Mesa/Boogie Rectifier Stereo Stereo Amplifier User Manual
Contents
1. RECTIFIER STEREO 2 ONE HUNDRED Owner s Manual Hello from the Tone Farm YOU the smart player and all around intuitive human have put your trust in us to be your amplifier company This is something we do not take lightly Our reward is that we ve made a classic amplifier and by choosing this amplifier you have become part of the MESA family Welcome Our goal is to never let you down Your reward is that you are now the owner of our most popular selling power amp the 2 100 Bred of fine all tube amp heritage benefiting from the many patented pioneering MESA Boogie circuits that led to the refinement of your new instrument Feel confident as we do this product will inspire many hours of musical satisfaction and lasting enjoyment It was built with you in mind by players who know the value of a fine musical instrument and the commitment it takes to make great music The same commitment to quality value and support we make to you our new friend RECTIFIER STEREO 2 ONE HUNDRED TABLE OF CONTENTS Precautions OVERVIEW FRONT PANEL CONTROLS amp SWITCHES LEVEL CONTROLS PRESENCE POWER ON STANDBY MODERN REAR PANEL SWITCHES amp JACKS INPUTS A B BIAS SWITCH GROUND LIFT SPEAKER JACKS TUBE BAY DRIVER TUBES 12AX7A AC RECEPTACLE LINE FUSE TUBE MAINTENANCE DIAGNOSING POWER TUBE FAILURE DIAGNOSING PRE AMP TUBE FAILURES amp PROBLEMS Feature Article by Randall Smith On Bias2. otherwise you would die from electrocution Contrast this with your car battery which puts out a mere 12 volts You can lay your hands right across the terminals and not feel a thing Yet the amount of current available can run to several hundred amperes enough to turn over a cold engine and get it started So current and voltage are two totally separate electrical parameters though when you multiply them together you get POWER which is measured in watts When you set the bias of an amplifier you are adjusting the static VOLTAGE at the control grid of the tube in order to produce a desired amount of idle CURRENT flowing to the tube s plate A small change in grid voltage produces a large change in the amount of current flowing and that s basically how a tube works Say that again because it s super important A small change in voltage at the grid causes a large change in current flowing to the plate See that s the essence of amplification A small change causing a large change And here it s a small voltage change causing a large current change The bias conditions are what determines how much current flows through the big power tubes when you re not playing And what drives your speakers is flucuations in that current flow when are ARE playing If the amount of current increases and decreases 440 times per second then you ll hear an A note If the fluctions in current flow are large and still at 440 per second you ll hear an A that
3. Ginter n 4 Grounds being connected via the ground lugs of the power cords on the units The rule of thumb here LIFT NORMAL P gt x E A 85 that one and only one unit in a rack should have a connection to the AC power ground all the other SLO units in the rack should have their grounds lifted by using 3 to 2 adaptors on their AC plugs We suggest grounding the Power amp no adapter 2 Ground loops occuring because of two or more audio cables connecting two components The most common solution is to diconnect the shield from the sleeve connection at one end of some of the inter connecting cables so that only one cable between each device has an intact ground shield Some experimentation is required to find which cable is best for conducting the ground and which cables are best suited to have the special clipped ground We recommend trying the intact ground cables for the signal path which flows say from an Effects Send jack to an effects unit and trying the clipped ground method on the cable which connects the effects output back into an Effect Return 3 Ground loops created by the physical contact between the metal chassis of the components and the steel rack rails It is for this third type of ground loop that the GROUND ISOLATION Switch was provided This switch effectively lifts the electronic circuit ground from the metal chassis ground which otherwise must be done manually by disconnecting a wire inside of the amp Here a
4. They are as follows EE When you wire hook up speakers in Series the speakers resistance as measured in ohms is additive i e putting two 8 Ohm speakers in Series results in a 16 Ohm load POSITIVE mon Speaker 8 Ohms Speaker B 8 Ohms SERIES Connect the Negative side of Speaker A to the Positive side of Speaker B PAGE13 SPEAKER IMPEDANCE MATCHING amp HOOK UP GUIDE continued When wiring in parallel the resistance of the speakers decreases Two 8 Ohm speakers wired in hooked up Parallel results in a 4 Ohm load It s easy to calculate the effect of a resistive load when all the speakers are all the same resistance It is really not suggested to wire different resistive load values in Parallel 8 and 4 16 and 8 etc The formula for figuring the total impedance in Parallel is the multiplication of the two loads divided by the sum of the two loads i e putting two 8 Ohm speakers in Parallel results in a 4 O hm load Connect the Positive side of Speaker Ato the Positive side of Speaker B Connect the Negative side of Speaker A to the Negative side of Speaker B Speaker A 8 Ohms Speaker B 8 Ohms CD a 8 ea WC NEGATIVE POSITIVE Total Load 4 Ohms te ETUC Rej RS RH This is really just two sets of Parallel wired speakers connected in series This is how you maintain a consistent load with multiple speakers All 4 Spkrs are 8 Ohms than one
5. you can spot the tube at fault and replace it alone at e considerable savings over replacing all the output tubes A tube that arcs or flashes over inside should be replaced immediately In an emergency you can just remove the 1 bad tube and go on with the show running on 3 cylin ders Sometimes a tube will short out intermittently turn ing red hot all over the large metal plate inside But usually a momentary switching off of the STANDBY or POWER Switch will enable the tube to straighten out its electron flow and return to proper operation Should this happen repeatedly careful observation will usually reveal which tube is shorting even though one or two others may also turn red hot after a few moments M MESA Boogie type STR 430 8 x 6L6 By viewing the tubes try to verify which one is reddest or turns red first that is the bad one and the others are most likely unharmed Internal circuitry is built to withstand tube failure as much as possible even if damage were to occur it would be minor and easily repairable When replacing tubes please use only the MESA Boogie types specified Using other tube brands and or types will invalidate your amplifier s warranty To remove tubes you must first push back the spring retainers clamped against the tube base When re installing power tubes check that the spring clamps are making good contact with the tube base bend them in toward the center before plugging in the tube if nece
