Mesa/Boogie RECT-O-VERB 50 User's Manual
Contents
1. Oi SE O10 e 230 2 Q Sy cc lt lt Oe a a 152 5 22 2 2 Gy lt lt ui a gt 2 205 a LLI Gy cc lt I lt Oe a a 2 cc lt I lt ui E a a gt 2 5 PAGE 13 LLI lt 2 5 lt 7 gt 5 2 OM wi 2 ss Oo LLI QA MASTER PRESENCE a u 2 Gy lt lt a 1 2 2 gt Zx e gt a ae 7 z sOi O 9 gt 2 gt Gy oc lt I lt a 502 2 5 z 8 9 lt 4 ui oe a gt 5 PAGE 14 LLI lt 2 oS 77 2 ON wi gt 8 Oo LL e Oi SE O10 e 230 2 Q Sy cc lt lt Oe a a 152 5 22 2 2 Gy lt lt ui a gt 2 205 a LLI Gy cc lt I lt Oe a a 2 cc lt I lt ui E a a gt 2 5 PAGE 15 NOTE POWER TUBES ARE HOT BEFORE CHANGING RECT O VERB SOLO 50 TUBE TASK C2. drenched solo work in both of the Lead 10 5 Modes Simply run the control little higher than that of the top channel FX MIX RETURN SEND 9 CHANNEL SELECT This switch simply allows you to switch between the two channels RHYTHM and LEAD without using the Channel Select Footswitch or when one is not available To use the footswitch however the Channel Select switch must be in the up SET RHYTHM RHYTHM position WHEN USING FOOTSWITCH RHYTHM LEAD PAGE 9 FACTORY SANPLE SETTINGS HEAD VERSION SHOWN NAH Sparkling Clean SOLO OUTPUT RHYTHM MASTER PRESENCE BASS MID EN N A 2 A yes Pushed Bluesy Rhythm Solo Both Channels e MASTER PRESENCE BASS MID SOLO OUTPUT LEAD Blues Lead Both Channels 8 e MASTER PRESENCE BASS MID SOLO OUTPUT c9 LEAD 57 171 18 2 8 High Gain Lead Crunch Both Channels SOLO OUTPUT RHYTHM MASTER PRESENCE BASS MID 9 9 LEAD PAGE 10 TREBLE O 7 GAIN GAIN CLEAN PUSHED CLEAN PUSHED VINTAGE MODERN CLEAN PUSHED VINTAGE MODERN CLEAN PUSHED VINTAGE MODERN X S FT SW A FT SW A 225 FT SW 225 A FT SW INPUT INPUT INPUT INPUT FACTORY SAMPLE SETTIN
3. 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 Guaran teed 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 bias adjustment is something of an insult to you and us If you put the wrong size tires on your car do you thi
4. 792 pt 610120 pt 592148 RHYTHM CLEAN la la FT SW INPUT SEN 9 PUSHED 5 MASTER PRESENCE BASS MD TREBLE GAN VINTAGE ama OD LEAD MODERN KNOBS pt 592739 JACK pt 40811 CONTROL CONTROL pt 610123 SWITCHES 592150 pt 607101 CONTROL POWER STANDBY CONTROL SWITCHES pt 592739 pt 592737 pt 607101 ALL CONTROL KNOBS Pt 408110 JACKS ALL 3 JACKS FUSE 610111 pt 618100 pt 790347 MESA BOOGIE RHYTHM WHEN USING fuse oF removing RHYTHM Pamaen 000000 MN MN MM SO 10 400 kara OUT POWER FUSE ase ae FXMX RETURN expose this unit to rain or moisture uemeenmc serving to qualified personnel 25 JACK AC RECEPTACLE cane CONTROL pt 618100 pt 613713 602112 pa 592736 PAGE 22 M ESA BOOGIE T he Spirit of Art in Technology Thank YOU for trusting MESA Boogie to be your amplifier company We wish you many years of toneful enjoyment from this handbuilt all tube instrument T he Spirit of Art in T echnology REESE 1317 Ross Street Petaluma CA 94954 USA Phone 707 778 6565 FAX 707 765 1503
5. ELECT TOGGLE FACTORY SAMPLE SETTINGS PAGE PERSONAL SETTING PAGE TUBE TASK CHART TUBE MAINTENANCE SPECIAL ARTICLE REGARDING TUBE BIASING By Randall Smith PARTS SHEET 3 4 4 4 5 5 6 7 6 9 10 11 12 13 14 15 16 17 18 19 20 Your MESA Boogie Amplifier isa professional instrument Please treat it with respect and operate it properly USE COMMON SENSE AND ALWAYS OBSERVE THESE PRECAUTIONS Do not expose amplifier to moisture rain or water 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 Insure adequate air circulation behind amplifier 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 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 Remove the power plug from the AC mains socket if the unit is to be stored for an extended period of time Do not use solvents such as benzene or paint thinner to clean the unit Wipe off the
6. GS COMBO VERSION SHOWN Sparkling Clean CLEAN la pager GAIN TREBLE MID BASS PRESENCE x INPUT MODERN Pushed Bluesy Rhythm Solo Both Channels CLEAN PUSHED GAIN TREBLE MID BASS PRESENCE VINTAGE MODERN 27 11 84 Blues Lead Both Channels CLEAN Wy PUSHED GAIN TREBLE MID BASS PRESENCE ee VINTAGE 4060906 MODERN High Gain Lead Crunch Both Channels CLEAN 216 9 WZ GAIN TREBLE MID BASS PRESENCE VINTAGE 9 9Z MODERN PAGE 11 MASTER MASTER MASTER RHYTHM RHYTHM RHYTHM OUTPUT OUTPUT OUTPUT OUTPUT LLI 5 a ne OO 20 H 2 a gt 52 T LLI Qa Z a 71 Q F SZ lt lt ui a oak gt 2 a gt O10 N 27 i Z z 2 ui 5 a a gt z 5 O10 O O ZS gt amp I Q SZ i 8 lt lt w ui BE a 502 gt OHO O10 O10 X s AZ u lt lt GE a E 502 gt O O 030 010 PRESENCE PAGE 12 LLI lt 2 oS 77 2 ON wi gt 8 Oo LL e
