Overview: The Niles Audio SI (System Integration) Amplifiers are
designed to power your custom-installed Audio-Video system. They are constructed
with the finest materials available, including 1% metal film resistors, high
quality capacitors, and oversized heat sinks, that can properly cool the unit
without the need for a noisy fan.
Power Output: The SI-250 stereo amplifier provides 50 watts RMS per
channel at 8 ohms, and 100 watts RMS per channel at 4 ohms with all channels
driven. When bridged, the
output is 225 watts into 8 ohms.
Line Level Input: The amplifier has a single pair of
gold-plated stereo RCA input jacks. If you are bridging the amplifier, you can
connect a mono source (single RCA) to the left-channel input.
Cascade Audio Outputs: The unit's Cascade Audio Outputs
enable you to daisy-chain another amplifier, by connecting the preamp output of
the SI-250 to the input of the second amplifier. The outputs are not buffered,
so if you wish to daisy-chain more than 5 Niles SI Amplifiers, you will need a
buffered distribution amplifier, such as the Niles AVDA-3.
Speaker Terminals: The amplifier is equipped with 5-way
binding post speaker terminals. The terminals will accept single- and
dual-banana plugs, pin connectors, spade lugs, and bare wire up to 12-gauge. For
most applications, 16- or 18-gauge wire is recommended. For wiring runs longer
than 80 feet, 14-gauge wire is recommended.
Multiple Speaker Loads: The SI-250 is stable into very low
impedance loads (minimum impedance is 2.66 ohms in stereo), which means you can
safely operate up to three pairs of 8-ohm speakers directly connected to the
amplifier. You will need to connect a speaker selector switch if you wish to
independently turn on/off connected speakers, or if you wish to connect more
than three pairs of speakers.
Independent Level Controls: The SI-250 has independent left- and
right-channel level controls, letting you pre-set the maximum volume, or
precisely match the volume to the rest of the system. The controls are located
on the rear panel to limit unwanted access.
Turn-on Modes: For convenience, the SI-250 offers three turn-on modes.
Using the 3-way switch on the back panel, you can choose from the following
- Manual Turn-on: The amplifier is turned on and off using the
front panel Master power switch. The automatic turn-on circuitry is turned
off. (Switch position: Constant)
- Music Sense: The amplifier turns on automatically when the
presence of an audio signal is detected on either the left or right input.
When the audio signal is no longer detected, the amplifier turns itself off
after approximately 2 minutes. (The front panel Master switch must be in the
On position, and the Turn-on Mode switch position is set to Audio Sense.)
- External Trigger: The amplifier turns on automatically when a
signal is detected at the 3.5mm AC/DC trigger input. Once the Trigger
voltage is turned off, the amplifier automatically turns itself off. Voltage
triggers can be supplied by a variety of sources, including surround sound
processors, video projectors, and automated switchers. The trigger signal
must be 3-24 volts AC or DC, 20 mA or greater. (The front panel Master
switch must be in the On position, and the Turn-on Mode switch position is
set to 3-30V AC/DC Trigger Input.)
12-volt Control Output: In addition to the 12-volt Trigger Input, the
SI-250 can be used to control other devices using 12-volt triggers, such as
motorized screens and curtains. When the
amplifier is powered on, a 12-volt DC (150 mA) signal is present at the 12V
Control Out 3.5mm mini-jack. (Polarity: tip = +)
Rack-mount Ears: The SI-250 comes with a pair of rack-mount ears to
allow you to mount the amplifier in a standard equipment rack. The rack ears
attach to the sides of the amplifier chassis using the 4 installed screws. The
amp requires only a single rack space (1U) with the feet removed.
Note: A minimum of 7" of free air space must be provided above the
amplifier for proper ventilation.
Removable AC Cord: The SI-250 comes with a 6' detachable,
heavy-duty power cord that allows you to unplug it either at the amp or at the
wall outlet. The amplifier uses an IEC 3-prong cord. The amplifier features an
auto-switching, 110V-230V power supply.