6. Adjustment SPEAKER HOOK UP GUIDE amp IMPEDANCE MATCHING POSSIBLE HOOK UP SCHEMES Amplifier to Speaker Cabinets WIRING EXAMPLES USING THE SIMUL CLASS 2 100 Feature Article By Randall Smith On How Tubes Work 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 EU permission from the Supply Authority is needed before connection 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 certain 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 us
7. PRESENCE POWER STANDBY PRESENCE PAGE 2 FRONT PANEL CONTROLS ee E due ug First remove the protective covers from the tubes plastic webbing before con ji eee the A C cord to a power receptacle Make all necessary connections including pre amp effects speakers and instrument before gt a Cae you flip the STANDBY switch to its ON position AC power is turned on via the POWER switch VELA wv indicated by the pilot lamp Before switching on the power place the STANDBY switch into BERE its Standby position and allow at least 30 seconds of warm up time before switching the STANDBY P o amp G switch to the ON position ENCE POWER stanpey PRE This start up procedure helps extend tube life by preventing a high voltage turn on surge How ever all of our amplifiers are tested to withstand this extra stress just in case this procedure is neglected by the user But ignoring this procedure everytime the amplifier is used will shorten the tubes toneful life Never remove any of the power cords terminals All three terminals of the A C power cord must be connected and always check that the power receptacle has the proper voltage present Also make sure that the power cord is inserted all the way in when connecting to a power receptacle SURESH Perfect for set breaks this toggle switch also serves an even more important purpose In the standby position the tubes are at idle so that during power up the
8. bar and you can easily picture an orderly if rapid movement of the lot in a single direction This is what happens when a positively charged element called the anode or plate is introduced into the vacuum The plate is the large metal element most prominently visible through the glass of an electron tube It is the outermost element of a tube s structure and it surrounds all the others The cathode is at the center radiating electrons outwards As higher and higher positive voltage is applied to the plate the attraction for the electrons surrounding the cathode is increased and with nothing standing in the way full uninhibited flow to the plate occurs sort of like removing the doors and offering free drinks to the crowd of surly Irishmen milling around outside As electrons flow to the plate the space charge will continually be replenished by further boiling of the hot electron rich cathode as you can easily imagine other Irishmen impatiently taking up the places of those who ve gone inside until the entire village is deserted Now where do they come from and how do they emerge Well a grand and elegant lady once showed me how to revive flat champagne She dropped a raisin into the glass There was a dramatic and immediate increase in effervescence with the introduction of a cathoding surface Thousands of tiny bubbles suddenly appeared and continued to flow from the raisin Of course the bubbles were made up of gas dissolved in the beve
9. batch shown on its label Call us and we will send one out to you The severe short is not nearly so benign In the worst cases a major arcing short occurs between the plate and the cathode with visible lightning inside the glass and a major noise through the speaker If this is seen to happen IMMEDIATELY turn the amp to STANDBY By this time the fuse probably will have blown Such a short is usually caused by a physical breakdown inside the tube including contaminate coming loose or physical contact or near contact between the elements Replace it and the fuse with the proper slo blo type and power up the amp using the power up procedure as we described earlier in this manual Often caused by contamination within in a tube the culprit can usually be identified and by lightly tapping on the glass you will probably hear the noise change Hearing some noise through the speakers while tapping on the 12AX7 s is normal however And the one nearer the INPUT will always sound louder because its output is being further amplified by the second 12AX7 The power tubes should be all but quiet when they are tapped If crackling or hissing changes with the tapping you have probablyTUBE NOISE CONTINUED found the problem To confirm a noisy power tube merely put the 2 700 on Standby remove it from its socket and turn it back on It will cause no damage to run the 2 700 briefly with one power tube missing You may notice a slight background hum
10. exactly true to the signal path between preamp and power section as it occurs in the Dualand Triple Rectifier Heads To achieve this duplication a driver tube responsible for the effects return stage and all related circuitry in the 2 700 must be removed and this includes the LEVEL Conbtrols as they are part of this circuitry As a result when using the RECTO INPUTS you will use the Recto Pre LIVE OUTPUT Control as your overall final master level control Your 2 100 was designed with versatility in mind The BIAS SWITCH allows you to adapt the power output section of the 2 200in order to use the other classic pentode power tubes the British style EL 34 These tubes are largely responsible for the signature sound of many immediately identifiable and wonderful sounding amps created in Great Britain and used on some of the best recordings to date The nature of their sound is usually brighter in the extremely high frequencies some players find this almost thin at first However aficionados of the EL34 BIAS P normat le bowen Sound know that nothing has the lushness of harmonics or spread like a power amp using EL34 s In i Ug truth EL34 s do focus in on a region of upper harmonics that 6L6 s reproduce but not really enhance in SN HM the same way the EL34 s do RECTO INPUT MUST MATCH TUBES f This characteristic is sometimes preferred for sounds that range from a soft clip that would be used for chording or soloing to an al
11. is LOUD But for purposes of biasing it s the amount of plate current flowing with no signal applied that s important Unfortunately current is hard to measure because the circuit must be interuppted as in cut the wire and the meter spliced in series with the broken circuit But measuring VOLTAGE is easy It is not necessary to interrupt the circuit because a voltage reading can be taken in PARALLEL with the circuit intact Thus as a matter of convenience most bias settings are given in volts at the grid even though current through the plate is the important factor In fact plate current is so inconvenient and dangerous to measure that Fender doesn t even state what the correct value should be They only give the grid voltage that will produce that current That s the minus 52 But that only happens if the tubes being used are in spec As long as the tubes ARE in spec the right bias voltage will always give the correct plate CURRENT but then there s no need for the bias voltage to be adjustable If the tubes are NOT in spec then the only proper way to re set the bias is to cut the circuit and measure the current while adjusting the bias but no manufacturer know even STATES the desired current value Be that as it may when the original bias voltage is altered far enough it will compensate for the tube s abnormal performance and the correct amount of idle current flow may then be restored Clearly this is