7. HART TUBES TURN POWER SWITCH TO OFF AND LET COOL TUBE NOISE amp MICROPHONICS 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 the 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 the 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 DIAGNOSING POWER TUBE FAILURES 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 e
8. M ESA BOOGIE 5010 gt 0 RECT 0 VERB 20 Owner s anual T he Spirit of Art in T echnology 1317 Ross Street Petaluma CA 94954 Greetings From The Home Of Tone 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 an amp bred of fine all tube heritage benefiting from the many patented pioneering Mesa Boogie circuits Feel confident as we do this amp 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 SINGLE 226007 SERIES Table of Contents PRECAUTIONS OVERVIEW INSTANT GRATIFICATION 3 DEMONSTRATION SETTINGS CHANNEL MODE SELECT RHYTHM CHANNEL CLEAN amp PUSHED LEAD CHANNEL VINTAGE amp MODERN CONTROLS GAIN TREBLE MIDDLE BASS PRESENCE MASTER OUTPUT CONTROL SOLO CONTROL TOGGLE SWITCHES STANDBY POWER BACK PANEL AC RECEPTACLE FUSE SLAVE OUT SPEAKERS FX LOOP SEND RETURN MIX REVERB RECT O VERB COMBO amp RECT O VERB HEAD CHANNEL S
9. amp HEAD PAGE 1 gt 1 N RHYTHM N 7 2 ier not ur shoo serv Servi FRONT PANEL First familiarize yourself with the layout of the Front Panel Next remove the footswitch from the transport pouch located inside the cabinet combo and connect it to the proper jack RECT O VERBS use a DIN jack located on the rear of the chassis directly behind the label FOOTSWITCH SOLO 50 HEADS use a 1 4 jack on the right side of the Front Panel If the footswitch is not available you may select the two channels via the manual Channel Select toggle located on the far left of the Rear Panel RHYTHM 09 ON ON Evy SEN PUSHED Rec MASTER PRESENCE BASS TREBLE GAIN VINTAGE ee 5 2 LEAD MODERN SOLO 50 HEAD VERSION First remove the protective covers from the tubes plastic webbing before connecting the A C cord to a power receptacle Connect your favorite guitar to the instrument INPUT jack Flip the POWER switch to the ON position while leaving the STANDBY switch set to STANDBY It is always a good idea to practice this start up procedure as at least 30 seconds of warm up time lessens the shock on cold power tubes thus prolonging their life substantially Next using the example below as a guide set the controls as illustrated and flip the STANDBY switch to the ON position to listen to the
10. ave 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 primarily 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 do
11. ch channel of your amplifier contains two different Modes of operation that may be selected depending on your application In this way you may decide to use the channels for their most obvious sounds or with the flick of a switch invert the channels for the opposite sound style The voicing of the modes is accomplished by rerouting and reconfiguring the circuit in both pre amp and power sections of the amplifier Here are the choices CLEAN RHYTHM Top Channel CLEAN toggle up delivers a sparkling rendition of the classic black face style rhythm sound with the added HEAD VERSION dynamic response of the RECT O 5075 super quick driver circuit This is a low gain mode that is optimized for fast clear attack huge breathy low end response and the impression of headroom far in excess of the conservative 50 watt rating It may also be cranked to produce a vintage style clip when the GAIN control is maxed that is relatively uncolored when compared to the PUSHED sound This is preferable when you wish to retain more of the guitars natural character and don t need thick saturation PUSHED toggle down adds substantial gain by saturating another tube stage and revoicing the treble frequencies to respond much better with overdriven sounds A by product of adding this extra gain is a masking of some of the sparkling highs which lends a sort of natural tube compression making PUSHED an alternate and quite amazing lead mode along wit
