Recently acquired this Mission Power Amplifier.
In 1982 the Mission 776-777 pre/power amplifier combination replaced the original 771/772 system. The 777 broke with Mission tradition by using paralleled complementary FET output devices instead of the usual bipolar transistors. This amplifier was well regarded for its sound; less so for its rather brutal looks and whilst innovative in many ways it had the great limitation that it didn't work well with pre-amplifiers other than the Mission 776. The reason for this was the fact that the 777 was a shunt feedback dc coupled design so there were no capacitors in the direct signal path. This mean't that there could be the problem of a dc 'offset' voltage appearing across the loudspeakers. This dc voltage was minimised by careful selection of several resistors in the factory but the setting assumed that the output resistance of the pre-amplifier would be that of the 776 design. Install a different pre-amp. and you could have unacceptable voltages across the loudspeakers.
The 777 was revised in 1983 as the 777BU model and largely discontinued in 1984 when the smaller Cyrus 778 amplifier was launched. It was a double mono unit with two amplifiers and two power supplies in the one case following the format of the earlier 772. The transformers were big 300VA "EI" types (not toroids) and the reservoir capacitors were ELNA Hi-Grade Lytics, 8x 15.000µF/63V, The output MOSFETs were Hitachi 2SJ50/2SK135s (alternatively 2SJ55/2SK175 or 2SJ56/2S176).
The output was rated at 100 wpc into 8 ohms and about 250 watts into 2 ohms was achieved on a good day. The frequency response was DC-400 kHz +0/-3dB. It retailed for £750.00 which was considered to be expensive at the time.
Text courtesy of Stan Curtis.
