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Niles SI-250

Stereo power amplifier

7 Reviews | 5 questions - 10 answers


Our take on the Niles SI-250

When professional installers need versatile and rugged components they can depend on, they turn to Niles. 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 choice of pros since 1978

When professional installers need versatile and rugged components they can depend on, they turn to Niles. 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.

Power and performance to spare

Whether you're using the Niles SI-250 as a part of a multi-room audio system or as the amplifier in your main listening room, you'll find that it delivers plenty of pristine, dynamic stereo power. Its high-current design allows it to handle unusual and reactive loads with ease, including the ability to safely drive up to three pairs of directly connected 8-ohm speakers at the same time. And it's not just all muscle. Niles uses high-quality parts throughout to ensure that you'll always get top-notch audio performance. Independent power supplies for each channel prevent cross-talk interference, ensuring clean, spacious sound. Oversized heat sinks keep the SI-250 cool even when driving heavy loads, eliminating the need for a noisy cooling fan and guaranteeing silent operation. Plus, this amp's beefy toroidal transformer ensures that there's always a quiet, steady stream of current coming.

Installer-friendly features

Niles knows what it takes to stay competitive in the world of custom installation. That's why their amps include features that make them easy to integrate. You get three separate turn-on modes to bring the amp to life, plus a 12-volt DC control output to activate other devices such as motorized screens and curtains. Independent level controls for each channel allow precise volume matching to the rest of the system, and can also be used to limit volume to prevent speaker damage. Handy cascade audio outputs let you daisy-chain mutiple amps together. And you can even combine its two channels into one to give your speakers more juice — a great option for power-hungry outdoor speakers.

Product Highlights:

  • 2-channel amplifier
  • bridgeable high-current design handles unusual and reactive loads with ease
  • power output:
    • 50 watts RMS per channel at 8 ohms (both channels driven)
    • 100 watts RMS per channel into 4 ohms (both channels driven)
    • channels are bridgeable to 225 watts RMS (mono) into 8 ohms
  • toroidal transformer
  • frequency response: 5-25,000 Hz (-3 dB)
  • signal-to-noise ratio: 102 dB (20-20,000 Hz)
  • total harmonic distortion: 0.2% (20-20,000 Hz)
  • three turn-on modes: music-sensing, voltage trigger, and manual
  • gold-plated binding posts spaced to accommodate dual banana plugs
  • 12-volt control output
  • voltage trigger input accepts 3-24V AC/DC
  • cascade audio outputs let you easily connect additional amplifiers to your system
  • independent right- and left-channel level controls for precise volume matching
  • fanless design with oversized heat sinks for cool, quiet operation
  • DC, short circuit, and overload protection with automatic reset
  • front-panel LEDs indicate Power, Active Status, and Protection Warning for easier troubleshooting
  • detachable AC power cord
  • rack mount ears included
  • weight: 10.8 lbs.
  • 17-1/4"W x 2-1/4"H (including feet) x 13-1/2"D
  • warranty: 2 years
  • Our 60-day money-back guarantee

Product performed every bit as advertised. It really changed the sound of my in-wall and ceiling home music system.

HKM, Flanders, NJ

What's in the Box:

  • Stereo system integration amplifier
  • 6' AC power cord (3-prong IEC plug)
  • 2 Rack-mount ears
  • Installation Guide

Niles SI-250 Reviews

Average Customer Review(s):

(7 Reviews)

Just as advertised

HKM from Flanders, NJ on 9/14/2016

Crutchfield Customer Review (What's this?)

Product performed every bit as advertised. It really changed the sound of my in-wall and ceiling home music system.



Great Amp

Neal R from atlanta, GA on 1/22/2016

Crutchfield Customer Review (What's this?)

Great Amp! I'm using it to power my Klipsch reference bookshelf speakers and the difference is huge. The sound is significantly cleaner than my previous setup. Very easy to setup



great with Sonos Connect

rk from brooklyn on 10/23/2015

Crutchfield Customer Review (What's this?)

I'm using this with a Sonos Connect to power a set of in-wall speakers. Sounds amazing (much better than my more expensive receiver that recently quit working). No heat. Turns on automatically. Very happy with this purchase

Pros: Low cost solution. Simple set up. Ample power. Sounds great

Cons: N/A

Niles SI-250

Niles SI-250 from South Carolina on 5/18/2015

Crutchfield Customer Review (What's this?)