12. 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 TUBE NOISE 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 12 75 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 probably found the problem To confirm a noisy power tube merely put the RECT O on Standby remove it from its socket and turn it back on It will cause no damage to run the RECT O briefly with one power tube missing You may notice a slight background hum 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 l
13. e amount of Mid and Bass that would be possible in the mix Set low the TREBLE becomes the recessive control and a warmer darker blend is produced Dial with care Subtle tweaking of this control tends to produce the best results TREBLE GAIN HEAD VERSION The MID control determines the blend of midrange punch and boldness It also has a great deal to do with how a sound feels to play Setting the Midrange low scoops the attack making the sound and feel more liquid and resilient Setting the MID control higher introduces more punch and authority helping sounds cut through a mix better Setting the Mids very high may make the strings feel a little stiffer and less spongy Keep this in mind when dialing up your sounds so that you can retain the best feel on the strings allowing you to always play your best In the PUSHED Mode the MID control set low produces a sweeter smoother clip and really allows this sound to purr Try the GAIN control set at around or so and the MID control set at around to for a tasty blend of smooth dynamic overdrive Add Treble to focus the attack and fatten with the BASS control Presence will Open up or compress this beyond vintage sound that howls with authenticity This MID TREBLE has to be one of the best sounds in the RECT O 50 NEAD VERSION At high Gain settings in either the Vintage Orange or Modern Red Modes the MID control dials in punch and aggression For the tightest crunch c
14. e been provided two 4 Ohm and one 8 Ohm to ensure the proper impedance match to many types of speaker enclosures The other features will prove to be quite valuable to you and further along in this manual they are covered extensively FRONT VIEW HEAD VERSION SOLO HEAD 50 Instant Gratification Demo Settings CLEAN RHYTHM MASTER PRESENCE BASS MID TREBLE GAIN WZ WZ VINTAGE FT SW INPUT POWER STANDBY OUTPUT amp 6 MODERN SOLO HEAD 50 ALL TUBE AMPLIFIER 5 BOOGIE HANDBUILTIN PETALUMA CALIFORNIA 4 SET TO RHYTHM EFFECTS LOOP te 4 WHEN USING kandi ee RHYTHM gt gt SLAVE O i ee 2 POWER FUSE Yi moisture LO FXMIX RETURN SEND 8 OHM 4 OHM 4 OHM OUT NDI A 120 50 60 Hz LEAD 883 AND OTHERS PENDING REAR VIEW HEAD VERSION FRONT VIEW COMBO VERSION RECT O VERB 50 4 EN ON ON SEIT PUSHED PY 24 GAIN TREBLE MID BASS PRESENCE MASTER PIX Y VINTAGE OUTPUT 0 STANDBY POWER LEAD MODERN CLEAN REAR VIEW COMBO VERSION RECT O VERB 50 WARNING MESA BOOGIE SET TO RHYTHM II IIIIIIIIIIIIIIIIII III FOOTSWITCH POWER FUSE FT SW 10 100 V 25A ai BOHM 40HM 2010 FXMIX RETURN SEND 50 60 Hz 1510 25 IBLO PATENTED 4 211 893 AND OTHERS PENDING FT SW LOCATED UNDER CHASSIS RECT 0 VERB COMBO
15. ecause 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 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 something most repair techs should not attempt Some newer amps have LED indicators connected to the circuit which will turn on when the right
16. exterior with soft cloth Be sure to have the warranty card for this product filled out by the store at which it was purchased and return to Mesa Engineering 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 FOR PROPER USAGE SINGLE 260007 SERIES Table of Contents Congratulations on your choice of the SINGLE RECTIFIER 50 You have purchased a handbuilt instrument of the finest quality and craftsmanship A unique blend of yesteryears black magic power section design combined with our race shop approach to finely tuned high gain pre amp circuitry leaves the RECT O 50 standing alone instantly a classic destined for vintage status With two channels housing four definitive and distinctly different Modes a complete array of amazing guitar sounds can be obtained quickly and easily Looking to the Rear Panel assures that all your interfacing needs are covered A Parallel Effects Loop with a MIX control provides tone insurance for even those questionable effects To use the SINGLE RECTIFIER 50 in larger rack systems or to interface to other power sections the SLAVE jack and is a welcome feature Two speaker jack combinations hav
