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Mesa/Boogie pmn User's Manual

1. 5 amp This is really just two sets of Series wired speakers connected Parallel This is how you maintain a consistent load with multiple speakers The importance of this is more evident when you have more than one cabinet to connect to your amplifier This is when you All 4 Spkrs are 8 Ohms need to figure out the loads and how to wire them up without applying too low of a resistance on the amplifier SPEAKER A Simply connect the Positive side of Speaker A to the Positive side of Speaker C Connect the Negative side of Speaker A to the Positive side of Speaker B Next connect the Negative side of Speaker C to the Positive side of Speaker D And lastly connect the Negative side of Speaker B to the Negative side of Speaker D SPEAKER C SPEAKER D 4 Eight 8 Ohm speakers wired in Series Parallel CY SHA Total Load of 8 Ohms i 2 XY CELESTION POSITIVE NEGATIVE PAGE 18 1 WIRING SCHEMES Amplifier to Speaker Cabinets 2 8 OHM 4 OHM 4 OHM 8 OHM 4 OHM 4 OHM 80hm Cabinet wm _ Partial back view of amplifier Partial back view of amplifier Partial back view of some Mesa amp 8 OHM 4 OHM 4 OHM e w Ne 8 Ohm Cabinet 4 Ohm Cabinet i Partial back view of amplifier Partial back view of amplifier 4 OHM 8 OHM 16 OHM 80hm Cabinet 4 OHM 8 OHM 16 OHM SAFE MISMATCH
2. YNGZ SOLO 50 0 50 Series 2 Owner s Manual Hello from tbe Farm You 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 By purchasing and choosing this unit to be a part of your musical voice 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 a great amp bred of fine all tube amp heritage benefiting from the many pioneering and patented MESA circuits that led to the refinement of your new instrument 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 5010 0 RECT 0 VERB50 Series 2 TABLE OF CONTENTS Precautions OVERVIEW INSTANT GRATIFICATION 2 DEMONSTRATION SETTINGS CHANNEL MODE SELECT CHANNEL 1 CLEAN amp PUSHED CHANNEL 2 RAW VINTAGE amp MODERN CONTROLS GAIN TREBLE MIDDLE BASS PRESENCE REVERB Rect o Verb Combo amp Heads only MASTER OUTPUT CONTROL SOLO CONTROL TOGGLE SWITCHES STANDBY POWER REAR PANEL CONTROLS SWITCHES amp JACKS SLAVE OUT SPEAKERS BIAS SELECT tA Y gt
3. This control adjusts the predominant gain stage each channels circuit with the function and taper being optimized for each individual channel Remember that your RECT O 50 is really two separate multi mode amplifiers built onto one chassis so though each channel looks identical the GAIN Control for each channel comes in a different place and adjusts a different point in that channels circuit In most guitar amplifiers and especially in all tube circuits the GAIN Control is the most powerful control in the preamp It shapes the overall style and character of the sound and is responsible for whether the sound is clean overdriven or anywhere in between In your RECT O 50 the GAIN Control is even more powerful It not only determines the amount of drive but also acts as an integral part of the tone control string as well To simplify the GAIN Controls role in shaping the overall tone of the sound we will look at it in two ways 1 alone and 2 in conjunction with the tone controls HEAD VERSION 1 By itself the GAIN Control has basically three tonal regions Low 7 00 11 00 provides the cleanest least saturated sounds and in this region the sound will be brighter and contain more upper harmonics lending a three dimensional character to the sound Middle 11 15 2 00 enhances the saturation and replaces some of the upper harmonics with a richer warmer quality and a fuller bottom end response Not yet full
4. Thus a diode tube one with a cathode and an anode is mostly used to alternating current into direct current by passing it without restriction but in one direction only This also explains why closing time is strictly enforced at Irish pubs During normal operation the traffic flow is similarly 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 layman 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 nega tive 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
5. e 6 6 10 2 OUT 4 OHM 4 8 SWITCH MUST MATCH WARNING To reduce risk of fire or electric shock replace fuse with same type and rating only Do not TO EXT PWR AMP TUBES IN USE ALL 3 JACKS pt 619112 FX MIX CONTROL pt 592736 SWITCH JACK pt 602000 pt 619112 SOLO CHANNEL FOOT SWITCH JACK pt pt 607111 610120 CLEAN POT Por POT Por 590737 590148 590378 590148 590792 PUSHED BASS MID TREBLE GAIN gw NA N POT POT POT POT PoT T INPUT 590151 590739 590737 590738 590794 E MODERN SWITCH pt 607313 NOTE CHASSIS PARTS AND THEIR RESPECTIVE NUMBERS ARE THE SAME FOR BOTH THE HEAD amp COMBO VERSIONS OF THE RECT O 50 SERIES 2 AMPLIFIERS FUSE HOLDER JACK DOMESTIC pt 790347 613600 EXPORT pt 790346 PATENTED 4 211 000 amp OTHE 15 PENDING FOR SOLO MUTE amp LOOP CONFIGURATION EXT SWITCHING 1 CHANNEL 1 POWER FUSE WARNING 120V 25A Unplug pover 50 60 Hz 510 fuse or removing 25 IBLO boats mounting switch 2 FUSE SET TO CHANNEL 1 TO USE FOOTSWITCH CAUTION To reduce risk of fire or electri shock do not remove cover user serviceable parts inside Refer AC RECEPTACLE 613713 SWITCH pt 600631 JACKS pt 619112 PAGE 31 MESA BOOGIE Ihe Spirit of Art in Tech
6. 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 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 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 bi