12. something most repair techs should not attempt Some newer amps have LED indicators connected to the circuit which will turn on when the right threshold of current flow has been reached This is an improvement and almost worthy if you re willing to except resistors and lights added into your amplifier s audio path which we aren t The other advantage of this system is that it allows some amp manufacturers to avoid matching their power tubes The thinking is that adjusting the bias to each tube separately eradicates the inherent differences between the tubes by insuring that the same current flows through each one PAGE 11 EIAS US Again this has some merit but it s still not as good as using tubes that are matched in the first place because compensating for the mis match causes the push pull circuit itself to become unbalanced Two wrongs don t really make a right Some of the other recommended biasing methods such as tubes running red hot increase the bias sounds harsh and runs too cool turn it down are guesswork at best Luckily one of the great things about tube amps is that they can usually stand some abuse without causing any real harm at least not immediately But don t these alterations imply that you are second guessing the amp designer and that there s a better set of operating conditions that the designer missed but the tube sellers have discovered Now some players may like the sound of
13. their amp altered by tubes with extreme characteristics and with the bias set to help compensate But often it is the mere novelty of change that they re really responding to and when the amp goes back to the proper original way we ve seen them be far happier still Because every part in every one of our designs has been meticulously evaluated compared and stressed over no matter how seemingly insignificant it might be And with every design we look for a sweet spot where all the parameters including the bias come together to give the best sonic performance consistently and reliably Every part and voltage is important yet no one complains that these other parameters aren t available for tinkering Consider our patented Simul Class circuitry where there are two different bias voltages used for separate pairs of power tubes and changing one voltage also changes the other Great care goes into getting this just right and we think we d be asking for trouble to have it adjustable for the world to play with unless you like paying to have your amp messed up Sorry meant to say Uh your amp needed biasing If that doesn t appeal to you then merely plug a matched set of MESA tubes into one of our amps and you re ready for tone Guaranteed You d be amazed at the number of service calls we field every day that lead to a diagnosis of out of tolerance non spec tube problems To think these would be prevented by including a
14. GE 3 REAR PANEL FEATURES REAR VIEW 2 100 GROUND SWITCH 66 powerjruse LIFT 120V 6A 60Hz 510 6A BLO GROUND ust Marci TUBES 2 see ox RECTO INPUTS IN CHAN A 8 OHM Speakers 6 4 0HM Located on the Rear Panel these two 1 4 jacks are the Channel A and Channel B inputs for the 2 100 These are the inputs for pre amps and or effects depending on how you have your system wired You may drive the 2 700 with your pre amp directly or choose to come from the last effect in a chain and drive the power amp this way Either way is fine and up to your preference The amplifier is stereo offering two separate channels of amplification If you wish to use only one of its channels it is neces 58 to 1 Make sure a speaker or load resistor remains con STEM SZ N nected to a speaker jack on both channels including the unused NORMAL POWER FUSE pid one or 2 the LEVEL Control of the unused channel to zero T i T necessary because an amplifier channel receiving any amount 5 7 EL34 BLO GROUND S7 S of signal at its input will require a load at its output damage will RECTO INPUTS TUBES SEE OWNERS MANUAL RECTO INPUTS most likely result MODERN The RECTO INPUTS are wired such that when the companion Rec tifier Recording Preamp is used the circuit remains
15. HM SPEAKERS 8 OHM SPEAKERS 40HM 40HM 4 UN SHIELDED _ gt CABLE PAGE19 SUGGESTED WIRING 2 oco 9 INPUT STANDBY POWER mw GAIN e a BASS PRESENCE MASTER GUTR E OUTPUT STNE 280LO CHAN RAW 1 y FOOT N EZO SWITCH C MODERN QUA WARNING reduce risk of fre ame ype snd ing oniy Do not expose this unit 0 rain or moisture RECTO PREAMP RECORDING AMPLIFIER USE SHIELDED CABLE FOR f INPUTS amp OUTPUTS TO FX e LE UNIT S amp RECTIFIER FA a RECORDING PREAMP X MIX 0 e ums iwi 4 z 11 E AMP GROUND TOPOWER AMP EXTERNAL SWITCHES ALTEX PATCH HANDBUILT IN PETALUMA CALIFORNIA PATENTS PENDING FOR MUTE RECORDING amp SOLO FEATURES TUBES SIX12AX7 STEREO MONO FX IN lt MIDI gt OUT _ OUTPUT INPUTS LEFT RIGHT LEFT RIGHT SHIELDED CABLE AC POWER 2 ONE HUNDRED RECTIFIER STEREO os ASZ NORMAL POWER FUSE gt 120V 6A I ez sto EAN BLO RECTO INPUTS emm MODERN CHAN B SPEAKERS 40HM e UNSHIELDED CABLE gt GROUND SWITCH LIFT GROUND SENMO RECTOINPUTS SPEAKERS AN 4 OHM YZ PAGE 20 r UNSHIELDED CABLE ON TRIODE
16. 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 Then all that remains is to swap the suspect tube for a known good performer 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 perfor mance so if you can t narrow the problem down to being mode or channel specific you may 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 Occasionally an anemic driver tube will cause the amplifie
17. S PENTODES amp IRISHMEN A look into the inner workings of the Vacumm Tube With apologies to Friends and Relatives from the Emerald Isle who will make their appearance soon enough the humor which follows is dedicated to the memories of Spec McAuliff and Fae Rafael McNally two of the True Greats As their numerical references suggest the terms Diode Triode and Pentode indicate the number of elements within the vacuum tube i e two three or five All tubes also require a filament or heater which is not included the count Its purpose is to excite electrons from the cathode coating by raising the temperature such that they are able to boil out of the electron rich coating material and form a cloud of free electrons in the vacuum space surrounding the cathode Although the term filament and heater are often used interchangeably there are specific differences A filament is a directly heated cathode where cathode coating is applied directly to the heating element Examples are 5U4 twin diode rectifier and 300B triode amplifier tubes A heater on the other hand is a heating element which is separate from the cathode and is usually inserted within the tubular cathode sleeve Examples are 12AX7 twin triode amplifier and 6V6 or EL84 beam power pentode tubes In all cases this fundamental aspect of each tube s construction is clearly visible especially when the heating element is glowing red hot The cathode then would be considered the first n