17. h 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 WARNING Unplug power mound ing This style of power cord will make tear downs and cable routing a lot easier and save you time as well If you 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 FUSE 120V 25 50 60 Hz SLO 25A IBLO This is the 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 2 5 amp Slo Blo fuse A power tube short or failure is often the cause of a blown fuse Follow the cold start procedure mentioned in the ON STANDBY switch section and watch the power tubes as you flip the STANDBY switch to the ON position HEAD VERSION WARNING Unplug before replacing fuse or removing bees 5 mou ling POWER FUSE 120V 25 50 60 Hz SLO 25 BLO HEAD VERSION This 1 4 jack provides a signal derived from the speaker jack Perfect for us
18. h its obvious crunch rhythm potential LEAD Bottom Channel VINTAGE toggle up is the creamier warmer sounding of the RECT O S two lead modes and therefore excels at single note solo sounds by producing a rounder attack with more elasticity as the notes decay Often first misinterpeted by short demos this mellower blend becomes many owners favorite sound as they explore the ever changing harmonic content and precious attack envelope MODERN toggle down is emphasized attack This is by far the most aggressive forward in your face soundin the RECT O S quiver of modes By stripping negative feedback from the power section and revoicing the pre amp to respond with a more urgent feel in the time domain a beast is unleashed and the amp that was moments ago singing with a sweet languid voice becomes downright dangerous MODERN HEAD VERSION NOTE It is normal to hear a volume increase when the MODE SELECT is toggled between the VINTAGE and MODERN Modes the LEAD channel This is a result of the substantial change in power section sensitivity as negative feedback is removed and applied with the change in modes Like most amplifiers the GAIN control in each channel determines its sensitivity and overall tonal characteristics It meters the amount of Gain that your guitar signal will produce In the RECT O 50 we paid special attention to the amount and frequencies of gain present in eac
19. h mode making sure the whole range of available gain is musically usable We also worked diligently with our suppliers to develop pots with tapers useful to players that require that touch sensitive relationship of input signal level to gain saturation An essential ingredient to a great amps expressive nature To maximize your expression spend time learning the different regions of the GAIN control in each mode and tonal colors they enhance Almost more or certainly equal to the tone controls the GAIN control shapes your sound CLEAN i an PUSHED VINTAGE FT SW INPUT y A As a general guideline the lower regions of this control produce brighter tighter faster W sounds with enhanced dynamics the higher the GAIN control setting the warmer fuller more saturated and more compressed less dynamic the sound becomes Remember HEAD VERSION that with this sensitive control the entire character of the channel is determined Because the RECT O 50 is a hyper tuned gain machine some of the best and most musical sounds are found in the middle ranges of this control In other words more is not always better PAGE 3 CONTROLS Continued As with most guitar amplifiers the TREBLE control is the strongest of the three rotary tone controls Its setting on the RECT O 50 determines the blend and strength of the MIDDLE and BASS controls Set high it is the dominant control thus minimizing th
