The 400 amplifier was, perhaps, Phase Linear's most popular amplifier due
to its more than adequate 200 watts per channel and a price tag roughly
two-thirds that of the 700. The 400 was introduced in 1972 with a
list price just under $500.
Model 400 amp with output device covers
Like the 700, the 400 featured twin output meters. It had six output
transistors per channel, plus two drivers per channel, right below the
output transistors. The heatsinks were of a different design than
the 700, having less surface area. Dimensionally, it differed
slightly from the 700 only in height, measuring 19.00w x 10.00d x 7.00h.
The 400 had a factory rated frequency response of 5-250k Hz.
Phase Linear 400 Series Two
In 1978, the 400 Series Two was introduced. This model was new,
inside and out. The owners manual gave a rated output of 210 watts
per channel. More important were the improved specifications. The old-style VU meters were gone. In their place were two
multi-LED output meters, shared with the 700 and D-500 Series Two amps. Output from each channel could now be controlled by a knob beneath each
meter. Rack handles were now standard.
400 Series Two (back)
The 400 Series Two also featured redesigned
heatsinks with more surface area, like those use on the 700. When
Pioneer acquired Phase Linear in 1979, it sought to improve the specs on
the amplifiers even further. In 1980, the 400 had lower THD and
IMD of only 0.009%. The price of the 400 had risen throughout the
late 1970s, and in 1980 it listed for $700. In 1981 it rose to