Adcom GFA-575se, User Manual

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without repetitive destruction of the loudspeaker load.
To achieve the above, 12 pairs of specially selected TO-3-type, metal-cased bipolar output
transistors are used in the GFA-575se in a triple-Darlington configuration of its driver and
output stages. The safe operating area of these transistors, along with their circuit topology,
insures very efficient power delivery to reactive loads, regardless of the phase angle of
voltage and current. Many protections & current-limiting circuitry is used in the GFA-575se
which could grade the safety.
The power supply in the GFA-575se has enormous reserve power capability with an
extremely large transformer feeding a storage bank of 132,800uF of filter capacitance. The
transformer itself was designed for extremely good regulation, insuring stable voltages
regardless of the power demands from the amplifier. Its higher efficiency was insured by
using a toroidal design. Additionally, thermal and dynamic tracking of the bias for the
triple-Darlington driver and output stages is provided to insure that the amplifier operates in
its optimal range regardless of the length of time and the level of operation.
All internal point-to-point wiring is OFC and the highest-grade parts, consistent with their
application and voltage requirement, have been used in its construction. In especially critical
circuits, the finest quality film capacitors have been used. Among its other design
improvements are the following:

18,800uF individual power supplier for input stage & pre driver stage

PP.PS.MPE.MPP.MPBM plastic capacitors inside

132,800uF RUBYCON filter for power output stage

DC Servo and OMRON 20 Amp speaker relay protection circuits

ELNA silk capacitors

Precision TVR for bias adjustment

24 beta-matched TO 3 output transistors

1.2kVA shield cover toroid power transformer

5U chassis & rear carry handles

25 Amps NTC Resistor for surge killer & auto delay time shunt relay function

Larger outside double heatsinks of each channel for greater heat dissipation and better
temperature and dynamic bias tracking. Greater thermal stability is thereby insured.

High-quality, gold-plated brass RCA input jacks

24K gold with plastic cover large speaker terminal

2 Distortion(L.R), thermal and limit (overload) indicator LEDs on front panel

DC voltage protection circuit