in the mix The effect of the GAIN control is more apparent at the lower region of the OVERDRIVE control where sweeping the GAIN is very noticeable At higher OVERDRIVE settings it has a fairly diminished effect Generally speaking the sound will brighter and more scooped in the mids at lower GAIN settings while higher settings will produce a fuller richer sound with less emphasis on upper harmonics We hope you find the OVERDRIVE mode a fun and musically expanding addition to an already amazing sounding preamp Over time we believe you wil come to findit an invaluable part of your sound GAIN Thi
11. take many forms but can generally be described in two catego ries Noise and Microphonics Noise can be in the form of crackling sputtering white noise hiss and or hum Microphonic problems usually appear in the form of a ringing or high pitched squealing that gets worse as the gain or volume is increased thus are more noticeable in the higher gain HI modes Microphonic problems are easily identified because the problem is still present even with the instruments volume off or unplugged altogether unlike pick up feedback which ceases as the instrument is turned down Micro phonic noise is caused by mechanical vibration and shock think of banging a microphone around and you ll understand where the word came from The best way to approach a pre amp tube problem is to see if it occurs only in one specific mode or channel This should lead you to the tube needing replacement If you cannot narrow down the trouble to a specific mode or channel the problem may be the small tube that drives the power tubes which is operational in all modes and channels Though rare a problem with the driver tube would show up in all aspects of performance so if you can t narrow the problem down to being mode or channel specific you want to try replacing the driver tube Driver problems generally show themselves in the form of crackling or hum in all modes of performance and or weak overall output from the amplifier lt 9 NOTE When remo
12. MEsA BOOGIE BIG BLOCK75 Owner s Manual Greetings from the Home of Tone Congratulations on your choice of the Big Block 750 as your Bass amplifier and welcome to the MESA Boogie family As a discriminating player you probably know that you have purchased the most comprehensive instrument for amplifying Bass that is available What you might not realize is that this entitles you to all the experience resources and commitment our twenty five years of service to musicians world wide has to offer Our responsibility is to help you sound great So if at any time you feel you need help or direction we are here for you a phone call away PRECAUTIONS amp WARNINGS Your MESA Boogie Amplifier is a professional instrument Please treat it with respect and operate it properly USE COMMON SENSE AND ALWAYS OBSERVE THESE PRECAUTIONS WARNING Vacuum tube amplifiers generate heat To insure proper ventilation always make certain there is at least four inches 100mm of space behind the rear of the amplifier cabinet Keep away from curtains or any flammable objects WARNING Do not block any ventilation openings on the rear or top of the amplifier Do not impede ventilation by placing objects on top of the amplifier which extend past the rear edge of its cabinet WARNING Do not expose the amplifier to rain moisture dripping or splashing water Do not place objects filled with liquids on or nearby the amplifier WARNING Always make cer
13. RECT LEVEL control allows you to match levels to all types of consoles There is also a GROUND LIFT switch for the DIRECT circuit to help ensure a quiet signal when connecting to consoles that may have different ground references A dedicated TUNER circuit with both Front and Rear Panel Outputs features footswitchable MUTE function for silent tuning when the footswitch is connected in stage or studio environments Outboard processing is handled through the series EFFECTS LOOP which is activated when cables are inserted into the SEND and RETURN jacks A SLAVE OUTPUT and dedicated LEVEL control are provided for capturing the entire sound of the preamp and power section This is useful when another BIG BLOCK or additional power amplifiers are needed for large coliseum size venues In this scenario the SLAVE is the perfect feed signal because it will pass on everything you do to the sound and give you control over the signal strength The BIG BLOCK delivers its massive power to the ground via the SPEAKER OUTPUT section which offers two types of jacks for cabinet interfacing Standard jacks allow connection under any scenario with any cable while the heavy duty NEUTRIK SPEAK ON connectors lock the cable in place for speaker enclosures that incorporate this system as a design feature Finally two punched grille vents serve as exhaust ports for the heat that is forced out of the two mosfet power blocks by the dual cooling fans NEVER BLOCK THESE VENTS
