1.5 Ace-Bass Circuits
The Power Amplifier together with Z401 (1, 2, 3) and Z401 (12,
13, 14) form the Ace-Bass amplifier, which can be represented
by the diagram below.
R418 and Z401 (12, 13, 14) sense the current through the drivers.
The voltage in test point (J) equals the driver current (1V/1A).
Z401 (2, 3, 1) works as an active bandpass filter, and also sums the
signals in test points (E) and (J).
The Power Amplifier is of inverting type , and also acts as
a summing amplifier, adding signals (F) and (J).
Part of the driver current signal is fed back positively through
the Power Amplifier, which gives the Power Amplifier a negative
output resistance Rs. The amount of positive feedback, and thereby,
the value of Rs, can be adjusted by trimpot Rrs.
The parallel circuit Lp, Rp, Cp in the Ace-Bass amplifier is
accomplished through negative feedback of the driver current
signal via the bandpass filter, (Z401 (2, 3, 1) ).
