Crown DC-300A - 5.4 DISASSEMBLY FOR SERVICING; 5.4.1 REMOVAL OF FRONT PANEL AND CHASSIS COVER; 5.4.2 REMOVAL OF CHASSIS COVER ASSEMBLY

40
R, R,
LOAD R,
30
RESISTANCE DAMPING
(ohms) FACTOR
100
20
50
cy
«
15 ry, & 20
KY
of4+
Ve
»,
ry o 10
w/t
fe
We
we 4
10 ry, ‘3
w/e
9 ~
°
e 2
8
7 1
6
04 8000
5000
06 Ry
SOURCE {A/1000 f+.) ANNEALED
a
RESISTANCE woooy COPPER
(ohms) 2-COND. 500 WIRE
2 CABLE (AWG)
(feet) —~# 28
100
4 5 ——# 26
10 50+— #24
6 20 ——-#22
50 we
1 AOD oD #8
200 — #16
5+—#14
2 aoe — #12
1000 =—
2000 vr
4 5000 —#6
5+—#4
6 —#2
—#0
ie —#00
1—¥# 0000
.05
20
01
40
FIG. 2-4
SOURCE RESISTANCE AND DAMPING FACTOR VS. LENGTH AND SIZE OF OUTPUT LEADS
is provided for wire selection. For dynamic moving-coil
loudspeakers the value of R, should preferably be that
measured by an ohmmeter across the voice coil, rather
than the manufacturer's rating. For electrostatic speak-
ers and such, the manufacturer's rated impedance should
be used for R.
If the load (matching transformer, inductance, or full-
range electrostatic speaker system) appears as a short-
circuit at low frequencies, a large non-polarized
capacitor (paralleled with a resistor) should be placed
in series with the load.
For electrostatic speakers (if the manufacturer has not
provided a capacitor) an external non-polar capacitor of
590-708 mfd and 4 ohm power resistor should be placed
in series with the plus (+) speaker lead. This will pre-
vent large low-frequency currents from damaging the
electrostatic transformer or from unnecessarily
activating the DC-300A‘s protective systems. An ef-
fective test to determine if such parts are needed is to
4,20W
From
Amp | (7— “Full, Range
Output a>
P 590-708 yt l nH pas
110 VAC, NLP. => Suing ne.
| yo blocking
x? capacitor)
GND
FIG. 2-5
SCHEMATIC FOR FULL RANGE
ELECTROSTATIC SPEAKER CONNECTIONS
measure the DC resistance between the output terminals
with an ohmmeter. If the resistance is less than 3 ohms,
the parts should be added as shown schematically
in Fig. 2-5.
When selecting connectors for the output lines, the follow-
ing general precautions apply (with all power connectors):
1.
A
male
plug,
carrying
signal,
must
not
be
on
the
far
end
of
the
line
where
it
can
be
exposed,
giving
rise
to
both
shock
and
short-circuit
hazards.