The Mark III was launched by Mesa/Boogie in 1985. It introduced a third channel, a crunch rhythm sound right in between the rhythm and lead channels. This amp has a dual footswitch system: one footswitch alternates between the current rhythm mode and the lead mode, and the other selects either the clean rhythm mode or the crunch rhythm mode. The two rhythm modes share all of their controls, while the lead mode only shares the rhythm modes tone stack, featuring independent gain and master volume controls.
The physical switch for the crunch rhythm mode was implemented as a push/pull switch above the Middle frequency control. Most Mark III’s have presence and reverb on on the back (except for long chassis’) unless not desired by the buyer; Graphic EQ was also optional all in either head or combo format.
Mark III amps come in series, with each new series come new improvements ; series are called »stripes« and the five stripes were as follows:
Black Stripe (1985):
These are distinguished by either the absence of a marking, a black dot, or a black marker stripe above the power cord entry. Early Black Stripes retained the same power transformer as the IIC+, which is easily distinguished by its larger physical size than the later-introduced Mark III transformer.
Purple Stripe (1986):
The second revision was the “Purple Stripe” Mark III, which featured a purple marker stripe above the power cord. This amplifier was voiced with a more mellow lead and crunch modes, with slightly reduced gain.
Red Stripe (1987):
The third revision was the “Red Stripe” Mark III which featured a red marker stripe above the power cord. The amplifier had increased gain over the purple stripe, and lead mode circuitry almost identical to the IIC+.
Blue Stripe (1988 – mid 89):
The fourth revision was the “Blue Stripe” Mark III which featured a blue marker stripe above the power cord. The amplifier was voiced so bright, it is considered to be the most aggressive Mark Series Boogie ever introduced. The power amp was also altered to mirror that of the IIC+.
Green Stripe (1989):
The final revision was the “Green Stripe” Mark III, which was only available in a Simul-Class format. It was identical to the Blue Stripe, except for the wiring of the Class A power amp tubes, which were switched to Pentode operation instead of Triode for a 10w RMS increase over previous Simul-Class amplifiers (15w/75w) making 25w/85w. Mesa ultimately ended the Mark III’s production in the company’s largest marketing failure, since it overlapped with production of its successor, the Mark IV, which was introduced in 1990. Mark III’s were still in steady production around 1994, and finally ceased as late as 1997, 11 years after its launch.