14. VE BASS PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER 0 D MASTER be 75 600000965 5 STAGE VACUUM TUBE AMPLIFIER PAGE 11 PERSONAL SETTINGS SHEET 10 care WZ OVERDRIVE BASS 0 0 8 PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER INPUT ae 10108010 5 STAGE VACUUM TUBE AMPLIFIER CEE 2222722 overvrive BASS O D MASTER Gs PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER INPUT pa 5 STAGE VACUUM TUBE AMPLIFIER cera SIMULSTATE BASS AMPLIFIER ENGINEERING SZ overprive BASS PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER INPUT pi AIT 8166 OVERDRIVE 5 STAGE VACUUM TUBE AMPLIFIER CSCS C e WZ OVERDRIVE BASS 0 0 PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER INPUT a Om OVERDRIVE 5 STAGE VACUUM TUBE AMPLIFIER PAGE 12 Some point it is quite possible that you will experience some kind of minor pre amp tube noise Rest assured this is no cause for alarm and you can take care of the problem yourself in a matter of minutes by simply swapping tubes It is always a good idea to keep at least a couple of spare pre amp tubes on hand at all times to insure uninterrupted performance These minor pre amp tube problems can
15. ack system The Footcontroller MUTE switch activates the MUTE feature in both Front and Rear outputs simultaneously The SLAVE feature provides a padded signal that is derived from the Speaker Output and captures the entire sound of the preamp and power section This is useful for large venue applications where multiple BIG BLOCK or other slave amplifiers are strung together for additional power to drive more speaker enclosures LeveL SLAVE OUT O The SLAVE may also be used as a send signal to feed outboard processing racks in a dry wet setup where processing is done after the BIG BLOCK 750and then fed to a Stereo power amplifier for separate control of the wet sound This works very well and is similar to what is done in the recording environment where a dry signal is blended with another channel on the console that is only the processed wet version of the same sound NOTE Once a signal has been taken from the SLAVE you can not feed the signal back into the BIG BLOCK Effects RETURN jack or INPUT Doing so will cause a feedback loop resulting in a high pitched squeal much like a microphone held up to a monitor You must go into an external amplifier or device once a signal has been taken from the SLAVE NOTE Always start with the SLAVE LEVEL at 7 00 off and increase the level slowly to prevent damage to ears speakers and the input stage of external processors NOTE The SLAVE is not optimized for direct interfacing into recordin
16. arge venue house application GROUND LIFT This switch removes the circuit to chassis ground connection from the XLR jack Leave it in the grounded position switch down normally unless you experience a hum when connecting to a console If you do experience a hum when connecting the XLR Output to a console try lifting the ground switch up on the circuit This will usually but not always remedy most ground loop type noise from the signal path Sometimes it may also be necessary to lift the A C Cable Ground also by using a 3 2 ground adapter to achieve a quiet signal path NOTE Ground loops can occur in many places in a complex signal path The DIRECT OUTPUT GROUND LIFT switch is not a cure all and therefore should not be expected to remedy every type of ground related problem These two jacks provide an interface for external signal processors and they access a point between the preamp and power section This wiring scheme creates a Series Effects Loop that is well matched to the input and output impedance of most good quality processing devices The jacks used in the loop are switching type jacks meaning that when W PULSE BIG BLOCK 750 nothing is inserted into either SEND or RETURN the preamp signal bypasses the jacks When cables are SIMUL STATE BASS AMPLIFIER inserted the signal path is interrupted and sent through the EFFECTS LOOP TUBE DRIVEN MOSFET POWER _EFFECTS _ Because the loop is wired in series anything you do to the signal her
