Additional Load Protection; Ac Power Requirements - Macro-Tech 24x6 Reference Manual

Note: The components shown in Figure 3.12 are com-
monly available from most electronic supply stores.
4-ohm, 20-watt
Resistor
+
590 to 708 µf Capacitor
120 VAC, N.P.
From
Amplifier
Output
–
Fig. 3.12 Inductive Load (Transformer) Network

3.3.3 Additional Load Protection

Because the amplifier generates enormous power, it
may be desirable to protect loudspeakers (or other sen-
sitive loads) from damage due to excessive power. A
common way to do this is to put a fuse in series with the
load. This may be accomplished by using a single fuse
to protect all drivers connected to an output, or each
driver may be fused individually. The nomograph in Fig-
ure 3.13 shows fuse size versus loudspeaker peak
power rating. It can be used to determine what size fuse
to use.
1.0
1.2
1.4
1.6
2
2.5
3
4
5
6
Example:
Impedance = 8 ohms.
7
Peak Power = 75 W
8
Answer: Fuse = 1.5 A
9
10
12
14
16
20
25
30
40
Fig. 3.13 Loudspeaker Fuse Selector Nomograph
Page 16
+
Inductive
Load
–
20
3000
15
2000
10
1500
8
1000
800
6
600
5
4 400
300
3
200
150
2
100
80
1.5
60
1
40
.8
30
.6
20
.5
15
.4
10
8
.3
6
4
.2
3
.15
2
1.5
.1
1
.08
Macro-Tech
Typical fuses help prevent damage due to prolonged
overload, but provide essentially no protection against
damage from large transients. To minimize this prob-
lem, use high-speed instrument fuses such as the
Littlefuse 361000 series. If the loudspeaker is only sus-
ceptible to damage caused by prolonged overload
(such as overheating), use a fuse or circuit breaker hav-
ing the same slow thermal response as the loudspeaker
itself (such as a slow-blow fuse).

3.4 AC Power Requirements

All Macro-Tech amplifiers are shipped with an appro-
priate line cord. When possible, use a power recep-
tacle on a dedicated circuit and always make sure that
it can supply the correct voltage and current. We do not
recommend operating your amplifier on voltages
greater than 10% above or below the unit's rated volt-
age. For example, if your amplifier is rated for 120 VAC,
the line voltage should not exceed 132 VAC. See Sec-
tion 7 for power requirements under a variety of condi-
tions.
All specifications in this manual were measured using
120 VAC, 60 Hz power, unless otherwise noted. Speci-
fications were derived using a voltage that is accurate
to within 0.5% with THD less than 1.0% under all testing
conditions. Performance variations can occur at other
AC voltages and frequencies. In addition, line regula-
tion problems directly affect the output power from the
amplifier.
® 24x6 & 36x12 Power Amplifiers
Reference Manual