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without compression but to pull back to a suitable continuous power for sustained
signals such as rail-to-rail feedback.
Although the long-term limiter thresholds are lower for the mid and high frequency
sections (LF +7dBu, MF +4dBu, HF +1dBu), all W8L/Longbow sections are
designed to accept full MA4.2S power on transients...
W8L/Longbow section
Low frequency
Mid frequency
High frequency
How much mains power will I need?
Many touring systems are supplied with inadequate mains power causing the system to
sound like the PA equivalent of a portable radio with a flat battery!
Here are the current consumption figures for the recommended MA4.2S power
amplifier. When used with our standard crossover and limiter settings.
230Vac operation to DX1 limiter threshold, 2 W8L/Longbow sections per ch: 6A
115Vac operation to DX1 limiter threshold, 2 W8L/Longbow sections per ch: 12A
A rack with 9 MA4.2S amplifiers (each driving 2 W8L/Longbow sections per
channel for a total of 12 W8L/Longbow cabinets) will require a minimum of 54amps
at 230Vac and 108amps at 115Vac under typical live sound conditions. We would
recommend 63A at 230Vac and 120A at 115Vac.
Here are the MINIMUM figures for typical racks:
Number of
W8L/Longbow
cabinets
4
8
12
16
* Large racks are often supplied with 3-phase mains - e.g. a 9-amplifier rack may
be wired with three MA4.2S amplifiers per phase and a 12-amplifier rack may be
wired with four MA4.2S amplifiers per phase. The above minimum current figures
may be divided by 3 when a 3-phase mains supply is used.
How should I distribute mains power within the rack?
Normal distribution practice applies – e.g. a 230Vac inlet 63A inlet would be split
into 2 x 32A spurs which would supply the appropriate outlet strips via 32A
breakers.
Remember that, although the transient power demand will be the same for each
W8L/Longbow section (see table earlier), medium to long-term power demand will be
Max continuous demand
1204W
602W
301W
Number of
Minimum current
MA4.2S
for 230 Vac single
amplifiers
phase mains
3
6
9
12
All material © 2007. Martin Audio Ltd. Subject to change without notice.
Max transient demand
2300W
2300W
2300W
Minimum current
for 115Vac single
phase mains
18A
36A
54A*
108A*
78A*
156A*
36A
78A
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