18. Thus the proper cocktail waitress visible through the louvers is scantily clad so as to be all the more effective at reinforcing the attractive influence of her bar and by being located in between the door and the bar she serves as bait to lure customers past the door s negative influence Once through the door however it is the rare Irishman who actually comes in personal contact with the cocktail waitress as for all intents and purposes she like the screen grid turns out to be a vanishing illusion Yet having come this far the solid influence of the bar itself now takes over and attracts the customers to congregate having happily reached their destina tion If you re still following this and haven t lost track of the count you ll know we re still one element short of the five needed to make a Pentode This last part is a pair of beam confining shields which being negatively charged serve to direct the flow right toward the plate This is much the way a short entrance hall to the bar prevents wandering accidentally into the Men s room on the way Once at the bar though the circuit is complete and the process of soul nourishing works its ritual magic Biases having been overcome illusory nightingales having vanished the spirits truly soar and the once surly Irishmen now are filled with warmth wit and kindred friendship enjoying the music and glowing nicely with their heaters on With appreciative thanks to the inhabitants of the Land o
19. Y to the ON position If a power tube is going bad or is arcing you will see it Flip the STANDBY switch to STANDBY immediately and replace the faulty power tube and the FUSE if necessary If you see nothing abnormal as you lift the STANDBY switch it is possible that a power tube shorted temporarily and blew the FUSE If this is the case it may work again normally E To be extra safe you may want to replace all power tubes the troubleshooting tradition and save the replaced set as spares Carry along a few extra fuses for they too could be worth their weight in gold someday PAGE 7 You may occasionally experience some form of tube noise or microphonics Certainly no cause for alarm this quirky behavior comes with the territory and the Tone Much like changing a light bulb you don t need a technician to cure these types of minor user serviceable annoyances and in fact you ll be amazed at how easy it is to cure tube problems by simply swapping out a pre amp or power tube First may we suggest that you set the amplifier up on something so that you can get to the tubes comfortably without having to bend down It also helps to have adequate lighting as you will need to see the tube sockets clearly to swap tubes Use caution and common sense when touching t he tubes after the amplifier has been on as they may be extremely hot If they are hot and you don t want to wait for them to cool off try grasping them with a rag and also note that th
20. action of the bar and overcome the resistance created by the door Thus the cocktail waitress was invented Once again the idea was inspired by the vacuum tube It had been discovered in some tubes often large power types that the distance to the plate was too great to attract enough electrons past the negative influence of the control grid So another grid coil of fine wire was inserted between the first grid and the plate This was called the screen grid and carrying a highly positive charge it functioned as a bait for the plate In a properly designed power tube such as an EL84 or a 6V6 the windings of the screen grid are precisely aligned to fall in the shadow of the control grid This way the electrons responding to the pull of the screen grid are lined up in sheets as they pass between windings of the inner control grid only to find that they have been fooled Once past the control grid and drawn toward the screen grid they discover there s almost nothing there The path they re on has them aligned to zing straight through the spaces BETWEEN screen grid windings So rather than a close and personal encounter they just fly on past and once they re out that far there s no PAGE 22 ON TRIODES PENTODES amp IRISHMEN Continued zi bel stoppingthem The influence of the plate takes over and being solid metal and of the highest positive attraction it is at this final destination that the electrons congregate
21. akers to provide the most effective load and making sure that all of them are in phase will help in creating the best sound possible This is not too difficult as long as you understand a few things about loading and how to connect your speakers to provide an optimal resistive load MESA Boogie amplifiers can handle 4 and 8 ohms effectively Never run below 4 Ohms in a tube amplifier unless you are absolutely certain that the system can handle it properly this can cause damage to the Output transformer A few amplifiers can handle 2 Ohms effectively without damaging them for example the MESA S Bass 400 You can always have a higher resistance 16 Ohms for example without damaging results but too low of a resistance will likely cause problems When running a higher resistance for example 8 Ohm output into 16 Ohm cabinet a slightly different feel and response will be eminent A slight mismatch can provide a darker smoother tone with a little less output and attack This response is a result of the amplifier running a bit cooler Sometimes when using more than one cabinet a mismatch will be the only option LY RAM AER des If you have only a single speaker you just match that single speakers impedance to the amplifier and you are done In many cases you will have a number of speakers and then you must calculate the load that the amplifier will need to support There are generally three ways to wire multiple speakers together
22. ay and read this operating manual it will prove to be quite worth while in the end and will help you to enjoy your new amplifier to its full extent FRONT PANEL CONTROLS ie Each channel of the 2 700has its own LEVEL Control If the amplifier is being fed by signals from a typical pre amp try a setting of 2 as a starting point If the amp is being fed by lower level signals such as those from minus 20db type effects units etc you may need to raise the Levels as high as 2 00 or 3 00 NOTE Remember to turn the LEVEL Control to zero on any channel not con MESA nected to a speaker or load resistor A Load must be present at all times when e either channels LEVEL Control is dialed to anything other than zero Failure LEVEL A LEVELB to comply to this procedure can cause serious damage to your 2 100 s power on MODERN oy section PRESENCE POWER STANDBY PRESENCE Each channel the 2 700 has its own active PRESENCE Control These controls provide a boost in the upper mid range lower Treble zone which are the frequencies that tend to get obscurred in the energy of live performance use them when you need to cut through a loud mix MESA Use these PRESENCE Controls with discretion as they can make for some ear e damaging almost harsh sounds if set too high especially if the TREBLE Control LEVEL A e LEVEL B on your pre amp is dialed up extremely high MODERN 10 10