20. hording set the MID control high say around To make single notes feel juicier and more liquid reduce the MID control to around or so In the Modern Red Mode using the Mid higher and in conjunction with the PRESENCE control also set high delivers a down right ugly crunch that s huge and angry not fit for the meek This setting also sounds great and becomes easier to play and more elastic feeling with the GAIN control set at or higher This control blends in the lower frequencies and its effectiveness again depends on the setting of the TREBLE control It should be set with moderation as extreme settings in either low or high directions can produce an unbalanced tone Be especially careful in higher Gain settings of either channel Too much Bass will cause a flabby unfocused sound 6 gt Try seiting the BASS control to for clean sounds in the clean Mode and or below when dialing up high gain overdriven sounds in this Mode In the LEAD Modes try setting the BASS somewhere between BASS MID and These settings will vary with the amount of Gain and Treble you have dialed up HEAD VERSION PAGE 4 CONTROLS Continued These are controls that work in the power section to reduce attack and brightness They work on a different frequency than the TREBLE control and depending on the mode chosen and the amount of Gain dialed up can sound higher or lower than the Treble frequency Treble and Presence until the desired b
21. ing 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 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 b
22. ing the RECT O 50 as a master pre amp or additional power amps may be connected for more power when needed Some players use this to derive an FX Send Signal and go to other amps for their wet sound 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 To be extra safe you might want to replace just the adjacent tube or all power tubes in the shotgun troubleshooting tradition and save the replaced set as spares Spare fuses are a must for the fabled cord bag along with your spare tubes Always carry both for they could be worth their weight in gold someday WARNING Unplug power before replacing fuse or removing bolts mounting SLAVE chassis e NG OUT POWER FUSE 120 V 25 50 60 Hz SLO 25 BLO HEAD VERSION NOTE Once a signal is taken from the SLAVE it can not be inserted back into the FX Loop Return jack or a feedback loop will occur Much like holding a microphone into the PA system s cabinets a loud high pitched squeal will occur PAGE 8 Sensitivity to speaker mismatching in regards to ohmage differences is low hence no damage to the amplifier will occur However very low ohmage loads will cause the power tubes to
23. ir 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 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 trouble shooting process a little more intimidating it is still possible to cure the problem yourself NOTE Itis 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 18 DIAGNOSING PRE AMP TUBE PROBLEMS NOTE Anarticle written by Randall Smith that CONFINING we thought you might find interesting CATHODE ELECTRODE GRID 5 EN Here s que
24. ise 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 Then refer to the TUBE TASK CHART found on page 14 and it 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 amplifier 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 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 tha
25. l 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 17 DIAGNOSING POWER TUBE FAILURES 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 categories 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 Microphonic no
26. lectron 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 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
27. lend is reached When you have high gain or distortion sounds dialed up you will find it very helpful in darkening and compressing the sound for single note work Set the PRESENCE BASS PRESENCE control low and this compression will also focus the notes and omit any unwanted buzzy frequencies For high gain chording try higher settings of the PRESENCE control to bring out the harmonic In the RHYTHM mode it dials in sparkle and shimmer letting clean sounds cut through better Balance the haze In the LEAD channel the Presence circuitry is quite advanced because it switches from one type of Presence located in one part of the power section to a different Presence circuit located earlier in the pre HEAD VERSION amp section This switching makes the complete transformation possible that delivers the VINTAGE Mode authentically and the Modern high gain Mode absolutely over the top In the Vintage Mode the Presence is similar in strength and frequency to that of the Green RHYTHM channels CLEAN Mode Set low it warms up single notes til they purr At high settings it adds bounce and improved dynamics that can really help when you want to back your guitar volume down and clean up for rhythm playing When the Red Modern high gain Mode is called up the PRESENCE control makes the move to a new place in the circuit and gets revoiced to work on a lower frequency Just right for adding attack and urgency this Presence is the aggressi
