Altec Lansing 9444B - Manual (Page 7)

Operating and Service Instructions for the Altec Lansing 9444B Power Amplifier
Figure 5 High-voltage Distribution System
use, determine the power rating
and load value. Then, select a
standard value fuse of the next
smaller value to the one listed in
the table.
Table П Calculated Output Fuse
Values
Power 4 n 8П 16 n
(wutta) Load Load Lead
100 3-70 2.62 1.85
150 4..54 3.21 2.27
200 5.24 3.70 2.62
300 6.42 4.54 3.21
400 7.41 5.24 3.70
600 9.07 6.42 4.54
The values are calculated for fast-
blow fuses which carry 135% of
their current rating for an hour
but will blow within 1 second at
200%. Other fuse values may be
calculated for different power
levels from the following equation:
Fuse value =
(Pout X ZL)^ amps
ZL
X
1.35
where
Pout is the output power
rating of the amplifier;
and
ZL is the load impedance.
Use 32 volt fuses if possible; they
typically have the lowest internal
resistance which will help mini­
mize deterioration of the damping
factor at the load. Refer to the
example in Figure 4.
3.7 Compression Driver
Protection Capacitors
Compression drivers, used
for mid to high frequency sound
reproduction, are much more sus­
ceptible to damage from low fre­
quencies than large cone loud­
speakers. Even though an elect­
ronic crossover may be employed,
problems may arise in the cables
between the crossover and the
power amplifier, or from raisad-
justment of the crossover. Either
of these situations could apply low
frequency signals or hum to the
driver and cau.se damage. To pre­
vent a potential mishap, Altec
Lansing recommends using a ca^
acitor between the aimplifier and
the compression driver to supp­
ress low frequencies an; ossible
DC. Refer to the exam : e in Fig­
ure 4.
In choosing a value, one must be
careful not to interfere -vith the
crossover frequency. A-: -general
rule, select a сарае:' whose
break frequency, with respect to the
load, is 3 dB down, at approximate­
ly Vi of the high pass comer fre­
quency.
Mylar capacitors witli at least a
100 volt ac rating are rec-.nmend-
ed. Table III shows ‘ e recom­
mended capacitor vnhies for use
with 8 and 16 ohm dri > crs at pop­
ular crossover frequencies.
Table Ш Compre; lí-- ; t fLl
Protection Capacitors
Driver
Crossover 8П 16 n
Frequency Driver Driver
500 Hz 80 ¿I- 40 (iF
800 Hz 50 nl- 25 irF
1000 Hz 40 цГ 20 p.F
1250 Hz 33 Цр î G n F
2000 Hz 20 jiF 10 liF
3150 Hz 12 цГ 6 piF
6300 Hz 6 jiF 3 (iF
4 OCTAL ACCESSORY
SOCKETS
Two octal sockets permit a
variety of plug-in acc.er -jori^ to be
used with the amplifier Normally,
one “U” jumper is inserted bet­
ween octal socket 8 and 1,
and another betwei:: i ins 7 and 6.
These jumpers must remain in
place for the amplii-rr to operate
when not using ar.‘: accessory
modules. To use with in accessory
module, remove iau save) the
jumpers and insbi]] .he module
making sure the kev >n its center
post aligns with til* ;Toov6 in the
female socket. For operation, refer
to the instructions rovided with
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