23. bias adjustment is something of an insult to you and us If you put the wrong size tires on your car do you think changing the pressure will make them right Please don t think this is a blanket indictment of the other guys selling tubes it isn t And their tubes aren t all bad either It just doesn t make sense to pay more of your hard earned cash for tubes that were probably made in the same Russian or Chinese factory and which have the possibility of being outside the performance window we select for your amp And it pains us to hear the hype and mystique built up around biasing when twenty five years of evidence affirms our decision to make bias circuits that never need adjustment How much money and trouble that has saved MESA Boogie players you couldn t estimate Our rigorously tested and hand selected tubes are available at your nearest MESA Boogie Pro Center or from us directly Nobody offers better price quality or warranty than we do so why swerve Next time we ll talk about our part in developing the great Sylvania STR 415 type 6L6 and how we re on the verge of seeing something fairly close reappear on the market Remember we still have some of these super rugged mondo bottles available for older amps Boogies only please Until then Relax Breathe and Nourish your soul Cheers MESA Boogie Ltd Randall Smith Designer amp President PAGE 12 SPEAKER IMPEDANCE MATCHING amp HOOK UP GUIDE Wiring up spe
24. cabinet to connect to your amplifier This is when m you need to figure out the loads and how to wire them up without applying too low of a resistance on the amplifier y ditte E amy The importance of this is more evident when you have more SPEAKER A SH e Simply connect the Positive side of Speaker A to the Posi tive side of Speaker C Connect the Negative side of Speaker A to the Positive side of Speaker B then on to the Positive side of Speaker D and finally on to the Negative side of Speaker C SPEAKER C SPEAKER D And lastly connect the Negative side of Speaker B to the Negative side of Speaker D XS S 4 Eight 8 Ohm speakers wired in Series Parallel a Total a Load of 8 Ohms POSITIVE a NEGATIVE PAGE 14 WIRING SCHEMES Partial back view of amplifier 8 OHM 4 OHM 4 OHM 8 Cabinet gg _ MESA LL 8 Ohm Cabinet Partial back view of amplifier 4 OHM 80HM 160 GN la e 16 Ohm Cabinet Partial back view of some Mesa amp 8 OHM 4 OHM 4 OHM Qe 80hm Cabinet SAFE MISMATCH PAGE15 Amplifier to Speaker Cabinets Partial back view of amplifier 8 OHM 4 OHM 4 OHM 4 Ohm Cabinet Partial back view of amplifier 4 OHM 80HM 160HM 16 Ohm Cabinet SAFE MISMATCH WIRING SCHEMES Amplifier to Speaker Cabinets Partial back view of amplifier 8 OHM 4 OHM 4 OHM la 8 O
25. dless of what tube is in the socket or even if the tubes aren t plugged in at all it doesn t change the bias voltage a bit So the end of the short answer is this Since a bias supply needs to put out the right voltage and never vary wanted to build amplifiers that were individually hard wired to the correct values and NEVER needed adjustment And for 25 years that s how MESA Boogies have been built Time to change tubes Just plug our tubes into any one of our amps and you re DONE No tech needed NO bills and no BS about biasing And most important The bias is RIGHT because it can t change Now you want the long answer Here s more information on how our hard wired bias avoids trouble Please read on But first let s make an important distinction Our business is designing and building high performance amplifiers And for this we need tubes whose variance is within a narrow range Our warehouse is full of rejects oh they work they just don t perform within our tolerance range We have a very sophisticated computer based tube testing system nicknamed Robotube that matches and measures tubes over seven important parameters It can even predict which tubes are likely to have a shortened lifetime even though they work perfectly during the test Because our business is building quality amps we can afford to reject a lot of wayward tubes The guys you hear complaining because Boogies don t have bias adjusters are primaril
26. e and for two main reasons First the Bias is set like the bar doors to allow some passage Second the grid is mostly NOT THERE like the louvered doors which are mostly open spaces Unlike the plate which is solid the grid is like a coiled bed spring It can create a repelling field but mostly it s empty space between widely seperated windings of wire It s very easy to control the electrons as they pass through the grid s force field Changing the grid voltage only slightly will have an enormous effect on how much current flows through and that s what AMPLIFICATION is a small change in voltage at the grid causing a large change in current flowing to the plate The purpose of the louvered bar doors is similar to that of the grid namely to give momentary pause while still revealing the promise within Hesitation mostly gives way to temptation but there are those few stalwart Irishmen who think twice and decide to come back later Most just pause slightly then go on through That is the purpose of the bar doors to prevent everyone from crowding in all at once and as the door is made less of a barrier wider spaces between the louvers more of the bar s attractive influence is felt outside thus amplifying the customer flow and increasing the crowd at the bar AAD Occasionally though bar doors even the louvered type were found to be too effective and too many customers turned away Something further was needed to increase the attr
27. e glass down around the bulbous silvery tip is considerably less hot which makes it easier to handle Gently rock the tube back and forth as you pull it away from its socket weed ue SHE There are two main types of tube faults shorts and noise Both large and small tubes may fall prey to either of these problems but diagnosis and remedy is usually simple If a fuse blows the problem is most likely a shorted power tube and shorts can either be mild or severe In a mildly shorted tube the electron flow has overcome the control grid and excess current flows to the plate You will usually hear the amp become distorted and begin to hum slightly If this occurs quickly look at the power tubes as you switch the amp to STANDBY and try to identify one as glowing red hot It is likely that two of a pair will be glowing since the shorted tube will pull down the bias for its adjacent mates but one tube may be glowing hotter and that one is the culprit The other two are often fine unless they ve been glowing bright red for several minutes Because there is no physical short inside the tube just electrons rioting out of control merely switching to STANDBY for a few moments then back to ON will usually cure the problem at least temporarily Watch the tubes carefully now Should the problem recur the intermittent tube will visibly start to over heat before the others and thus it can be identified It should be replaced with one from the same color
28. e 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 Be sure to have the warranty card filled out by the store at which it was purchased and return to Mesa Boogie 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 READ AND FOLLOW INSTRUCTIONS OF PROPER USAGE RECTIFIER STEREO 2 ONE HUNDRED Operating Instructions Congratulations on your choice of the RECTIFIER STEREO 2 100as your power amplifier and welcome to the MESA Boogie Family This 2 rack space uni