28. n t draw bias therefore they don t effect the bias supply and thus it doesn t need to be adjustable And that s right Tubes don t effect the bias setting but the bias setting does effect how the tubes work But HOW it effects the tubes is difficult to measure 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 19 BIAS ADJUSTMENT Continued 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 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 th
29. n but the setting here does affect the channels Send strength We have found the middle ranges through to be vary well behaved for most effects Setting the MASTERS in MASTER PRESENCE this region should make for trouble free effects interlacing when using the loop HEAD VERSION PAGE 5 CONTROLS Continued OUTPUT This control determines the overall output volume level of the amplifier After the GAIN controls have been set for the desired sound style and the two channels levels have been balanced with the channel MASTER controls the OUTPUT control allows you to change the playing level by adjusting a single control The OUTPUT control is also wired as the Effects Loop Return Level control Should you ever use your RECT O 50 as a power amp alone by inserting a signal into the RETURN jack the OUTPUT control will serve as the master level control NOTE When using the EFFECTS RETURN as an input to use the RECT O 50 as a power amp the SOLO control can be used to attain a footswitchable boost if the Footswitch is connected It is wired in SOLO OUTPUT parallel to the OUTPUT control and therefore also controls the volume of the power section NOTE The Effects Loop RETURN jack can serve as a power amp input so that you may use your SINGLE 7777 VERSION RECTIFIER as a power amplifier for either stereo reproduction or to incorporate additional pre amps While the possibilities for this type of application are virtually limi
30. nk 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 6 6 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 21 FRONT VIEW HEAD VERSION CONTROL CONTROL CONTROL pt 592738 pt 592148 pt 592148 BOTH SWITCHES CONTROL CONTROL CONTROL JACK pt 601073 CONTROL pt 592737 pt 592378 pt 592
31. oduces for a source that is unusually weak it is there if you need it Simply select the LEAD channels MODERN mode The PRESENCE control will not have any effect on the sound as it switches with the mode change to an earlier stage in the pre amp 5 The EFFECTS MIX control must be set to 100 This control can only be activated if the correct Footswitch is connected to the Footswitch DIN jack SOLO is an additional final output level control wired in parallel with the OUTPUT control It is capable of a setting above that of the OUTPUT control and can not be set below The amount of apparent boost also depends on that of the OUTPUT control in that if the amplifier is at either the extreme low or extreme high levels of the OUTPUT 69 its effectiveness is minimized It has been optimized for live performance volume levels If the power section is either not a part of the sound super quiet or producing all its rated wattage super loud there is very little signal for the SOLO control to work with By using the Footswitch and selecting HEAD VERSION PAGE 6 CONTROLS Continued SOLO Continued SOLO a pre settable boost in overall levels is possible on the fly giving you some control over your levels when it s time to step out Engineers may give you a bit of a frown the first time you use it but isn t it time you heard yourself It might even prevent them from punishing you with the dreaded monitor or sidefill ve
