Signal Ground Lift Switch; Indicators; Protect Led; Clip Led - Optimus MT-1500 Installation And Operating Instructions Manual

MT-1500 / MT-3500
Power Amplifiers

5.4 Signal ground lift switch

For safety and to minimize noise, the amplifier should receive its ground from the line cord.
Whenever possible, the signal source equipment should share the same AC ground as the
amplifier. In some cases, however, this may result in a ground loop. If this happens, remove the
ground lift jumper with the rear panel switch. This jumper electrically connects the signal ground to
the chassis / AC ground. If the jumper is removed, the signal ground is lifted and completely
isolated from the chassis / AC ground. Do not remove the jumper if the amplifier and the signal
source equipment are not on the same AC ground.

6. INDICATORS

The amplifier has five LED indicators in each channel: PROTECT, CLIP, -6, -30 and POWER.
These LEDs displays the operating status and warn about possible abnormal conditions.

6.1 Protect LED

When the red PROTECT LED lights red indicates that the channel has overheated, the channel's
output relay is open, and the speaker has been disconnected. This will happen if the amplifier
senses a DC voltage at its output or when the unit is powered up and it is in the turn-on delay.

6.2 Clip LED

A channel's red CLIP LED will light dimly at the onset of clipping and increase in brilliance, as
clipping becomes more and more severe, staying on until the clipping ceases. If the LED is flashing
quickly and intermittently, the channel is just at the clip threshold level, while a steady, bright glow
means the amplifier is clip limiting, or reducing gain to prevent severely clipped waveforms
reaching loudspeakers.

6.3 LEVEL LEDS -6 / -30

The orange -6 LED lights up when the channel produces an output signal of about -6 dB signal
level. The green -30 LED lights up when the channel produces an output signal of about -6 dB
signal level.

6.4 POWER LED

This indicator lights when the amplifier has been turned on, AC power is available and the low-
voltage power supply and fan are operational.
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