User manual MESA BOOGIE MARK III

[. . . ] MESA-BOOGIE MARK III OPERATING INSTRUCTIONS MESA ENGINEERING CONGRATULATIONS!You've just become the proud owner of the world's finest guitar amplifier. When people come up to compliment you on your tone, you can smile knowingly . . . and hopefully you'll tell them a little about us! [. . . ] Suggested value: 8 ohms, 50 watts minimum. And note that this resistor will get quite hot when running the Boogie "up loud" for long periods. EFFECTS SEND & RETURN The Effects Loop circuitry of the Mark III is very sophisticated and works very well with nearly all units. The maximum signal strength obtainable is around 0. 6 volts RMS, or about the same as a guitar pickup. Most Marshall 4x12 cabinets are 16 ohms. By wiring all four speakers in parallel, you can reduce the cabinet impedance to 4 ohms (assuming the speakers are 16 ohms each). A MESA/Boogie 4x12 cabinet comes standard at 8 ohms. It has four 8-ohm speakers wired in series-parallel. No matter how unusual your speaker setup, it's always possible to get good performance. If you need two 8-ohm speaker jacks (in order to run two 16-ohm cabinets at the same time), you can either use a Y-box, or daisy-chain the cabinets, or even rewire the speaker lacks inside the amp so there are two 8's and one 4. (You should then re-label the rear panel to avoid confusion later. ) TUBE SWITCH This is the "Class A/Simul-Class" switch or the "60/100" watt switch, depending on amplifier type. In the Simul-Class amplifiers the power (before clip) is much less in the Class A position - mere 15 watts. But the unique way the system is wired allows you to achieve a much greater degree of power tube distortion than with most other amplifiers . . . In Class A, only the outside (outer left & outer right) pair of tubes - the EL-34's will be on. The inner pair - which are 6L6's - will also be turned on when the switch is in the Simul-Class position. In addition to this obvious difference, the biasing and control circuitry of the socket pairs are radically different . . . and this is the heart of the now famous (and patented) Simul-Class circuitry. It is worth noting that almost all of the major players who have gone over to Boogie have chosen the Simul-Class power design!NOTE: In the past, MESA/Boogie advertised the "interchangeable power tubes" feature of the Mark III Simul-Class. We told players that they could use either EL-34's or 6L6's in the outer (Class A) power sockets. However, in recent years we've observed a much greater reliability factor with the use of EL-34's in these outer sockets, with much fewer incidents of tube failure. Therefore, today we strongly recommend using EL-34's in the outer sockets and 6L6's in the inner sockets of your Simul-Class Boogie. [. . . ] This should line up with the notch in the center hole of the tube socket. Also look for the scratches in the plastic base caused by the retaining ring. When you think you've got it right, make sure the amp is on Standby, then turn on the Power. If the tube filament lights, up, then you've got it right and everything is OK. [. . . ]