MESA BOOGIE Owner's Manual
Hello from the Tone Farm... YOU, the smart player and all around intuitive human, have put your trust in us to be your amplifier company. This is something we do not take lightly. Our reward is that we’ve made a classic amplifier and by choosing this amplifier, you have become part of the Mesa family... Welcome! Our goal is to never let you down. Your reward is that you are now the owner of our most popular selling power amp, the 2:50. Bred of fine all tube amp heritage...
Precautions________________________________________________________________________________ 0 Overview___________________________________________________________________________________ 1 FRONT PANEL CONTROLS & FEATURES VOLUME CONTROLS: CHANNEL A / CHANNEL B_________________________________________________ 2 PRESENCE CONTROLS A & B_________________________________________________________________ 2 POWER / ON______________________________________________________________________________ 2-3 STANDBY / ON_____
PRECAUTIONS & WARNINGS Your MESA/Boogie Amplifier is a professional instrument. Please treat it with respect and operate it properly. USE COMMON SENSE AND ALWAYS OBSERVE THESE PRECAUTIONS: WARNING: EU: permission from the Supply Authority is needed before connection. WARNING: Vacuum tube amplifiers generate heat. To insure proper ventilation always make certain there is at least four inches (100mm) of space behind the rear of the amplifier cabinet. Keep away from curtains or any flammable objects.
Overview: Congratulations and Thank You for your purchase of the 2:50 Stereo Power Amplifier! Inside this clean, compact, two rack-space unit is a true guitar amp that’s unabashedly aggressive! Looking for raw punch? Guitar tone coloration? Power tube overdrive at manageable levels? You’ll find it here. The 2:50 power amplifier proves once again that killer tones can come in small packages.
FRONT PANEL CONTROLS FRONT VIEW: 2:50 CHANNEL A ON ON CHANNEL B PRESENCE A POWER STANDBY PRESENCE B VOLUME CONTROLS: Channel A & B Each channel of the 2:50 has its own VOLUME Control. If the amplifier is being fed by signals from a typical preamp, try a setting of 2 as a starting point. If the amp is being fed by lower-level signals such as those from minus 20db - type effects units, etc..., you may need to raise the Levels as high as 8.
FRONT PANEL CONTROLS (Continued) POWER ON: (Continued) Never remove any of the power cords terminals. All three terminals of the A.C. power cord must be connected and always check that the power receptacle has the proper voltage present. Also, make sure that the power cord is inserted all the way in when connecting to a power receptacle. STANDBY: Perfect for set breaks...the STANDBY switch also serves an even more important purpose.
REAR PANEL CONTROLS REAR VIEW: 2:50 WARNING: To reduce risk of fire or electric shock, replace fuse with same type and rating only. Do not expose this unit to rain, moisture or thieves. GROUND BIAS SWITCH SWITCH POWER FUSE LIFT 6L6 EL34 120 V~ 60 Hz 4A 4A SLO BLO MUST MATCH TUBES FUSE GROUND SEE OWNERS BOOK CHAN. B SPEAKERS INPUTS A FUSE INPUTS B CAUTION: To reduce risk of fire or electric shock, do not remove cover. No userserviceable parts inside. Refer all servicing to qualified personnel.
REAR PANEL CONTROLS (Continued) GROUND ISOLATION SWITCH: (Continued) NOTE: If the 2:50 is operated outside of a rack installation, the switch should generally be set to the Normal position, or else squealing, buzzing and oscillation may occur. Always check this switch before thinking that something has gone wrong with your amp! BIAS SWITCH: Your 2:50 was designed with versatility in mind.
REAR PANEL CONTROLS (Continued) TUBES: The power tubes used in the 2:50 are Mesa/Boogie STR-440 type 6L6 GC’s. These tubes have been tested in the amplifier during several “burn-in” periods before leaving the factory. You can expect 6 months to 2 years (or more) of outstanding performance from your Mesa/Boogie power tubes, depending on use. Tube wear is gradual and usually goes unnoticed until new replacements are installed. Worn power tubes tend to sound flat with reduced punch, clarity and high end.
REAR PANEL CONTROLS (Continued) A.C. RECEPTACLE: The total power consumption for the 2:50 is 4 Amps @ 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.
TUBE NOISE & 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...
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 uninterrupted performance.
BIAS ADJUSTMENT: (Part of a continuing series) CATHODE ( ) , ) GRID ( SCREEN GRID ( ) An Article written by Randall Smith that we thought you might find interesting. BEAMCONFINING ELECTRODE ( ) .. ..... .... .. ... . .... PLATE ( , ) Here’s a question we often hear: Structure of a 6L6 / 5881 Beam Power Pentode. “Why doesn’t Mesa put bias adjustments in their amplifiers?” Well, there’s a short answer and a long answer to this question.
BIAS ADJUSTMENT: (Continued) 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 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.
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 for the mis-match causes the push-pull circuit itself to become unbalanced. Two wrongs don’t really make a right. Some of the other recommended biasing, “methods” — such as -”.. tubes running red hot, increase the bias .. sounds harsh and runs too cool, turn it down ...” are guesswork at best.
SPEAKER IMPEDANCE MATCHING & 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.
SPEAKER IMPEDANCE MATCHING & HOOK-UP GUIDE: (Continued) PARALLEL: 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.
WIRING SCHEMES...
6 WIRING SCHEMES...
WIRING SCHEMES...
WIRING SCHEMES...
WIRING EXAMPLE #1 117 V~ 1 AMP 60 HZ. MESA Mesa/Boogie all tube Formula Pre-Amplifier BOOGIE CIRCUIT PATENTS PENDING LIFT GROUND FX SEND RHY - LD 100% 10% FX MIX RETURN - L LD1 - LD2 EXT SW EXT SW RETURN - R EQ LEFT REC OUT TIP RING SLEEVE RIGHT MAIN OUT HANDMADE IN CALIFORNIA SHIELDED CABLE 2:50 ALL TUBE STEREO POWER AMPLIFIER WARNING: To reduce risk of fire or electric shock, replace fuse with same type and rating only. Do not expose this unit to rain or moisture.
SUGGESTED WIRING #2 7-PIN SHIELDED CABLE MIDI FOOT-CONTROLLER TriAxis Mesa/Boogie ON/LIFT IN MIDI THRU SWITCH 1 OUT 3 RECORD OUTPUT A 4 2 RETURN B OFF ON GROUND A ll tube programmable pre-amp FX LOOP SEND INST INPUT B SHIELDED CABLE SHIELDED CABLE OUT OUT IN SHIELDED CABLES B A STEREO (MONO) MULTI EFFECTS UNIT IN MIDI OUT L OUTPUT R L INPUT R (MON0) AC POWER SHIELDED CABLE A B 2:50 WARNING: To reduce risk of fire or electric shock, replace fuse with same type and rating on
A look into the inner workings of the Vacuum Tube ON TRIODES, PENTODES & 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.
ON TRIODES, PENTODES & IRISHMEN: (Continued) Thus a diode tube - one with a cathode and an anode - is mostly used to rectify alternating current into direct current by passing it without 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.
PENTODES: (Continued) Thus the proper cocktail waitress - visible through the louvers - is scantily clad so as to be all the more effective at reinforcing the attractive influence of her bar and by being located in between the door and the bar, she serves as bait to lure customers past the door’s negative influence.
MESA BOOGIE The Spirit of Art in Technology Thank you for trusting MESA/Boogie to be your amplifier company and we wish you many years of toneful enjoyment from this handbuilt all tube instrument.
The Spirit of Art in Technology (707) 778-6565 FAX NO.
