Crown DC-300A Instruction Manual page 3

1.1 GENERAL
mic
FIG. 1-17
DC-300A PICTORIAL
The DC-300A is a dual-channel high-power amplifier for
precision amplification of frequencies from DC to 20KHz.
The unit features extremely low harmonic and intermod-
ulation distortion, very low noise, highest "damping
factor," and quality parts and workmanship. Because of
the large output power, it is possible to obtain a monaural
70-volt balanced line without using an output transformer.
The DC-300A contains a new CROWN developed Signal
Programmed Automatic Current Executor (SPACE
control) electronic amplifier protection circuit which
manifests no flyback pulses, thumps, or shut-down. At
audio frequencies any impedance load including totally
reactive loads may be driven with no adverse effects.
Only maximum output power will be affected by varia-
tions in load impedance. At sub-sonic to DC frequencies
the limiter acts as a VI limiter to provide optimum pro-
tection for the extremely rugged silicon hometaxial
output devices (total! of 16 for a total of 2400W dissipation).
A pair of thermal switches remove power from the unit
if overheating occurs due to insufficient ventilation. The
AC line is fused to protect the power supply.
See Section 3.2 for a description of the protective systems.
The power supply features a 1KW transformer and large
computer-grade filter capacitors giving over 48 joules
of energy storage.
A total of 37 discrete transistors, 1 linear IC (dual op
Section 1
CHANNEL 2
amp), 24 diodes, 1 bridge rectifier, and 3 zener diodes
are used in the DC-300A circuitry. With the integrated
circuit, the effective number of semiconductors is 53
transistors, 34 diodes, and 3 zener diodes.
The output devices, 8/channel, are conservatively em-
ployed, having a total peak current rating/channel of 120
amps in a circuit that is limited to a maximum of 28
amps. Among its unique features, the circuitry includes
the CROWN-pioneered and patented AB+B output con-
figuration.
The input operational amplifiers are powered by two
voltage-regulated supplies. This results in complete
channel-to-channel isolation and independence from line
voltage variations.
Total direct coupling results in perfect, instantaneous,
thump-free overload recovery even on non-symmetrical
waveforms. This cannot be said for any AC-coupled
amplifier presently in existence. Turn-on is instantaneous
with no thumps or program delays.
Front-panel controls include two independent heavy-duty
level controls and a power switch with an associated pilot
light. DC balance controls, which never need adjustment
in normal operation, are located behind the front-panel.