The Unofficial History of the Mesa/Boogie Mark Series

If you have a simul-class amp, running all four tubes generates approximately 75 watts RMS of power, while running only the class A tubes produces about 15 watts. You could also get a non-simul-class Mark IIB in a 100 watt model, which allowed to shift down to 60 watts by turning off a pair of power tubes. ................
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