n Power ampliﬁ er assemblyPower ampliﬁ er assembly with
three parallel push-pull power MOS-FET
pairs per channel mounted directly to large heat
sink, MCS+ circuitry, and current feedback ampliﬁ er.
Current feedback principle assures excellent
phase characteristics in high range
As shown in the illustration, the A-35 uses the
output signal current rather than voltage for
feedback. Since the impedance at the current
feedback point is very low, there is almost no phase
shift. A minimal amount of NFB therefore results in
maximum improvement of circuit parameters.
Trans-impedance ampliﬁ er Amp-
Principle of current feedback ampliﬁ er
Instrumentation amp conﬁ guration allows
fully balanced signal paths
The newly adopted “instrumentation ampliﬁ er”
principle ensures that all signal paths from the
inputs to the power amp stage are fully balanced.
This results in excellent CMRR (common mode
rejection ratio) and minimal distortion. Another
signiﬁ cant advantage is the fact that external noise
and other external inﬂ uences are virtually shut
out. The result is a power ampliﬁ er with drastically
improved operation stability and reliability.
Further refined MCS+ topology reduces
noise even further
Accuphase’s original MCS (Multiple Circuit
Summing) principle uses a number of identical
circuits connected in parallel to achieve superior
performance characteristics. MCS+ is a further
reﬁ ned version of this approach. By extending
parallel operation to the class A drive stage of
the current/voltage converter, the noise ﬂ oor has
been further lowered.
Signal input stage Power ampliﬁ er stage
Instrumentation ampliﬁ er conﬁ guration
Instrumentation ampliﬁ er and
further reﬁ ned MCS+ topology