17. bined with the GAIN create the best tone they have ever heard NOTE As with the BASS control may we remind you that a control of this type with its increased power should be used with finesse In the TREBLE S case almost more so because higher frequencies seem louder to the ear and are generally more painful when set to extremes Another reason to use care is that high frequencies tend to increase the ambient noise floor when set too high This is then exacerbated if the 5 Band Parametric is combined for added top end boost Dial with care and music in mind The MASTER control is the feed to the Simul State power section and determines the overall playing volume of the BIG BLOCK 750 An optimum setting will be determined by the setting of the GAIN control as well as the entire tone control network All these controls affect the signal strength at the end of the preamp and can make the MASTER control very sensitive NOTE Remember to use with caution as the MASTER is the gas pedal for the massive power available We suggest a zero setting at each power up to avoid damage to speakers and ears TREBLE MASTER OO PAGE 6 FRONT PANEL CONTROLS Continued OF A This control like the OVERDRIVE is designed to help you think outside the box It provides an independent volume control for the OVERDIVE mode allowing you to preset the level of the overdriven sound and footswitch to it for specific parts The O
18. e will affect the entire sound of the amplifier Therefore we suggest using only the highest possible quality of processing devices and the 4 best possible low capacitance cables of the shortest possible length RETURN SEND NOTE Cable lengths of 1 foot are best with 3 feet being about the longest desirable length Using longer interface cables in the series loop will introduce unwanted capacitance and begin to roll off top end and attack To use the EFFECTS LOOP 1 Connect the SEND jack to your processors INPUT 2 Connect the RETURN jack to your processors OUTPUT 3 Adjust the dry wet blend with your processors MIX WET OUTPUT control 29 51 This 1 4 stereo jack accepts the stereo phone plug from the included BIG BLOCK Footswitch Connecting the FOOTSWITCH via this jack allows remote activation of the OVERDRIVE and SOLO features TUBE DRIVEN MOSFET POWER These two features can only be activated when the FOOTSWITCH is connected ET EFFECTS The Front Panel controls for these features are bypassed when the FOOTSWITCH lam la is disconnected RETURN SEND DIRECT OUTPUT LEVEL HANDBUILT IN PETALUMA CALIFORNIA PAGE 9 REAR PANEL CONTROLS Continued Sy This Rear Panel auxiliary TUNER output is wired in parallel with the Front Panel TUNER output This provides for Rear Panel interfacing of rack mount tuners where it is preferable to have all wiring stay in the rear of a r
19. e you creating a simple and intuitive platform for expression However don t let this simplicity deceive you as to the incredible shaping power of this preamp The tone controls are voiced such that minimal shaping is needed to achieve a warm musical blend yet should you want to create your own signature sound they can take you anywhere you wish to go quickly and effortlessly This tone control stack features two MID controls A wide band passive MID works magically with the wide band active BASS and TREBLE controls to create a balanced spatial blend while a semi parametric MID allows frequency specific shaping over a wide range that covers low mid and high mid low treble frequencies This array is simple to use yet provides all the shaping power you will need while keeping the tweaking to an inspiring minimum In addition to this traditional gain stage the BIG BLOCK features an all tube overdrive stage with its own separate OVERDRIVE and MASTER controls This footswitchable mode brings everything we ve learned building high gain guitar amplifiers over three decades to focus on bass guitar and creates an incredible new frontier of truly usable overdriven bass sounds The Rear Panel neatly showcases all the features you would come to expect in a amplifier of this caliber and ensures all your interfacing needs are covered A balanced XLR DIRECT OUTPUT captures the entire preamp signal and features both PRE and POST options while its dedicated DI