7. processors Input stage but will make balancing the two channels Effect Send level difficult HEAD VERSION 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 amplifier as a power amp alone by inserting a signal into the RETURN jack the OUTPUT Control will serve as the master level control HEAD VERSION NOTE When using the EFFECTS RETURN as an input to use the RECT O amplifier as a power amp the SOLO Control can be used to attain a footswitchable boost if the Footswitch is connected It is wired in 6 62 parallel to the OUTPUT Control and therefore also controls the volume of the power section er OUTPUT NOTE The Effects Loop RETURN jack can serve as a power amp input so that you may use the RECT O 50 amplifier as a power amp for either stereo reproduction or to incorporate additional pre amps Here 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
8. v DUW FX LOOP Send amp Return T n o lt amp 0 EXTERNAL SWITCHING 10 CHANNEL 5 44 1 4 4 441 FUSE 1 AC gt gt gt gt f FACTORY SAMPLE SETTINGS 123 PERSONAL SETTINGS SHEET 14 15 TUBE DESCRIPTION amp TASK CHARTS 16 SPEAKER IMPEDANCE amp POSSIBLE HOOK UP SCHEMES Amplifiers to Speaker Cabinets 17 22 DIAGNOSING POWER TUBE FAILURES amp MAINTENANCE 93 DIAGNOSING PRE AMP TUBE PROBLEMS G Q 4 BIAS ADJUSTMENT A feature article by Randall Smith 25 27 TRIODES PENTODES amp IRISHMEN A feature article by Randall Smith 28 30 PART SHEET 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 beh
9. PRESENCE OOOOOO MASTER CH1 z v lt ea z gt ms o o k gt a gt 5010 INPUT 6 27 2 2 Ini oc lt E x a gt m o eo 14 PERSONAL SETTINGS PAGE COMBO VERSION SHOWN SOLO OUTPUT CH2 CH1 MASTER PRESENCE BASS O O GAIN G E CLEAN la ND PUSHED y INPUT MODERN CH1 MASTER O O O I QO Q BASS gt z m lt u o a OUTPUT CH2 SOLO 2 lt 5 lt e A o 5010 OUTPUT CH2 CH1 O O O OOO GAIN 1 G E CLEAN 2 N PUSHED INPUT 5 MODERN CH1 MASTER 2 PRESENCE gt m lt u e N 5 o a zr ocou amp 5 PAGE 15 NOTE POWER TUBES ARE BEFORE CHANGING RECT O VERB SOLO 50 TUBE TASK CHART TUBES TURN POWER SWITCH TO OFF AND LET COOL OR USE A RAG FOR PROTECTION PARTIAL VIEW OF LARGE TRANSFORMER OF CHASSIS a HEAD VERSION Description of Tube Functions 1 Input Stage V1B 2nd Stage Rhythm amp Lead V2A 3rdStage Rhythm V2B 3rd Stage Lead V3A 4th Stage Lead V3B 5th Stage Le
10. Task Chart 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 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 bizarre noise it is considered normal and functional PAGE 24 BIAS ADJUSTMENT Part of a continuing series An Article written by Randall Smith that we thought you might find interesting GRID EA SCREEN GRID gt BEAM CONFINING ELECTRODE Here s a question we often hear Why doesn t Mesa put bias adjustments sie re in their amplifiers Structure of 616 5881 Beam Power Pentode
11. access This negative influ ence 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 similarly charged with Bias but unless you are Irish yourself this type of Biasing may be more difficult to under stand 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 easiest to overcome 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 in between widely sepa rated 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 with
12. cases you will have a number of speakers and then you must calculate the load that the ampli fier will need to support There are generally three ways to wire multiple speakers together They are as follows SERIES When you wire hook up speakers in Series the speakers resistance as measured in ohms is additive i e put ting two 8 ohm speakers in Series results in a 16 ohm load POSITIVE secu w Speaker 8 Ohms Speaker B 8 Ohms SERIES Connect the Negative side of Speaker to the Positive side of Speaker B PAGE 17 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 ohm load Connect the Positive side of Speaker A to 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 CELESTION NEGATIVE POSITIVE Total Load 4 Ohms
13. e CH2 CLEAN INPUT moraz lt CLEAN INPUT MODERN CLEAN 63 e MASTER PRESENCE BASS MID TREBLE GAIN idm RAW sio 9 e e CH2 MODERN CLEAN e 62 e MASTER PRESENCE BASS MID TREBLE GAIN s n RAW sio e 2 INPUT 2 MODERN PAGE 12 FACTORY SAMPLE SETTINGS COMBO VERSION SHOWN Sparkling Clean CLEAN IN pi GAIN TREBLE MID BASS PRESENCE RAW INPUT WT E MODERN CLEAN e o9 la GAIN TREBLE MID BASS PRESENCE 4 e e e e INPUT 2 MODERN Blues Lead Both Channels GAIN TREBLE MID BASS PRESENCE 1 6 MODERN CLEAN High Gain Lead Crunch Both Channels CLEAN 1 PUSHED GAIN TREBLE MID BASS PRESENCE RAW INPUT mo aAz MODERN PAGE 13 MASTER MASTER MASTER MASTER OUTPUT OUTPUT OUTPUT OUTPUT PERSONAL SETTINGS PAGE HEAD VERSION SHOWN SOUND 1 a z z tc lt lt gt mc a z TREBLE GAIN MID PRESENCE MASTER CH1 e0 O O O O O SOLO OUTPUT INPUT CLEAN PUSHED 1 RAW o 8 MODERN GAIN O TREBLE
14. group of frequencies that tend to soften or stiffen the way a sound feels to play Most players tend to lean in the direction of lower MIDDLE Control settings 7 00 11 00 where scoop this region produces girth by letting the Bass become a little more dominant and a lack of punch lends e more compressed even feel to the strings and therefore less apparent resistance to the pick As the MIDDLE Control is increased 11 30 1 30 the sound is rounded out and filled in with a focused mid attack appear MID TREBLE ing rather quickly As you would guess the feel starts to change becoming more resistant Above this region the MIDDLE Control could be used to compensate for either weaker pick ups or for times when a specific deficiency is produced by either an extremely high setting of other tone controls or a physical anomaly the room While these MIDDLE Control settings 2 00 5 00 can introduce added gain and create enhanced HEAD VERSION focus the trade off will be a stiffer more forward less compressed feel Channel 1 utilizes a different MIDDLE Control than that of the Channel 2 with a custom designed taper and value In its low range below 12 00 it functions as a normal midrange control with a taper suited to blending fine increments of these frequencies Most players lean toward a fairly radical scoop 7 00 10 30 for clean playing preferring to let Treble and Bass remain dominant thus producing
