The SI-275 draws more current than a preamplifier's switched AC outlet can safe-
ly supply. Also, your preamplifier may "thump" at dangerous volumes if the
amplifier is already on when the preamp turns on. It is usually best to turn the
amplifier on only when it is needed. The Turn-On Mode selector switch gives you
three options for turning the SI-275 on and off.
Constant - The auto turn-on circuitry is off. The front panel master power switch
operates the amplifier. In is "On", out is "Off".
Audio Sense - The master switch on the front panel must be in the "On" position.
The amplifier is off when there is no audio signal present at either the left or the
right input, but the sensing circuitry is on. The turn-on sensing circuitry looks for
a tiny amount of audio signal present at any of the audio inputs. If it detects a sig-
nal, the amplifier is turned on. Once the audio signal stops, the sensing circuit
waits two minutes, then turns the amplifier off.
3-30 Volt AC/DC Opto-Isolated Voltage Trigger - The master switch on the front
panel must be in the "On" position. The amplifier is off when there is no 3-30V AC
or DC voltage detected at the trigger input. Once the sensing circuitry detects a volt-
age, the amplifier is turned on. Once the voltage stops, the sensing circuit instantly
turns the amplifier off. Voltage triggers can be supplied by Niles automated switch-
ers, some video projectors, some surround sound processors, or something as sim-
ple as a 16 volt AC wall adapter (Niles XF00008) plugged into the switched outlet
of your stereo receiver. DO NOT USE A DC WALL ADAPTER. The long discharge
time of the DC adapter's filter capacitor will delay the turn-off of the amplifier.
If you are using a wall adapter or external power supply to provide the trigger, it
doesn't have to be very large (a minimum current capability of 2.5 milliamps for a 3
volt trigger increasing up to a minimum of 38 milliamps for a 30 volt trigger).