29. er part s of the amplifier s internal circuitry No other user serviceable parts exist in side Refer service to qualified personnel Always unplug AC power before removing the top cover of the amplifier The total power consumption for the 2 200 is 6Amps 120 Volts Thus a 15 Amp circuit which is what most house circuitry is wired with is adequate Make sure the Euro style A C power cord is firmly seated in the power receptacle before powering up the unit Always connect the A C cord to a 3 terminal grounded socket If none are available connect the A C power cord to a ground lift adaptor and then connect to a 2 terminal outlet This may also be necessary from time to time for noise problems This style of power cord will make tear downs and cable routing a lot easier and save you time as well If you amp should ever need a replacement just call and we ll be happy to send you another one for a nominal charge or visit your nearest MESA Boogie Pro Center This is the 2 200 s A C s Alternating Current main fuse and provides protection from outside A C fluctuations as well as power tube failure damage Should the FUSE blow replace it with the same rating in a slo blo type package The domestic U S version requires a 6 Amp SLO BLO FUSE A power tube short or failure is often the cause of a blown fuse Follow the cold start procedure mentioned earlier in the ON STANDBY switch section and watch the power tubes as you flip the STANDB
30. f the Leprechaun we have now concluded our little diversion into the mechanics of proper bar lay out A feature article by Randall Smith Designer President PAGE 23 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
31. gain the rule is that one device in your system and usually only one needs its circuit ground connected to its metal chassis ground all others should be lifted in other words disconnected for quietest operation Some effects units provide similar switches some are con structed such that the input ground and the output ground are permanently separated in other cases the method used to isolate the grounds is unclear Again some experimentation is vital to discovering which combination of lifted and grounded works best in your rack and our GROUND ISOLATION Switch makes this process much easier NOTE If the 2 100 is operated outside of a rack installation the switch should generally be set to the Normal position or squealing buzzing and oscillation may occur Always check this switch before thinking that something has gone wrong with your amp The 2 200 provides one 8 Ohm and two 4 Ohm speaker outputs for each channel When using a single 8 Ohm speaker or 8 Ohm cabinet on a channel connect the speaker or cabinet to the 8 Ohm jack If using two 8 Ohm speakers assuming they are wired in parallel or cabinets on a channel plug them both into the 4 Ohm jacks The logic here is that two 8 Ohm loads connected in parallel add up to a 4 Ohm total load Mismatching of speaker CHAN B CHAN A impedance will not cause damage or severe loss of power Extreme mis matches speakers 5 NM A N speakers Will decrease tube l
32. hm Cabinet 8 Ohm Cabinet CORRECT MATCH Partial back view of amplifier 8 OHM 4 OHM 4 OHM la la p CORRECT MATCH 4Ohm Cabinet 40hm Cabinet 16 Cabinet Partial back view of amplifier 4 OHM 4 OHM 8 OHM ORQ 80hm Cabinet 16 Ohm Cabinet SAFE MISMATCH Partial back view of amplifier BOHM 4OHM 4 la 9 CORRECT 16 Cabinet WIRING SCHEMES Amplifier to Speaker Cabinets Partial back view of amplifier 4 OHM 4 OHM 8 OHM 16 Ohm lm 9 SERIES BOX 80hm Cabinet 80hm Cabinet 80hm Cabinet SAFE MISMATCH E Partial back view of am a aa CORRECTMATCH som som Q Q 9 Qo 16 Ohm Cabinet 16 Cabinet SAFE MISMATCH 16 Ohm Cabinet 16 Ohm Cabinet PAGE17 WIRING SCHEMES Amplifier to Speaker Cabinets Partial back view of amplifier 4OHM 40HM la 8 Cabinet 80hm Cabinet 16 Cabinet SAFE MISMATCH 16 Cabinet 16 Ohm Cabinet 16 Ohm Cabinet SAFE MISMATCH PAGE18 WIRING EXAMPLE 1 Mesa Boogie all tube Formula Pre Amplifier ESA BOOGIE PENDING FX SEND RETURN L j amp 10 e HR GROUND FX MIX E lim W HANDMADE IN CALIFORNIA 24 V VEZ 2 100 ALL TUBE STEREO POWER AMPLIFIER GROUND l N SMIGH SWITCH n nonw NORMAL POWER FUSE NORMAL C T 120V 6A S 60Hz SLO 6A e RECTO INPUTS MUST MATCH TUBES SEE OWNERS BOOK HEGTOIN INPUTS 80
33. however as the push pull becomes unbalanced Whenever you are trying to diagnose a suspect tube keep your other hand on the POWER and STANDBY switches ready to shut them off instantly in the unlikely case you provoke a major short If you think you ve located a problem tube but aren t sure we recommend substituting the suspect with a new one just to be sure of your diagnoses You will be doing yourself and us a big favor by just following the simple guidelines previously mentioned regarding tube replacement You ll probably be successful with much less effort than is required to disconnect everything and haul the unit to a technician who will basically perform the same simple tests If the tubes are still within their six month warranty period we will happily send you a replacement Just note the color designation on the tube label so that we can send you the appropriate match PAGE 8 AC eibi uai uae A Because your amplifier is an all tube design it is quite possible that you will at some point experience 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 Let us begin by saying It is a very 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 take many forms but can generally be described in two catego ries Noise and Microphonics
34. ife however MESA Boogie 4x12 and 4x10 cabinets come fe A0 EN fa 40m Standard wired to 8 Ohms and are wired in series parallel e e e Some Non MESA 4x12 cabinets are wired 16 Ohms using four 16 Ohm speakers By wiring all four speakers in parallel you can reduce the cabinet to an impedance load of 4 Ohms assuming the speakers are 16 Ohms each Further back in this manual we have included a number of possible wiring schemes amps to cabinets that may be of some use to you when considering how to configure your rig PAGE 5 REAR PANEL Continued ize HUE NOTE If you opt to use only one channel of the 2 100 with speakers connected to that channel s output only you must turn the unused channel s level control to zero Otherwise the channel will be operating without a load and damage to the tubes and or the transformer will result The power tubes used in the 2 200 are MESA Boogie STR 430 type 6L6 GC s These tubes have been tested in the amplifier during several burn in periods before leaving the factory You can expect 6 months to 2 years or more of outstanding performance from your MESA Boogie power tubes depending on use Tube wear is gradual and usually goes unnoticed until new replacements are installed Worn power tubes tend to sound flat with reduced punch clarity and high end Occasional loss of power or sporadic blowing of fuses is nearly always caused by troublesome power tubes e Often