15. happily send you a replacement Just note the color designation on the tube label so that we can send you the appropriate match PAGE 23 DIAGNOSING PRE AMP TUBE PROBLEMS 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 unin terrupted 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 instru ments volume off or unplugged altogether unlike pick up feedback which ceases as the instrument is turned down Microphonic 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 channe
16. jack combinations have 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 PANEL HEAD VERSION SOLO 50 HEAD SERIES 2 Instant Gratification Demo Settings CLEAN PUSHED MASTER PRESENCE BASS TREBLE GAIN WZ RAW INPUT POWER STANDBY 5010 9 6 9 9 MODERN REAR PANEL HEAD VERSION SOLO 50 HEAD SERIES 2 SINGLE RECTIFIER SERIES 2 SOLO HEAD ALL TUBE AMPLIFIER HANDMADE IN PETALUMA CALIF USA MESA BOOGIE r FX LOOP 1 EXT SWITCHING E54 D0OGIE 1 SLAVE SPEAKERS BIAS SWITCH FX MIX RETURN SEND SOLO CHANNEL gt gt POWER FUSE 7 N 7 V N 2 Y 7 N 7 N N Y NO 253 86 EL34 Y Y Y 50 60 Hz 510 m 1 90 25 BLO Sols mounting re or electi PATENTED 4 211 000 8 OTHERS PENDING FOR SOLO MUTE amp LOOP CONFIGURATION CHANNEL 1 OUT 40HM 40HM 80HM GUON switch 2 FUSE WARNING To reduce risk of fire or To TO EXT PWR AMP SWITCH MUST MATCH secti shock replace fuse wih o SET TO CHANNEL 1 TUBES IN USE cn Hot CET news TO USE FOOTSWITCH FRONT PANEL COMBO VERSION RECT O VERB 50 SERIES 2 4 amp 6 9 e e 2 PUSHED WZ GAIN T
17. least degradation of signal is usually found by setting the processor s mix at 10096 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 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 90 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 50 s power section only that you have the amp switched to Channel 1 s CLEAN mode or Channel 25 MODERN 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 MEUM These jacks allow usually MIDI programmed operation of your amplifier s functions from an external switching source The switching is accomplished by connecting shorting the jack s Tip to its Ring or ground r EXT SWITCHING 1 5010 CHANNEL 7 N N Y CAUTION To reduce risk of fire or electric o not remove cover No user 0 inside Refer ied personnel shook d serviceable servici
18. p MESA i 16 Ohm Cabinet 16 Ohm Cabinet SAFE MISMATCH PAGE 19 6 WIRING SCHEMES Amplifier to Speaker Cabinets 7 Partial back view of amplifier Partial back view of amplifier 8 OHM 4 OHM 4 OHM 4 OHM 4 OHM 8 OHM 8 Ohm Cabinet 8 Ohm Cabinet 8 Ohm Cabinet 16 Ohm Cabinet CORRECT MATCH SAFE MISMATCH Partial back view of amplifier Partial back view of amplifier 6 8 OHM 4 OHM 4 OHM 4 OHM 4 T 9 CORRECT MATCH CORRECT MATCH 4 Cabinet 4 Cabinet 16 Ohm Cabinet 16 Ohm Cabinet PAGE 20 WIRING SCHEMES Amplifier to Speaker Cabinets Partial back view of amplifier 4 OHM 4 OHM 8 OHM 16 Ohm 67 8 Ohm 8 Ohm 80hm Cabinet 80hm Cabinet 80hm Cabinet SAFE MISMATCH 9 Partial back view of amp pe ires 1 CORRECT MATCH BOHM 4OHM 0 5 _ AL 16 Ohm Cabinet 16 Ohm Cabinet SAFE MISMATCH 16 Ohm Cabinet 16 Ohm Cabinet PAGE 21 WIRING SCHEMES Amplifier to Speaker Cabinets Partial back view of amplifier 16 Ohm 4OHM 40HM 8 OHI SERIES BOX 80hm Cabinet 80hm Cabinet 16 Ohm Cabinet SAFE MISMATCH Partial back view of amplifier 8 OHM 4 OHM T 16 Cabinet 16 Ohm Cabinet 16 Ohm Cabinet SAFE MISMATCH PAGE 22 TUBE NOISE amp MICROPHONICS may occasionally experience some form of tube noise or microphonics Certainly no cause for alarm this quirky behavior comes wi
19. 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 remove the chassis from the cabinet by unscrewing the four mounting bolts on the bottom top The chassis then slides back like a drawer and comes out from the back 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 Remove the Rectifier tubes and wrap them also You can leave the preamp tubes in or remove them and wrap them separately being sure to label their location See Tube
20. the 871 modes and is optimized for producing balanced IN pristine clean sounds For the best understanding of how to achieve a great sound in this mode please refer PUSHED back to the GAIN Control section of this manual However a great place to start is 12 30 or so on the GAIN INPUT Control with more sparkle available below this and more warmth apparent above from there adjust according to your guitars individual response Because of its more traditional architecture this mode also works extremely well for vintage style drive sounds By turning the gain all the way up a beautiful old school solo sound is possible especially with neck single coil pick ups The TREBLE and MIDDLE Controls can also add gain and sustain to this sound reduce Presence to blend highs but you will probably want to run the BASS Control below 10 30 to avoid flubbiness and preserve a focused attack PUSHED This mode is a radical departure from the sweet shimmering blend of the CLEAN modes low gain character Huge increases in gain early on in the first stages of the pre amp produce one of the biggest differences between modes in the entire amplifier and transforms what you thought to be a tame and gentle clean channel into a raging crunch machine This incredible amount of gain also creates one of the most expressive solo modes in your RECT O Because there are less stages of gain for the signal to travel through and the tone control network is tune