20. es things in the time domain BASS This control is responsible for the basic mix of low frequencies in the tube pre amp The BASS control is an active shelving type control as opposed to a passive style control This means that a center Q point has been chosen and this control allows you to either boost or cut that frequency This control differs from the low bands of the Parametric in that it has a broader Q point with a more gentle ramp as QUD 1111 opposed to the Parametrics narrow Q that is used with a separate GAIN control The BASS control is actually a gain and frequency control all rolled into V Y overvrive GAIN BASS one with the Q center at 55Hz and harmonics in both low and high direc INPUT TUNER tions are affected because of its broader band nature As the control is C increased past 12 00 there is 690 per octave rise in gain with the fre MUTE quency topping out at 321Hz With 12 00 straight up representing flat a no boost no cut setting As the BASS control is dialed below 12 00 55Hz and all associated harmonics are reduced and eventually notched com pletely out of the signal Conversely there is a per octave cut beginning at 55Hz going down to 20Hz where the shelving ends with a cut gain of 20db as the control approaches 7 30 off PAGE 4 FRONT PANEL CONTROLS Continued This type of broad band active rotary control makes it possible to achieve bass characteristics
21. g consoles or live mixing boards For this application it is best to use the DIRECT OUT SPEAKERS These two sets of outputs are responsible for delivering the mighty power of the BIG BLOCK to your speaker enclosure s of choice We would like to suggest that if you have not already auditioned one of our many incredible new Bass Enclosures that you do so at your earliest convenience They have been designed to deliver the ultimate tone and maximum power from your amplifier and we feel confidant that like us upon hearing them you will find the competition disappointing Two styles of speaker connectors have been provided so that any type of cabinet configuration may be interfaced with the BIG BLOCK NEUTRIK brand SPEAK ON Connectors provide for locking 1 4 interfacing and all MESA Bass Enclosures will come standard with these additional heavy duty jacks SUGGESTED LOAD 5 In addition the standard 1 4 phone jacks are also supplied for older cabinetry that does not support these SPEAK ON connectors Your BIG BLOCK was designed so that it will deliver its maximum power 750 watts RMS at an impedance load of 2 Ohms and it can do so without worry of overheating However feel free to use any combination of cabinets with a combined load above that impedance with no worry of damage to the amplifier At higher impedance loads 4 or 8 Ohms overall power will be diminished but this works out in your cabinets favor as so
22. htly wadded up newspaper so there is at least six inches of crush space between the chassis and the cardboard box Bubble wrap also works well but please DON T use styrene peanuts they will shift during transit and get lodged inside your electronics as well as allowing your amp to end up at the bottom of the box unprotected and possibly damaged Pre amp tubes don t normally wear out as a rule Therefore it is not a good idea to change them just for the sake of changing them If there isn t a problem don t fix it If there is no result from your substitutions it may be possible that you have more than one problematic tube Though rare this does happen and though it makes the troubleshooting process a little more intimidating it is still possible to cure the problem yourself NOTE It is normal to hear a slight metallic ringing sound when tapping on the preamp tubes As long as the tube does not break into oscillation or start crackling or any other form of bizzare noise it is considered normal and functional PAGE 13 SWITCH ALL FRONT PANEL KNOBS SAME FRONT VIEW Big Block 750 408114 pt 600631 OVERDRIVE GAIN BASS PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER 0 0 ic O O O D A 2 OVERDRIVE POT pt 593151 POT pt 593151 POT pt 593151 POT 592155
23. me cabinets may not be rated to take the full assault of the awesome power available in the BIG BLOCK output section NOTE It is possible to use the DIRECT OUT for recording direct to consoles with no load present no Speaker cabinet connected on the SPEAKER OUTPUT without worry of damaging the amplifier That covers the features of the BIG BLOCK Rear Panel and now with the combined understanding of the controls you should be able to dial with confidence as you search for your signature sound We wish you many years of inspiration and musical fulfillment from your new amplifier From the entire MESA Family CHEERS PAGE 10 FACTORY SAMPLE SETTINGS SAMPLE SET 1 Round Warm R amp B Csa be NZ OVERDRIVE BASS PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER 0 0 INPUT O O AC i ure O O O 5 STAGE VACUUM TUBE AMPLIFIER SAMPLE SET 2 Scoopy Sla be OVERDRIVE BASS ACTIVE MID FREQUENCY TREBLE O D MASTER INPUT TER O O O senate 5 STAGE VACUUM TUBE AMPLIFIER SAMPLE SET 3 Purring Edge be 2 2 OVERDRIVE BASS PASSIVE MID ACTIVE MID FREQUENCY TREBLE MASTER 0 D MASTER O QO O O W 4 OVERDRIVE 5 STAGE VACUUM TUBE AMPLIFIER SAMPLE SET 4 Overdrive Solo ENGINEERING INEERING OVERDRI