32. on control It is normal for high settings of this control to make Modern Red seem extremely loud in comparison to the other Modes This is a result of unclamping what worked as the Presence the other three Modes and letting the RECT O S ponies run free It is in fact the loudest setting on the amplifier Use this Presence with discretion as it can make for some ear damaging almost harsh sounds if set too high Try the Modern Mode with the GAIN control set high around to Dip the MID control then increase the Presence to dial in the right attack and blend of aggression You may want to play with the balance between the MID and PRESENCE controls as they are somewhat similar in that they are very powerful and dominant in Modern With these two controls dialed right Modern is to this day the most huge and heinous crunch we ve come across When you hear this you will probably won t believe that this could be the same amp that moments ago was crying the blues with such mournful conviction MASTER A simple control found on most amps today these serve to balance the playing level of the two channels They enable the pre amps GAIN control to be used in a wide range of settings while never having to affect the listening level On the SINGLE RECTIFIER 50 these MASTERS serve another purpose as well When the FX LOOP is in use these MASTER controls double as Effects Loop Send Level controls This is not their primary functio
33. results for tone and signal to noise ratio The EFFECTS LOOP interrupts the signal between the pre amp and power section Therefore the RETURN jack can double as a power amp input jack You will also want to run the MIX control at 100 to use the EFFECTS LOOP as a Power In patch point Connect your last effects Output jack to the Effects RETURN jack We suggest that when using the RECT O S power section only that you have the amp switched to the Rhythm channels CLEAN Mode or the Lead channels Vintage mode This assures a more neutral power sensitivity thus making the RECT O 50 more friendly to use as a power amp See PRESENCE control section of this manual for more information 10 100 FXMIX RETURN SEND REVERB RECT O VERB COMBO amp RECT O VERB HEAD These self explanatory controls deliver the rich natural reverb sound Although the circuit is the same for both RHYTHM and LEAD channels the amount of Reverb available is not In the LEAD channel there is slightly less Reverb available overall because of this channels very nature The reason behind this is two fold 1 that itis easier to prevent the massive amount of Gain and signal strength present in the Modern high gain Mode from causing unwanted Reverb oscillations 2 This channels aggressive nature lends itself more to musical styles where high settings of Reverb are simply traditional cat Don t worry there is still plenty of Reverb for
34. rsion of your tone 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 they may warm up before being put to use Before Power is switched on make sure the STANDBY switch is in the Standby position Wait at least 30 seconds and then flip the STANDBY switch to the ON position This prevents tube problems and increases their toneful life substantially ON ON POWER STANDBY HEAD VERSION This switch delivers the A C power to the RECT O 50 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 unit and that the proper voltage is present Follow the cold start procedure described in the ON STANDBY section above when powering up your new RECT O 50 ON 9 06 POWER STANDBY HEAD VERSION REST AREA 7 REAR PANEL SOLO HEAD 50 ALL TUBE AMPLIFIER VJESA JROOGLE HANDBUILTIN PETALUMA CALIFORNIA SET TO RHYTHM WHEN USING al LOOP TT RHYTHM 10 100 POWER FUSE FXMIX RETURN SEND BOHM 2000 40HM as V 25 50 60 Hz SLO PATENTED 4 211 893 AND OTHERS PENDING 25 IBLO hock REAR VIEW HEAD VERSION A C RECEPTACLE The total power consumption for the RECT O 50 is 2 5Amps 120 Volts Thus a 15 Amp circuit which is what most house circuitry is wired wit
35. stion we often hear GRID Hw PLATE Why doesn t Mesa put bias adjustments in their amplifiers Structure of a 6L 6 5881 Well there s a short answer and a long answer to this question Beam Power Pentode 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 regardless 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 h
36. t 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 yourself 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 the
37. 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 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 PAGE 20 BIAS ADJUSTMENT Continued 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 their amp altered by tubes with extreme characteristics and with the bias set to help compensate But often it is the mere