21. the two channels via the manual Channel Select toggle switch located on the Rear Panel 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 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 CHANNEL 1 Green and a moderate gain vintage style solo sound dialed up on CHANNEL 2 Red This second example leans in a more aggressive direction with CHANNEL 1 switched to PUSHED for a crunchy high gain rhythm sound and CHANNEL 2 switched to MODERN for a blistering lead voice NOTE CAUTION REDUCE THE OUTPUT LEVEL CONTROL BEFORE PLAYING THESE SOUNDS AS THE ADDED GAIN IN CREASES VOLUME LEVELS Now that you ve heard t
22. 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 mo ments 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 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 Disi Often caused by contamination within in a
23. 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 12 7 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 Road King on Standby remove it from its socket and turn it back on It will cause no damage to run the Road King 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 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
24. 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 SLAVE loud high pitched squeal will occur OUT 4 OHM TO EXT PWR AMP SPEAKERS 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 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 SINGLE RECTIFIER SERIES 2 SOLO HEAD configurations may be used ALL TUBE AMPLIFIER HANDMADE IN PETALUMA CALIF USA SLAVE p SPEAKERS When using two 8 Ohm speakers connect each of them to the 4 Ohm speaker jacks that are provided this will equal a 4 Ohm load which is the proper impedance required when using WOW N particular speaker configuration OUT 4 4 8 TO EXT PWR HEAD VERSION Your RECT O 50 amplifier was designed with versatility in mind So to add to the already awesome array of on board features we felt it essential that these new RECT O 50 Series 2 amplifiers be able to adapt their power output section 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 sou
25. REBLE MID BASS PRESENCE REVERB MASTER RAW 4 5010 Y STANDBY POWER MODERN ep REAR PANEL COMBO VERSION RECT O VERB 50 SERIES 2 PATENTED 4 211 000 amp OTHERS PENDING FOR SOLO MUTE amp LOOP CONFIGURATION SINGLE RECTIFIER SERIES 2 RECTOVERB EXTERNAL SWITCHING 1 PARALLEL EFFECTS LOOP 1 5 Boos ALL TUBE AMPLIFIER HANDMADE IN PETALUMA CALIF USA CHANNEL SOLO REVERB SEND RETURN FX MIX CHANNEL 1 SLAVE SPEAKERS WARNING POWER FUSE BIAS SWITCH 1 n 120V 25 gt 50 60 Hz 510 T Bots mount d 25A 8 0 10 90 FUSE CHANNEL 2 FOOTSWITCH SOCKET CAUTION SET TO CHANNEL 1 adm ino remove cover No 2 a SWITCH MUST MATCH 8 OHM 40M OHM OUT TO USE FOOTSWITCH ng ce Do mot mmm serment parts nie Rar TUBES IN USE COMBO USEWITHTWOBOHMSPKRS TO EXT PWR 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 VERB Series 2 amplifiers use a DIN jack located on the underside of the chassis s outer edge Labeling which reads FOOTSWITCH SOCKET BELOW should help you locate the jack SOLO 50 HEAD Series 2 amplifiers have their DIN Jack located on the Rear Panel proper See illustration at the bottom of this page If the footswitch is not available you may select
26. ad V4A FX Send V4B FX Return V5 A V5 B gt Phase Inverter PAGE 16 SPEAKER IMPEDANCE MATCHING amp HOOK UP GUIDE IMPEDANCE Wiring up speakers 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 5 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 WHAT IS MY CABINETS IMPEDANCE you have only a single speaker you just match that single speakers impedance to the amplifier and you are done In many
27. aming in rage and frustration Once heated the intrinsically negative electrons are energetic little fellows of almost no mass Thus they may be accelerated al most 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 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 stand ing in the way full uninhibited flow to the plate occurs sort of like removing the doors a
28. as 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 don t draw 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 t
29. asier to prevent the massive amount of Gain and signal strength present in either of Channel 25 high gain modes from causing unwanted REVERB oscillations e 2 This channels aggressive nature lends itself more to musical styles where high settings of REVERB are simply not traditional Don t worry there is still plenty of REVERB for drenched solo ENCE REVERB MAST work in both the RAW amp MODERN Mode in Channel 2 Simply run the REVERB Control a little E 9 6 higher than that of Channel 1 PAGE 6 CONTROLS Continued This control is the master feed from the end of the pre amp to the driver stage and the Effects Loop As you can see each Channel is fitted with its own MASTER Control enabling the two channels relative volumes to be matched regardless of their extremely different sound styles and gain signatures The MASTER Control makes possible a wide range of sounds through its ability to use very low Gain sounds at high volumes and conversely high Gain sounds at low volumes and everywhere between C e Again we suggest using the MASTER Control in its sensible ranges 9 00 2 00 Here the channels will MASTER PRESENCE be easier to match with each other and the Effects Loop will see more reasonable signal levels NOTE Because the MASTER Control creates the send to the Effects Loop extreme settings will cause a large signal to be sent to the Loop for that Channel Not only may this cause possible overloading of the
