Niles®' Systems Integration Amplifiers® are powerful tools that simplify and optimize complex custom multi-room installations. While traditional receivers and amplifiers work well in typical stereo and home theater systems, multi-room systems require an amplifier that does more than just drive speakers — these systems require an approach that offers greater flexibility and performance.

The SI-275 stereo amplifier gives you 75 high-current watts RMS per channel, which makes it ideal for use with outdoor speakers. It's also 4-ohm stable, so you can safely connect two pairs of 8-ohm speakers in parallel.


  • discrete, high-current design
  • 75 watts RMS per channel into 8 ohms (both channels driven)
  • 100 watts RMS per channel into 4 ohms (both channels driven)
  • stable into low-impedance loads
  • three turn-on modes: music sensing, voltage trigger, and manual
  • dual 5-way binding posts
  • 12-volt control output
  • voltage trigger input accepts 3-30V AC/DC
  • detachable AC power cord
  • cascade output lets you easily add another amp to your system
  • left and right channel adjustable level controls
  • DC, short circuit, and overload protection with automatic reset
  • 17"W x 2-5/16"H x 13"D
  • warranty: 2 years

Niles SI-275 Reviews

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Niles SI-275

Written By Steve G, minnesota on Sunday, April 03, 2011

Crutchfield Customer Review (What's this?)

a great addition to my Niles ZR6 system for two pairs of 8 ohm speakers.

Great Amp

Written By Travis, Orlando, FL on Friday, May 22, 2009

What a great amp! 4 ohm load and it runs perfectly. Powers my 4 Atrium 55s effortlessly and they sound great! A separate amp is definitely worth the money!

WOW - Awesome Sound!

Written By James, Richmond va on Monday, May 14, 2007

Crutchfield Customer Review (What's this?)

All I have to say is WOW! This is one amazing peice of equipment. Anyone who has a whole house audio system and doesn't have an external amp pushing those speakers are missing out. I was using the rear surround channels on my HK AVR635 receiver to power my multi-room whole house audio package which included 6 pairs of speakers. The sound volume/quality was alright with the in-ceiling speakers but the outdoor speakers would never play very loud. Not to mention the fact that the receiver was running so hot you could fry an egg on it. With the Niles amp pushing the whole house audio the sound is amazing and those outdoor speakers really came to life. Plus my receiver is now running much cooler. I'm running a 4om load on the Niles amp and the thing doesn't even heat up a a single degree. Awesome! I highly recommend this product to anyone with a whole house audio package.

Hands-on research

What's in the box?

Download owner's manual

  • 2-channel power amplifier
  • 6.3' two-pronged AC cord
  • Instruction manual
  • Safeguards
  • Warranty and registration card

Product Research



Independent power supply: Each channel is powered from its own independent power supply. This minimizes cross talk.

Independent level controls: Each channel has its own level control allowing you to limit the output and to precisely match the amplifier to the rest of your system.

Three turn-on modes: Three turn-on modes allow you to interface with any kind of system and have the amplifier automatically turn on.

Protection Circuitry: Automatic DC, short circuit and overload protection.

Control Output: A 12 volt DC output allows you to operate voltage-triggered devices such as motorized screens and curtains.

High quality parts: Uses 1% metal film resistors, high quality capacitors and oversized heat sinks.


Front panel:

  • Master power switch: turns unit on and off
  • Power LED: Illuminates in red when the unit is connected to AC and the master power switch is on.
  • Active LED: Illuminates in green when the amplifier circuitry is turned on by the turn on circuits.
  • Protect LED: Illuminates in red when the unit is turned off by the protection circuitry.
  • Independent left and right level adjustment screws: Allow you to preset the maximum system volume or match levels with another amplifier using a 1/8" slotted screwdriver (not supplied).
Rear panel:
  • Turn-on mode switch: Allows you to select one of three modes. Constant mode defeats the turn-on circuitry and the front panel master power switch turns the unit on and off. Audio sense mode turns the amplifier off when no audio signal is present for three minutes and on whenever an audio signal is present. 3-30 volt AC/DC Trigger mode turns the unit off when no AC or DC voltage is detected at the trigger input and turns the unit on when a voltage and a line level audio signal is detected.
  • 3-30V AC/DC trigger input: 3.5mm female jack for voltage input. If a unit which outputs 3-30V AC or DC voltage is connected to this input and the turn-on mode is set to Trigger mode the unit turns on when it detects the signal and turns off when the signal stops. Voltage triggers are supplied by some Niles automated switchers, some video projectors or even a 16 volt Niles AC wall adapter (Niles XF00008).
  • 12 volt control output: Female 3.5mm jack. This jack provides a 12V DC signal used for triggering Niles automated switchers, some motorized screens, curtains, etc. When the amplifier is turn off this jack stops sending out the 12V DC signal.
  • Main input: Gold plated RCA stereo input.
  • Main output: Gold plated RCA stereo output (marked Cascade output) which allows you to daisy chain multiple amplifiers. This output is not buffered so if you want to chain more than 5 amplifiers a buffered distribution amplifier like the Niles ADA-6 is needed.
  • Speaker outputs: Left and right gold-plated 5-way binding posts accept up to 12 gauge bare wire or banana plugs.
  • AC jack: For the supplied AC line cord.


Continuous Average Power Output:

  • 75 watts per channel RMS at 8 ohms
  • 100 watts per channel RMS at 4 ohms
  • Minimum impedance load of 2.67 ohms

Input Impedance: 56k ohms

Input sensitivity: .985V for 8 ohm rated input

Overall voltage gain: 30 dB

Frequency response: Bandwidth limited from 10 Hz to 100 kHz

Total Harmonic Distortion:

  • 8 Ohms: .05% THD from 20 Hz to 20 kHz @ full rated power
  • 4 Ohms: .08% THD from 20 Hz to 20 kHz @ full rated power

Weight: 21 lbs.


The manual recommends at least 5" of free air space above the chassis and that, if the unit is placed in a cabinet, that the rear of the cabinet be opened.

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