38. tless there are a few things to remember that will help you when interfacing to the RECT O for use as a power amp only 1 Connect Dummy plug or loose cable to SEND jack This prevents any possible loading that could result in diminished RETURN sensitivity 2 The OUTPUT Level will be the only active control on the Front Panel the PRESENCE control of the top Rhythm channel will be active only when that channel is engaged see 3 3 The SOLO control may be used to footswitch to a pre determined amount of boost when the footswitch is connected 4 The lower LEAD channels MODERN mode as part of its voicing utilizes substantially less negative feedback in the power stage creating a scenario of greatly increased power sensitivity This internal revoicing produces amazing results in the lead sounds and requires a sophisticated network of elements to switch to prevent the increased power sensitivity from blowing you out of the room as the LEAD channel is toggled between VINTAGE and MODERN Therefor we recommend selecting the top RHYTHM channel when you wish to use the RECT O as a power amp The more conventional power sensitivity of this channel will be the most compatible with external sources Another benefit to using the RHYTHM channel in a power only application is that the PRESENCE control will be active and allow you to tailor the power voicing to your specific tastes If you do need the extra sensitivity the MODERN mode pr
39. two distinctly different channels using either the footswitch or the Channel Select toggle switch as mentioned in the paragraph above Before discussing each control let s audition a couple of possible ways the two channels might be configured for footswitchable sounds The first example leans towards a more traditional format with a clean rhythm dialed up on the top RHYTHM Green channel and a moderate gain vintage style solo sound dialed up on the bottom LEAD Red channel CLEAN EN 0060906 ON ON 6 CN E gt 077 MASTER PRESENCE BASS TREBLE GAIN 19 Ww VINTAGE FT SW INPUT POWER STANDBY 8010 OUTPUT MODERN This second example leans in a more aggressive direction with the top channel switched to PUSHED for a crunchy high gain rhythm sound and the bottom channel switched to MODERN for a blistering lead voice INSTANT GRATIFICATION Demo Setting 2 ED e IN 979 MASTER PRESENCE BASS TREBLE GAIN J WZ VINTAGE kosa FT SW INPUT POWER STANDBY 50 SOLO OUTPUT 9 MODERN NOTE CAUTION REDUCE THE OUTPUT LEVEL CONTROL BEFORE PLAYING THESE SOUNDS AS THE ADDED GAIN INCREASES VOLUME LEVELS Now that you ve heard the SINGLE 5075 two channels let s move on to understanding the controls and their interactive roles in achieving the sounds that you want to hear PAGE 2 CHANNEL MODE SELECT Ea
40. wear faster The RECT O 50 combo only is equipped with a Celestion Custom 90 single 12 inch 8 Ohm speaker but as you can see other speaker configurations may be used When using two 8 Ohm speakers connect each of them to the 4 Ohm speaker jacks that lm 8 provided this will equal a 4 Ohm load which is the proper impedance required when using this particu lar speaker configuration 8 OHM 4 OHM 4 OHM EFFECTS LOOP SEND RETURN amp MIX These two 1 4 jacks are the patch point for external signal processing effects The EFFECTS LOOP the RECT O 50 is wired parallel with the unaffected or dry signal which enables you to preserve the integrity of the all tube tone and feel that the RECT O 50 is capable of delivering To use the EFFECTS LOOP for your processors simply connect the Effects Loop SEND jack to your first effects Input jack Connect your last effects Output jack to the Effects Loop RETURN jack EFFECTS LOOP Use the rotary MIX control to blend in the desired amount of the processed signal with the original WZ NI dry signal The least degradation of signal is usually found by setting the processor s mix at 100 and the EFFECTS LOOP MIX control at the lower end of the control In this manner the least amount of your pure tone will be processed and you will be dialing in a very small amount of a very wet signal to be mixed with the original This method seems to produce the best
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