30. atively 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 over come 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 of 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 30 FRONT VIEW HEAD VERSION BOTH SWITCHES LIGHT RECEPTACLE pt 600631 pt 703850 CH1 ON ON POT A pe O 590738 e OL Pot Ri 590148 590148 MASTER STANDBY SOLO 50 SOLO CH2 RED LENS Gut BULB pt 703782 pt 703047 15 138 Located on the Front Panel 1 REVERB 2 CONTROLS 590151 RECT O VERB ALL CONTROL KNOBS ONLY Pt 408110 JACKS pt 619112 REAR PANEL HEAD VERSION SINGLE RECTIFIER SERIES 2 SOLO HEAD ALL TUBE AMPLIFIER HANDMADE IN PETALUMA CALIF USA MESA BOOGIE Fx Loop J SLAVE p SPEAKERS BIAS SWITCH FX MIX RETURN SEND N N 2 N 2
31. bes in the shotgun troubleshooting tradition and save the replaced set as spares Spare fuses are a must for the fabled cord HEAD Pag along with your spare tubes Always carry both for they could be worth their weight in gold someday 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 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 POWER FUSE oe wave 25A 50 60 Hz 510 bolts mounting 25A BLO chassis CE necessary from time to time for noise problems HEAD VERSION 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 PAGE 11 FACTORY SAMPLE HEAD VERSION SHOWN YIN Sparkling Clean e e e e PUSHED e MASTER PRESENCE BASS MID TREBLE GAIN m CH2 Pushed Bluesy Rhythm Solo Both Channels e e e e e 6 PUSHED 6 MASTER PRESENCE BASS MID TREBLE GAIN 24 5010 OUTPUT e e
32. d for the brighter nature of clean sounds this mode responds quicker to your pick attack and has more urgent snappy feel Don t overlook this mode for some of the RECT OS coolest overdrive solo sounds NOTE When using PUSHED with the GAIN Control maxed 5 30 do not run the TREBLE Control above 2 30 Settings above 2 30 can create possible oscillation in certain preamp tubes in the V 1 position This can be avoided altogether by setting the TREBLE Control sensibly when the GAIN Control is maxed Use the PRESENCE Control for additional brightness CHANNEL 2 Modes RAW This new RECT O mode has the lowest gain of the three in the high gain lead channel Its less saturated nature greatly en hances the already versatile bevy of sounds the lead channel offers The range of gain available covers an extremely wide spectrum and it can be set to double as a formidable alternate clean mode a low gain purring blues sound and beyond all the way up to a grinding crunch or searing solo sound MAN RAW The TREBLE can be set relatively high 2 00 to add a little more gain shred when using RAW for certain N INPUT crunch rhythm sounds Don t overlook the amazing low and medium gain soloing potential RAW offers as 5 its more gradual GAIN response produces a wide range of voice like single note sounds that somewhat MODERN more dynamic due to less saturation HEAD VERSION VINTAGE This high gain mode is the famous liqu
33. e 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 Guar anteed 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 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 fac tory and which have the possibility of being outside the performance window we select for your amp And it pains us to hear the h
34. ere is an optimum region of the TREBLE Control where ample top end is mixed in and yet enough signal is still passed on to the MIDDLE and BASS Controls e E Between 11 00 and 1 30 is where you ll find the sweet spot There are definitely great sounds above and Mel below this middle region but the balance between the TREBLE Control and the other two tone controls is compromised 6 The one place you may want to throw caution to the wind and set the TREBLE Control above this median _ zone presents itself in Channel 1 of your new RECT O 50 both modes Clean amp Pushed the TREBLE HEAD VERSION Control can be used to dump extra gain into the mix This is especially effective in the PUSHED mode for crunch sounds When doing so use the PRESENCE Control to roll off some of the more than ample top end for a more compressed feel and fatter voice As you might surmise the BASS Controls effectiveness will be reduced so you may have to run a much higher setting than you are used to seeing to achieve a balance This said keep in mind that the TREBLE Control in Channel 1 Pushed should not be set much above 2 30 to avoid unwanted microphonic tube problems MID The MID Control is responsible for the blend of midrange frequencies in the mix and though its effect is not as dramatic as that of the TREBLE Control it plays an integral part in achieving any sound in your RECT O 50 It is capable of changing the feel dramatically as it blends in a
35. es and controls Do not use solvents such as benzene or paint thinner to clean the unit Wipe off the exterior with soft cloth YOUR AMPLIFIER IS LOUD EXPOSURE TO HIGH SOUND VOLUMES MAY CAUSE PERMANENT HEARING DAMAGE No user serviceable parts inside Refer service to qualified personnel Always unplug AC power before removing chassis EXPORT MODELS Always insure that unit is wired for proper voltage Make certain grounding conforms with local standards READ AND FOLLOW INSTRUCTIONS OF PROPER USAGE SOLO 20 0 0 Series 2 Operating Instructions Congratulations on your choice of the SINGLE RECTIFIER 50 Series 2 amplifier You have purchased a 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 Series 2 standing alone instantly a classic destined for vintage status With two channels housing five 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
36. 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 504 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 12 7 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 numbered 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 scre
