The extension cord used to supply power to the “amp rack” should have a third wire safety ground to avoid presenting a safety hazard. We also recommend using a cord that has conduc- tors large enough to avoid severely limiting the amplifier’s ability to supply high currents on transients. With this in mind, we recommend using the following for a fully loaded 15A service:
Extension Cord Length | Wire Gauge |
25 feet | 14 AWG |
50 feet | 12 AWG |
100 feet | 10 AWG |
Power amplifiers can have momentary peak current re- quirements many times above the nominal average current draw. According to
Ohm’s Law, the greater the resistance of the linecord, the more input power is lost between the AC outlet and the power amplifier (across the linecord). And to further aggravate the matter, this relationship is nonlinear. The amount of power lost across the linecord in- creases exponentially as the current demand increases. So if the current demand doubles momentarily because of an exceptionally loud bass note, the amount of AC input power lost across the linecord increases four times. You can see that it is very important to keep the resistance of the linecord to a minimum. That’s why we recommend using a heavy gauge exten- sion cord (like 14 gauge or bigger). Remember, wire gets thicker as the gauge number gets smaller (10 gauge is thicker than 14 gauge).
AC Power Distribution
The majority of AC outlets encountered in homes and clubs are served by a 240VAC cen-
In order to minimize ground loops, the safety grounds for all the outlets should be connected
HIGH VOLTAGE POWER LINE
| 120V |
| |
PRIMARY | 240V | SECONDARY | |
WINDING | WINDING | ||
| |||
| 120V |
| |
TRANSFORMER | EARTH |
| |
240V | GROUND |
| |
(NEUTRAL) |
|
to a common (“star”) grounding point, and the distance between the outlets and the common grounding point should be as short as possible.
If lighting is used in a show, it is preferable to power the lights from one leg of the service, and power the audio equipment from the other leg. This will help minimize noise from the lights coupling into the audio (particularly if SCRs are used).
When setting up for a show, oftentimes you are plugging into an AC power distribution sys- tem you know nothing about. You may even be faced with
If you find that you must plug into a two- wire outlet, you will need to use a
INPUT WIRING
Use a
If you want to build your own cables, refer to the “Connectors” section in Appendix C.
OUTPUT WIRING
Use heavy gauge, stranded wire for connect- ing speakers to the M•1200/M•1400 amplifier’s SPEAKER OUTPUT terminals. As the dis- tance between the amplifier and the speakers increases, the thickness of the wire should also increase. Speaker wire has resistance, and when electricity passes through a resistor, power is lost. The thicker the wire, the less re- sistance it offers, and the more power actually gets to the speakers.
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