35. l out high gain crunch or lead sound Players that use mostly these types of sounds may prefer the EL34 clip to the 6L6 s that come standard in the 2 700 If you need a variety of sounds and rely on a clean chording sound much of the time you will likely prefer the stock compliment of 6L6 s that the 2 700 comes fitted with We feel the 6L6 is a more balanced sounding tube that produces plenty of harmonic lushness while at the same time delivering the rich lows that are crucial to both a warm clean sound and huge tight high gain crunch sound PAGE 4 REAR PANEL Continued We recommend the 6L6 for reliability In our many tests and continued use of the currently available EL34 type power tubes on the market today we regret to say that they do not appear to be as rugged in construction as the available 6L6 This is another reason why your 2 200 was shipped with 6L6 power tubes If you plan to use the EL34 s we suggest that you keep a full set of tubes and extra fuses with you during all performances in the event of a tube failure occurring when using the currently available EL34 s This mini toggle switch is extremely useful in reducing the hum and buzz caused by ground loops which occur in rack installations Ground loops occur when there is more than one path for grounds between electronic units There are three main type of ground loops each one contributes its own trademark component of buzz or hum The three types of ground loops are
36. light 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 9 BIAS ADJUSTMENT part of a continuing series BEAM CONFINING An Article written by Randall Smith ELECTRODE CATHODE GRID SCREEN GRID H gt PLATE Here s a question we often hear Why doesn t MESA put bias adjustments in their amplifiers Structure of a 6L6 5881 Beam Power Pentode Well there s a short answer and a long answer to this question The short answer is that during my 12 years of repairing Fenders one of the most frequent problems saw was bias controls that were either set wrong or that had wandered out of adjustment due to vibration As any honest tech will tell you there s lot s of easy money to be made by sprinkling holy water on amplifiers uh what meant to say is Your amp needed biasing See what mean What customer is going to argue with that It only takes a moment and a volt meter The Fender diagram shows how Adjust this trim pot for 52 volts That s it Nothing more Now don t be fooled into thinking that tubes draw more or less bias they don t The way a bias supply is connected to a tube is akin to a dead end road it just trails off to nowhere without really completing a circuit It s a static voltage and regar
37. modern rock FRONT VIEW 2 100 9 o D HEEL Mm 1111111111111 LEVELA LEVEL B ON MODERN ON i e PRESENCE POWER STANDBY PRESENCE REAR VIEW 2 100 GROUND SWITCH BIAS 8L6 powerjruse LIFT 120V 6A SLO EL34 6A BLO GROUND MUST TUBES 51 SEE OWNERS BOO RECTO INPUTS 8 OHM SPEAKERS S uc SPEAKERS PAGE 1 eL PM Without further delay connect up your favorite preamp and get ready to experience one of the most commanding sounds in rack mount history as Recto power goes stereo for the first time in this amazing package NOTE BEFORE YOU MOUNT THE 2 100 IN YOUR RACK This is an extremely aggressive and powerful amplifier intended for use with one of the above mentioned MESA preamplifiers in large venues If after trying it you feel you may have chosen more amp than you need you may find one of the more forgiving MESA strereo power amplifiers such as the Stereo 2 50 or the Stereo Simul Class2 90 more suited to your style or application Save the packing material and keep the amplifier in perfect condition and you should be able to return it to the place of purchase for full credit toward one of the less aggressive models that might perhaps better suit your needs If this stunning agressive power well suits your playing style and needs congratulations and by all means rock on And now on to the controls and features of your new 2 100 Please take some time along the w
38. r to sound flat and lifeless but this is somewhat uncom mon as worn power tubes are a more likely suspect for this type of problem 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 ATATIME 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 Remember take your time be patient and chances are real good that you can fix your amp you
39. rage but the analogy makes it easy to visualize the loosely bound electrons dissolved in the rich cathode coating as they effervesce from its heated surface But back to the electron flow If the electrons are strongly attracted to a positively charged plate then it follows that they are strongly repelled by a negatively charged plate and they are Thus if an alternating current such as comes from a transformer is applied to the plate electrons will flow only during the times when the plate is positively charged During periods of negative plate charge electron flow is stopped and the space charge of electrons remains compressed in the area around the cathode PAGE 21 ON TRIODES PENTODES amp IRISHMEN Continued Thus a diode tube one with a cathode and an anode is mostly used to rectify alternating current into direct current by passing it without a cathode and an anode is mostly used to rectify alternating current into direct current by passing it without restriction but in one direction only This also explains why closing time is stricly enforced at Irish pubs During normal operation the traffic flow is similarily unimpeded and uni directional toward the bar and this process rectifies the work day negativity It goes without saying that no one leaves as long as the atmosphere around the bar remains positively charged This section is a continuing technical treatise on the workings of Irish Pubs but to make it easier for the la
40. rself by finding and replacing the bad tube It kills us to see someone who has shipped their amp back to us and all it needed was a simple tube replacement If you must send back your amp unplug the power cord speaker and reverb cables then remove the chassis from the cabinet by unscrewing the four mounting bolts on top The chassis then slides back like a drawer and comes out Remove the big power tubes and mark them according to their location from left to right 1 2 etc They need to be wrapped separately with plenty of wadded up newspaper around them and put in a smaller box within the larger carton To wrap the chassis use plenty of tightly 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 s
41. ssary Avoid excessive wiggling of the tubes when removing or installing them as it can break off the small plastic key which insures correct orientation of the tube in the socket Make sure you check out the sections on Power Tube and Pre Amp Tube maintenance located further back in this manual Some helpful tips on prolonging the life of your amplifiers tubes makes these maintenance sections worthwhile reading The three small tubes are type 12AX7A also known as 7025 or ECC83 These tubes are very long lasting and trouble free in the 2 700 should they ever need replacement due to a specific malfunction genuine MESA replace ments are recommended for best performance NOTE You must remove the top cover of the chassis in order to gain access to the driver tubes These tubes can become quite warm Allow them to cool down before changing and its always a good idea to power down the unit when changing any of the tubes 4 Y Also be aware that some of the circuitry components namely the large round capaci GENTLY ROCK TUBE BACK AND FORTH WHILE tors running parallel to the three driver tubes will store a substantial amount of elec e RE trical charge even after the amplifier is powered down For safety reasons be sure PAGE 6 REAR PANEL Continued pulsu ERASMUS to grab hold of the particular pre amp tube when replacement is required Do not allow your fingers hands or rings jewelry to come into contact with any oth