24. output There is an optimum padded signal present at all times on both Front and Rear jacks There is a MUTE function and LED indication which is only controllable from the Footswitch There is no mute function avail 5 COULD able when the Footswitch is disconnected la lan OVERDRIVE OUTPUT INPUT TUNER VEL o XO gt MUTE TUBE DRIVEN MOSFET POWER EFFECTS SWITCH TUNER A CALIFORNIA This control determines the amount of all tube OVERDRIVE that can be blended with the regular clean preamp signal This circuit creates a whole new realm of sounds that range from a soft clip purr to fully saturated grind The OVERDRIVE has been tailored specifically for bass applications and does not disturb the blend dialed up on the tone controls The OVERDRIVE circuit is activated via the included Footswitch and the combination of the e Front Panel OVERDRIVE control which determines the amount and the O D MASTER which gives you control over the volume of the OVERDRIVE means that this feature creates a channel switching option that can be used for a wide range of choices OVERDRIVE In the lower region of the OVERDRIVE control you will find that a subtle boost can create INPUT TUNER footswitchable soloing options where the added gain is merely thickening rather than saturat SIMUL STATE BASS AMPLIFIER ing the signal Because this circuit has its own MASTER control
25. s control determines the overall character of the input sensitivity The lower regions of the control below 12 00 lend greater headroom and provide a scooped brighter personality The upper harmonics come through more prominently in this area of the control making the top end sound more transparent and sweet This region is especially useful for funkier stuff when thumbing is in order It keeps the rubber band feel intact in the lows and mids while voicing the snap just high enough to avoid harshness or the dreaded gak when the G string is plucked QIED As the GAIN control is increased past 12 00 a richer more well rounded voice AE becomes dominant and headroom starts to diminish in increments until eventu ally a tube overdrive sound appears as the 12AX7 input tube is driven into satura OVERDRIVE GAIN INPUT TUNER The region between 12 00 and 2 30 is where the classic warm tube sound re sides and within this narrow band you will discover world of tone Tiny incre ments here produce subtle but important differences in the attack characteristic which in turn feel like changes in the time domain MUTE By experimenting with the amount of gain you can actually voice the amp to feel as if it bounces just ahead of the groove or lays back a little deeper to produce a more Fatback feel The difference in attack and sustain produces striking results as to how the bassist and in fact the whole band perceiv
26. sor and the Effects Loop and allows you to send a Balanced signal to either a House Main Board or a Recording console There are four elements to this circuit which are 1 a male XLR jack 2 a LEVEL control 3 a POST PRE switch and 4 a GROUND LIFT switch Here are their functions and how to use them CAUTION Unplug power i post PRE LEVEL This rotary control allows you to set an appropriate level for the Direct 45 Signal to match the input sensitivity of the console It is always best to start with the LEVEL control zeroed out before connecting a cable to the DIRECT output POWER FUSE This practice will help to avoid accidental damage to the speakers or your pars 8 enginneers ears from too hot a setting upon hitting your first note 15 1810 DIRECT OUTPUT LEVEL POST PRE This switch lets you choose the type of signal you wish to send to the console POST gives you the entire sound of the pre amp with the Parametric EQ HANDBUILT IN PETALUMA CALIFORNIA Compressor and the Effects Loop including processing from anything in the loop PAGE 8 REAR PANEL CONTROLS en We Od 3 PRE gives you just the sound of your instrument and no BIG BLOCK 750 enhancement so that an engineer can create their own sound with your unprocessed signal at the console This is very handy for sound reinforcement applications as the sound you use on stage may be too big with enhanced low end for a l