37. g all the way up If you are not able to achieve the sound you want at sensible settings on any or all of the controls your problem may lie elsewhere in the signal chain i e pick ups cabinetry processing etc Keep in mind you can always call on one of our product specialist Monday through Thursday and seek some advice should you find yourself struggling to get the sound you want PAGE 4 CONTROLS Continued 2 GAIN In conjunction with the Tone Controls Basically a simple rule applies as the Gain is increased the Tone control string has less and less effect on the signal until at 5 00 the signal is so saturated that you are getting mostly Gain and very little Tone Again this is the reason we suggest using the GAIN Control in its middle region Here the Tone control string is very active and provides maximum shaping power allowing you to dial virtually any sound you desire As in most tube guitar amplifiers the TREBLE Control in both channels of your RECT O 50 is the most powerful of the rotary controls and is next in line only to the GAIN Control as a shaping tool Because it is first in the signal path of the tone controls and from here the Middle and Bass receive their signal it is by far the dominant tone control For this reason the setting of the TREBLE Control is very important for equal representation of the three frequency regions to appear at their respective controls Like most of the controls on your RECT O 50 th
38. he RECT O 50 s two channels let s move on to understanding the controls and their interactive roles in achieving the sounds that you want to hear INSTANT GRATIFICATION Demo Setting 1 SEN ON ON SEN AF V PUSHED PRESENCE TREBLE mw T POWER STANDBY of 67 e PRESENCE POWER STANDBY 50 soto OUTPUT e CH2 RECT O VERB COMBO Series 2 SOLO 50 HEAD Series 2 PATENTED 4 211 000 amp OTHERS PENDING FOR SOLO MUTE amp LOOP CONFIGURATION PATENTED 4 211 000 amp OTHERS PENDING FOR SOLO MUTE amp LOOP CONFIGURATION CHANNEL 1 FOOT CHANNEL 1 WARNING POWER FUSE be cs 120V 25 POWER FUSE WARNING erremoving 50 60 Hz 510 120V 25A She Hiz BLO FOOTSWITCH si sto 2 FUSE CHANNEL 2 SOCKET CHANNEL2 254 810 E imu BELOW SWITCH FUSE SET TO CHANNEL 1 SET TO CHANNEL 1 TO USE FOOTSWITCH TO USE FOOTSWITCH PAGE 2 CHANNEL MODE SELECT Each channel of your amplifier contains 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 HEAD VERSION 1 CLEAN This is the lowest gain circuit of
39. id RECT O voice and it can be found in its original state here in CHANNEL 2 Its lush harmonic content and fat creamy feel has found its way onto so many recordings it is now a staple for anyone headed to the studio for an album project Combining this super juicy expressive preamp with the RECT OS magic 50 watt power section creates colors in gain that most players find truly addictive Single note solo work is effortless as the strings become easy to play with VINTAGE modes musical and natural tube compression Spend time learning the lower regions of the VINTAGE mode as the overlap between RAW and VINTAGE is a place where many beautiful sounds lie These two modes are similar enough when VINTAGE is set in its lower range and RAW is set in its medium to higher range and yet each possesses a character that is unique and identifiable You will likely find your new trademark lead sound lurking somewhere in this sea of liquid gain PAGE 3 CHANNEL MODE SELECT Continued MODERN Aggressive This is the word that best describes the menacing power of the RECT OS most rebellious of all modes A take no prisoners crushing assault of top end cut and lightning fast response creates a sound of unparalleled aggression that has set a new standard for hard core sounds The added tightness of the low end response combined with the radically more present top end keeps the MODERN mode tracking accurately even at extreme gain settings Egg
40. in 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 PENTODES 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 attraction 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 be tween windings of
41. ind 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 use only same type and rating Avoid direct contact with heated tubes Keep amplifier away from children Be sure to connect to an AC power supply that meets the power supply specifications listed on the rear ofthe 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 switch
42. ing that the same current flows through each one PAGE 26 BIAS ADJUSTMENT Continued Again this has some merit but it s still not as good as using tubes that are matched in the first place because compensating forthe 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 their amp altered by tubes with extreme characteristics and with the bias set to help compen sate 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 th
43. l 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 performance 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 Occasion ally an anemic driver tube will cause the amplifier to sound flat and lifeless but this is somewhat uncommon 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 ATIME 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
