The Quasi-complementary output
c200.1 is similar to the c200 except for the output stage.
Notice that all the output transistors are NPN types. This
output configuration is known as "Quasi-Complementary".
Quasi-complementary outputs came about in the early
years of solid state designs where pnp transistors were
few, costly and don't quite complement their npn counterparts.
Nowadays, with modern complementary transistors sharing
similar properties, this output topology is not often favored.
One reason is probably due to the lack of performance of
the early designs that left a bad impression. Nonetheless,
quasi-complementary outputs do have their advantages, the
most obvious being that all output transistors are identical,
unlike npn and pnp, which in reality is never truly the
The key is in Q8. Sometimes called a "complementary
phase splitter", it is actually more of a level shifter.
Together with the output transistors, they form a Sziklai
Is the Quasi-complementary inferior to the more common Emitter-follower
configuration? I don't think so, at least not in THD terms.
In amplifier stability, it is just as stable as any well
designed amplifier with EF outputs, unlike the Compound
Feedback Pairs, which can be tricky to make stable at times.
are similar to c200 (EF version), with no signs of distortion
and instability when driving 8 and 4 ohms test loads up
to rated power. Sonically, I am unable to tell the difference
between the two. In short, it is just as good and reliable
as an EF design. Actually, the thought of having all outputs
identical is a very attractive proposition.
of c200.1 quasi-complementary output
of output transistors
All THD readings were done with outputs biased to 12mV across
0.22 ohms emitter resistor. This works out to approximately
55mA per output transistor in idling state.
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