27. tain proper load is connected before operating the amplifier Failure to do so could pose a shock hazard and may result in damage to the amplifier Do not expose amplifier to direct sunlight or extremely high temperatures Always insure that amplifier is properly grounded Always unplug AC power cord before changing fuse or any tubes When replacing fuse use only same type and rating Avoid direct contact with heated tubes Keep amplifier away from children Be sure to connect to an AC power supply that meets the power supply specifications listed on the rear of the unit Remove the power plug from the AC mains socket if the unit is to be stored for an extended period of time If there is any danger of lightning occurring nearby remove the power plug from the wall socket in advance To avoid damaging your speakers and other playback equipment turn off the power of all related equipment before making the connections Do not use excessive force in handling control buttons switches and controls Do not use solvents such as benzene or paint thinner to clean the unit Wipe off the exterior with soft cloth YOUR AMPLIFIER IS LOUD EXPOSURE TO HIGH SOUND VOLUMES MAY CAUSE PERMANENT HEARING DAMAGE No user serviceable parts inside Refer service to qualified personnel Always unplug AC power before removing chassis EXPORT MODELS Always insure that unit is wired for proper voltage Make certain grounding conforms with local standards WARNING
28. ur ears and speakers These two simple controls offer an incredible amount of shaping power in a simple to use format When combined with the other tone controls virtually any sound you desire is available to you quickly and with far less searching than when using multi band equalizers This simplicity is at the heart of the BIG BLOCKS character great tone with minimal tweaking PAGE 5 FRONT PANEL CONTROLS Continuea This control determines the frequency range that the ACTIVE MID control will cut or boost As mentioned earlier it covers a broad range that sweeps from the low midrange region to the lower treble frequencies The control sweeps from 200Hz on the low side to 2Khz on the high side with 340 Hz riding the center straight up at 12 00 on the control This sweepable band gives you pinpoint shaping power over the broad and usable midrange spectrum and also allows some overlap the extreme ends of the control with the adjacent broad band BASS and TREBLE controls ee May we again remind you to use care and taste when dialing with this powerful control Some fre PASSIVE MID ACTIVE MID FREQUENCY quencies stick out or cut more than others making it possible to add unwanted unpleasant and even O O dangerous peaks or blow unbalanced holes in your sound We suggest dialing in your sound with the standard tone control array first and then using the ACTIVE MID circuit to fine tune and subtly enhance your sound
29. ving a tube from its socket grasp tube near the q gt and rockgently from side to side while simultaneouslypulling upward TD Pa 9 7 S 2 Sometimes making the diagnosis is more trouble than it s worth and it s faster and easier to merely replace the small pre amp tubes ONE AT A TIME with a replacement known to be good But MAKE SURE you keep returning the tubes to their original socket until you hit the one that cures the problem You ll notice that tubes located nearer to the INPUT jack always sound noisier but this is because they are at the start of the chain and their noise gets amplified over and over by the tubes that follow The tube that goes into this input socket usually labeled V1 needs to be the least noisy of the bunch The tube that goes at the end of the preamp chain just ahead of the power tubes can be quite noisy without causing any problem at all The tubes in your amp have already been located in the most appropriate sockets and this is why you should NEVER pull them all out at once and ALWAYS swap them one at a time ALWAYS return a perfectly good tube to its original socket Also it s a good idea to put the amp on STANDBY when swapping tubes to reduce the heat build up in the tubes themselves and to prevent explosive noises which can still occur even if you are pulling the tubes away from their sockets gently from coming through the speaker To wrap the chassis use plenty of tig
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