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4.1
PRINCIPLES
OF
OPERATIO
N
The
0-60 has two direct-coupled amplifier cir-
cuits which employ a dual IC op amp and silicon
transistors in all stages. The
CROWN
designed
and
developed circuit represents a level
of
qual-
ity
and
performance presently unequaled in the
field of audio amplifier design.
The dual
IC
op amp is of a low noise type having a
la
r
ge
gain bandwidth. The results of using
it
for the
input voltage amplifier is that a maximum amount
of
feedback is applied reducing distortion to record low
va
l
ues.
Multiple feedback loops are employed to
allow a maximum
of
overall feedback.
The lack of noise is evidenced
by
a typical 20Hz •
20KHz effective input noise of 1.25 u volts which
produces
an
effective 8 ohm output of 80 micro-
micro {pica)
watts.
The
outp
ut
stage is a quasi-complimentary format
employing the
CROWN
class AB+B
technique
which uses
no
bias current in the output transis-
tors. The result is maximum efficiency with min-
imum crossover notch distortion and idling am-
plifier-heat. Thus there
is
no
bias current adjust-
ment,
as
the output circuit is not temperature-
tolerance critical.
In the
new
output circuit, the driver transistors
carry the bias current, while the output transis-
tors serve only
as
boosters. The output transis-
tors
sense
when the driver transistors are de-
livering significant current to the load and take
over and deliver the large load currents.
T
he
output circuit is protected
by
a V-1 limiter
which limits the drive to the output configuration
whenever the output transistors are overloaded.
V-
1 (volt-ampere) limiting is inherently superior
to all other forms
of
protection
as
it
directly
senses
the overload condition and acts instantly
to relieve the overload, acting only
so
long
as
the
overload exists. The result is complete freedom
from program del
ays
with reliability and maxi-
mum safe output power.
Section 4
CIRCUITRY
The power supply is a continuous-duty type. The
main
DC
supplies are full-wave capacitor input
type with a heavy duty bridge rectifier assembly
and computer grade electrolytics.
The 0-60 represents nothing short of the highest
quality in both circuitry and components. It should
provide a lifetime of trouble-free service for the
most discriminating users.
4.2
TEST
PROCEDURES
The
sole
function of this section is to list precau-
tions essential to obtaining accurate measure-
ments when dealing with high-purity amplifiers
such
as
the 0-60.
1.
Use
the proper line voltage, which
is
the
one
for which the amplifier is connected. The
voltage should
be
measured throughout the
testing with a peak reading meter, and
ad-
justed
to
the
RMS
equivalent voltage (to com-
pensate for line voltage regulation errors
during the course
of
the measurements). All
measurements should
be
taken at the power
amplifier's plug.
When
testing for
IHF
music-
power measurements, the line voltage is to
be
set at 120V when the amplifier is
con
-
nected to 120V, (IHF standards). If the amp
is connected for 240V equivalent test may
be
given by applying 240 volts.
2. The load should be resistive, having less than
10
% reactive component at any frequency up
to five times the highest test frequency.
The
resistor should
be
capable of continuously
dissipating the full output
of
the amplifier
while maintaining its resistance within 1 % of
its rated value. The load should employ only
high-current connectors (if any),
and
be
con-
nected to the binding-post output terminals.
All output measurements should
be
taken at
the amplifier output terminals, and not any-
where along the output cable thru which the
load current is flowing.
3.
The input level controls should
be
set to max-
imum for all distortion tests to assure
re-
peatability of all measurements.
21
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