44. ly equal representation of all the frequen e cies on the tone controls and provides a great neutral starting point for further tweaking BASS MID HEAD VERSION The PRESENCE Control is a high frequency attentuator that is placed at the end of each channels pre amp stage and affects frequencies higher than those of the TREBLE Control It acts independently of the other rotary tone controls and is crucial in voicing the Channel It is a powerful global tone control Lower PRESENCE Control settings darken and in fact compress the signal which works well to fatten single note solo sounds giving them girth and focus Some of the best lead sounds in your RECT O will find the PRESENCE Control in its lower regions where a balanced vocal response is achieved Higher settings unleash the mighty roar of your RECT O and this can be great for sparkling clean sounds e in Channel 1 and more aggressive crunch rhythm sounds in the high gain modes Be sure to taunt the beast that lurks in Channel 2 MODERN as the PRESENCE is truly amazing in this most agro mode PRESENCE BASS HEAD VERSION REVERB RECT O VERB COMBO amp HEAD These self explanatory controls deliver the rich natural reverb sound Although the circuit is the same for both Channel 1 amp Channel 2 the amount of REVERB available is not In Channel 2 there is slightly less REVERB available overall because of this channels very nature The reason behind this is two fold 1 that it is e
45. nd 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 cham pagne 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 beverage 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 28
46. nding amps created in Great Britain MESA BOOGIE and used on some of the best recordings to date BIAS SWITCH di 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 sound know that nothing has the lushness of harmonics or Wire MOT MATCH spread like a power amp using EL34 s In truth EL34 s do focus in on a region of upper harmonics that 6165 reproduce but not really enhance the same way the EL34 s do This characteristic is sometimes preferred for sounds that range from a soft clip that would be used for PAGE 9 REAR PANEL Continued chording or soloing to an all 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 new RECT O 50 amplifiers If you need a variety of sounds and rely ona clean chording sound much of the time you will likely prefer the stock compliment of 6L6 s that both of these two versions are 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 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 tha
47. ng to qualifi PAGE 10 REAR PANEL continued 21532398 This switch simply allows you to switch between the two channels CHANNEL 1 and CHANNEL 2 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 position CHANNEL 1 CY 0 CHANNEL 2 SET TO CHANNEL 1 TO USE FOOTSWITCH This is the 5 Alternating Current main fuse and provides protection from outside 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 PATENTED 4 211 000 amp OTHERS PENDING FOR SOLO MUTE amp LOOP CONFIGURATION POWER FUSE 120V 25 50 60 Hz SLO 25A IBLO FUSE 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 tu
48. nology 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 a The Spirit of Art in Technology 1317 Ross Street Petaluma CA 94954 USA Phone 707 778 6565 Fax 707 765 1503 09 18 06
49. rimmer 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 PAGE 25 control grids Voltage and current 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 carpeted 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 cur rent 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 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 p
50. roduce 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 fluctuations in that current flow when you ARE playing If the amount of current increases and decreases 440 times per second then you ll hear an A note If the fluctuations 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 because the circuit must be interrupted 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 PAR ALLEL 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 importan
51. s and increases their toneful life substantially 0 STANDBY HEAD VERSION POWER This switch delivers the A C power to the 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 50 POWER STANDBY HEAD VERSION PAGE 8 REAR PANEL SINGLE RECTIFIER SERIES 2 SOLO HEAD ALL TUBE AMPLIFIER HANDMADE IN PETALUMA CALIF USA MESA BOOGIE EXT SWITCHING 4 SLAVE SPEAKERS BIAS SWITCH FX MIX RETURN SEND SOLO CHANNEL Foor PATENTED 4 211 000 amp OTHERS PENDING FOR SOLO MUTE amp LOOP CONFIGURATION CHANNEL 1 AEN POWER FUSE peus 120V 25 6L6 Lm EL34 ii e 40 4 HM 8 switcH CHANNEL 2 FUSE OUT TO EXT PWR MUST MATCH oret TO CHANNEL 1 UBES IN USE expose this ur servicing TO USE FOOTSWITCH REAR VIEW HEAD VERSION This 1 4 jack provides a signal derived from the speaker jack Perfect for using 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 SINGLE RECTIFIER SERIES 2 ALL TUBE AMPLIFIER HANDMADE IN PETA
52. t 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 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 amplifiers 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 insur
53. t they do not appear to be as rugged in construction as the available 6L6 This is another reason why your new RECT O 50 amplifier 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 Make sure that the BIAS Switch is set correctly to match the tube type that you are using Failure to do this will result in tube failure that could possibly burn resistors in the Bias supply Although this is a fairly simple repair for an authorized technician it is easily avoidable ALWAYS CHECK THE BIAS SWITCH setting if you experiment with alternate tube types and you will enjoy uninterrupted performances from your amplifier PUE These two 1 4 jacks are the patch point for external signal processing effects The EFFECTS LOOP the RECT O 5015 wired in parallel with the unaffected or dry signal which enables you to preserve the integrity of the all tube tone and feel that the 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 5 94 jack Connect your last effects Output jack to the Effects Loop RETURN jack FX MIX RETURN SEND 9o Use the rotary MIX Control to blend in the desired amount of the processed signal with the original wn F dry signal The