42. t is born of legendary stock and traces its lineage to the mighty Dual Rectifier Solo Head Here the stunning performance of the Dualis faithfully recreated in a stereo format that duplicates the power section exactly when the Dualis set to its Silicon Diode rectifier setting Rectifier tubes were not included in this package as their size did not permit inclusion along with an overall consensus among players asked that those needing 200 watts of this type of aggressive power would require the tighter faster response of the silicon diodes The eight 6L6 power tubes 4 per side are fan cooled and kick out 100 watts of all tube power per channel Three 12AX7s make up the driver section and these are housed inside the unit Preamp tubes used in this manner rarely wear out as there is little or no exposure to excessive vibration and they are operating under minimal gain require ments The RECTIFIER STEREO 2 100 is a smart power amplifier as it contains the MODERN Switchable Voicing feature It responds to a trigger pulse sent by either of its companions the Rectifier Recording Preamp or the TriAxis Programmable Preamp When a cable is connected to the MODERN trigger port and this feature is switched via any tip to ground type logic the negative feedback in the power section of the 2 710015 reduced unleashing a sound of true ferocity This is a trademark sound in the Dualand Triple Rectifier Solo Heads and has become the most recorded sound in heavy
43. umbered element because it is the source of the electrons The word itself is from the Greek literally meaning completely down which implies a sense of central origin like the center of the earth where Tone begins It might be said that an ecstatic audiophile experiences a positive catharsis his soul being purified when his system transports him to Audio Nirvana The only trouble with taking this positive imagery too far is that the cathode is unfortunately negative at least electrically speaking However this is easily remembered since virtually all musicians and audiophiles have also experienced the more common negative catharsis when they emerge from the emotional rebirth kicking and screaming in rage and frustration Once heated the intrinsically negative electrons are energetic little fellows of almost no mass Thus they may be accelerated almost instantaneously and will travel through a vacuum a nearly the speed of light Being of like negative charge they tend to repel one another and thus within the electron cloud surrounding the cathode there is much jostling and elbowing as each one tries to maintain his distance from all the others unless there is a strong and universal attraction from an outside influence Visualize if you will a group of sub atomic Irishmen milling about and in a repellent negative state of mind All are scowling and none wants to have anything to do with the other Now introduce a strong attraction say a public
44. y in the business of selling tubes not amps They don t want to throw away 30 percent of their inventory so they promote the idea that tubes outside our parameters can be used to customize amplifiers and they criticize us because our amps can t be adjusted to accommodate their out of MESA tolerance tubes Now you might be thinking But thought you just said that tubes don t bias therefore they don t effect the bias supply and thus it doesn t need to be adjustable When you set the bias whether it s by selecting the right resistors as we do or adjusting a trimmer which is quicker what you are doing is establishing the correct amount of idle CURRENT that flows through the power tubes But you can t adjust the current directly you can only change it by adjusting the amount of bias VOLTAGE that goes onto the tubes control grids PAGE 10 IESUS US Voltage and current are NOT the same Current is the AMOUNT of electricity the quantity and is measured in amperes Voltage is the degree of electric charge like the pressure to use the old water analogy Let me illustrate how different voltage and current are When you scrape your feet across a carpetted floor in dry wintery conditions your body can become charged with 50 000 to 100 000 volts of static electricity And when you reach for the door knob a spark jumps and you feel it The voltage is super high but the current measured in micro amps is tiny
45. y may have a chance to warm up before being put to use Before the power is switched on make sure the STANDBY switch is in the standby position gt a E And as mention above wait at least 30 seconds before changing to the ON position ENGINEERING VEL A LEV MODERN LYTI ENCE POWER STANDBY PRE This jack is the trigger port for the auto tracking MODERN feature This jack can receive a trigger pulse from the corresponding jack on the MESA Rectifier Recording Preamp Ot Triaxis Programmable Preamp This smart power amp auto modifies the amount of negative feedback in the power section when the MODERN mode in Channel 2 of the Recto Preamp is selected or switched to via the Footswitch The Front Panel LED indicates when the feature is active and negative feedback has been reduced rm If used with the Triaxis use one of the 4 programmable switch Neue Sn rs S Sick a ON MODERN oN jacks and store under a user preset This reshaping is crucial to the ee o sound of the MODERN mode and using this feature duplicates the recto mpurs werte RECTO INPUTS se circuit and the performance of this punishing mode in the Dual amp CHAN B of CHAN A Triple Rectifier Solo Heads SS soni NOTE Use unshielded cable of good quality when connecting the MODERN trigger port to your preamp or master switching unit Shielded cable will also work but is unnecessary PA
46. yman to understand it is explained in terms of vacuum tube technology Enter the original bar free beer and no doors Well it turns out that some control over the flow can be a necessary and useful advantage This led to the invention of those swinging louvered saloon doors which are open at the top and bottom They are patterned after the control grid of the vacuum tube which is a loosely wound coil of thin wire located between the cathode and the plate In a Triode the plate is always positively charged with high voltage D C and even though the grid is blocking the path those negative electrons can still FEEL the strong attraction just as the Irishmen can see in through the louvers of the bar doors They know what pleasures lie beyond but to get there requires overcoming the negative influences controlling the access This negative influence is typically called a Bias In electronic terms that means the grid is supplied with a voltage which is slightly MORE NEGATIVE than the already negative electrons The more negative the Bias the more it tends to neutralize the attraction of the plate and repel the electrons back toward the cathode The Irish can be similarily charged with Bias but unless you are Irish yourself this type of Biasing may be more difficult to understand The effect is similar though The more negative the Bias the more it impedes forward progress Generally speaking though the electronic Bias of the grid is easiert to overcom
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