Power reserve
Most power amplifier specifications are based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for percussive peaks and sustained bass
notes.
1) Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load.
An electrical technician should check the mains supply vs demand using an
accurate rms voltage meter.
2) If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3) Avoid driving too many W8CS’ in parallel. I would suggest no more
than two so that the power amplifier’s 2 ohm spec is kept in reserve for
musical peaks.
4) Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier in
bridged mode.
Power amplifier gain or level settings reminder
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
Level controls
The front panel level controls should be turned down (fully counter clockwise) until
FOH-to-Amp rack lines have been checked and controllers have been set to suit the
power amplifiers to be used (see Section 3.5). Music should be used to check that
controllers are receiving and sending the appropriate signal bands and then each
power amplifier level control advanced in sequence to check system operation and
patching.
Assuming that controllers have been set as tabulated in Section 3.5, power amplifier
level controls should be set to full (fully clockwise) for loudspeaker sections requiring
the strongest drive. Amplifiers driving nearer-field sections within the same cluster
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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