54. th 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 com mon 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 check es 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
55. 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 stopping them 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 PAGE 29 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 doors 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 hav ing happily reached their destination If you re still following this and haven t lost track of the count you ll know still one element short of the five needed to make a Pentode This last part is a pair of beam confining shields which being neg
56. the only active control on the Front Panel the PRESENCE Control of Channel 1 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 Channel 2 s 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 Channel 2 s RAW amp MODERN modes are toggled between Therefor we recommend selecting Channel 1 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 Also using Channel 1 in a power only application means that the PRESENCE Control will be active which allows you to tailor the power voicing to your specific tastes If you do need the extra sensitivity that Channel 2 s MODERN mode produces for a source that is unusually weak it is there if you need it 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 90 PAGE 7 CONTROLS Continued This control can only be activated if the correct Foots
57. the signature sparkle and breath essential for a pristine clean sound PAGE 5 CONTROLS Continued As Channel 15 MIDDLE Control is swept past 1 00 it quickly starts to add gain in these midrange frequencies adding cut and punch As the top end of the control is reached 3 00 5 00 it becomes an additional gain control capable of taking both CLEAN and PUSHED modes to extremes Experiment with this cranked region in conjunction with conservative settings of the other tone controls to balance both sound and feel While this added flexibility may make Channel 1 s MIDDLE Control a little more tricky to learn at first it will become quite valuable as you start to realize the power of this super versatile channel Last but not least in the string of tone controls we come to the BASS This control works similarly in both channels in that it determines the amount of low frequencies present in a sound However the actual frequencies and style of lows it mixes in changes from channel to channel Like the MIDDLE Control it falls in line signal wise afterthe TREBLE Control and the same scheme applies _ _ When the TREBLE Control is set high the effectiveness of the BASS and MIDDLE Controls is reduced If e e the TREBLE Control is set low these two controls become dominant For the most balanced sound and a balance of power between the three rotary tone controls try to use the TREBLE Control in its middle ranges This scenario produces near
58. witch 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 HEAD VERSION is at either the extreme low or extreme high levels of the OUTPUT its effectiveness is minimized It has been optimized for live performance volume levels e e 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 forthe SOLO control to work with By using the Footswitch and selecting SOLO SOLO OUTPUT apre settable boost 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 version of your tone MP 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 problem
59. y saturated this region is the easiest place to get a great sound in all three channels This region contains many of the RECT OS best sounds especially for soloing due to the crucial blend of an expressive attack combined with ample sustain High 2 15 5 00 saturates the signal and enhances low and low mid frequencies While this region provides the maximum satu ration and therefor sustain it also compresses and softens the attack characteristics For this reason we suggest using this higher region of the GAIN Control sparingly and only when maximum sustain is needed NOTE Due to the RECT OS extreme gain potential the highest regions of the GAIN Control may possibly push the pre amp tubes past what they can handle producing microphonic squealing While we screen and test the tubes your amplifier was shipped with and the tubes in your amp passed our rigourous test we can t predict how the tubes will respond over time exposed to extreme gain settings Your tubes are warranted for a period of 6 months under normal use but you can save yourself the present and future inconvenience of having to deal with annoying microphonic tube problems by simply using a little common sense Don t turn the Gain all the way up If you must for a specific part or at very low volumes back down the TREBLE and PRESENCE Controls Your RECT O 50 was designed to provide amazing gain and tone at less than extreme settings removing the need for you to crank everythin
60. ype 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 PAGE 27 ONTRIODES PENTODES amp IRISHMEN 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 in the count Its purpose is to excite elec trons from the cathode coating by raising the temperature such that they are able to boil out of the electron rich coating material and

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