Terrific piece of stereo equipment. I am very satisfied with my purchase.



Niles SI-250

Tom from Kenosha, WI on 7/31/2014

Crutchfield Customer Review (What's this?)

The Niles SI-250 is an excellent choice. Very easy hook-up, great power, with VERY small profile its is bridgeable if needed. It run very quite and stays cool during operations. I am using it to boost power for my zone 3 outside, and another one in my basement for a zone 2 in my shop.

Pros: Easy hook up, runs cool, and quite no buzzing

Cons: None

Niles SI-250

Brady from Denver, CO on 6/26/2014

Crutchfield Customer Review (What's this?)

1ST class, if you are audiophile. runs cool, sharp, crisp, good base. used with 20yr old large Infinity bookshelve speakers to add to NHT towers with Peachtree Inova, integrated. I think it best to power all equipment down with the surge protector. The twist on, reusable, mini banana plugs, Crutchfield sells, are a plus. Speaker wires can pull out of plug. If power can be switched on, disaster, is possible



Niles amp bridged for center channel speaker

jk47 from Morgantown, WV on 7/20/2013

Crutchfield Customer Review (What's this?)

I bought this amp because it was bridgeable and gave 225 watts for my center channel speaker. I recently bought an emotiva upa200 for my L and R channels and wanted something for my center. This amp looks nice and runs cool. Right away I noticed my center channel had opened up. In watching movies, voices sounded very accurate and possibly and bit heavy on bass. It wasn't sloppy bass so I kind of liked it. Once I ran my auto config for reverb on my Pioneer vsx-52, which I use as a preamp, the extra bass went away and voices sounded impressingly accurate. Dynamics were amazing and rivaled, if not surpassed to upa200 (even though it's not really fair to compare, it's more of a complement to both). The mids were present and the noise floor was impressive. The amp never sounded stressed and highs were always silky and controlled, not harsh or bright at all but pretty near perfect in my opinion (and I'm picky). For music, the same was true, the soundstage was deep, interesting, dynamic and tonally accurate. I have this driving a Paradigm Center 1 Monitor series and am very satisfied for the price.

Pros: -Ample power -Audiophile worthy sound -tonally accurate and interesting (dynamic) sound -good price -sturdy build quality (always runs cool)

Cons: none


Hands-on research

Product Research


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 modes:

  • 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.

Our Product Research Team

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Q & A

Customer Q&A

Crutchfield asked  
Why did you buy this?

Meets my needs and price looks very favorable. [ HERBERT  Aug 26, 2016 ]

5 questions already asked

I do not know the answer to this question. My guess would be yes and give it a shot without buying the second unit. [ Ramon  Aug 30, 2016 ]
Yes! You are about to split the source and go to two separate amplifiers. I would however suggest getting a speaker switch. It allows you to select different "zones" in case you don't always want to use both [ Richard  Aug 26, 2016 ]
That is definitely not normal. [ Guest  Jun 29, 2016 ]
No. This does not happen to me. You might want to turn down the volume before turning the amp off. [ Ramon  Jun 28, 2016 ]
Sorry I have not experienced that issue. [ VIRGINIA  Jun 28, 2016 ]
The popping noise is not common. I am not an electrical engineer, but I imagine that this popping noise is not good for your speaker. I have my amp set to automatically turn on and off when it detects signal going through the system so that I do not have to manually turn it on or off. It does so fairly smoothly with no other popping noise. As I said, I am not an electrical engineer, but maybe you have a grounding issue and you need to ground this unit to the receiver. Either that, or somehow there is an issue with the cable from your unit to the speaker, where the signal might be touching a ground source. Good luck! [ Steven  Jun 28, 2016 ]
SI-250 is a 2-channel power amp. the RX-V475 must have 2-channel "pre-amp" output rca jacks to connect to SI-250. If the DA converter contains pre-amplifier outputs, then you will by pass the RX-V475. the SI-250, or any power amp , will then connect to the speakers, from a "pre-amp" source. Try google of topic. [ BRADY  Jul 22, 2015 ]
This is not a digital amplifier, you will need a separate pre-amp for it to power digital sources such as streaming music. You might want to try and use your Yamaha as a pre-amp for the Niles amp and then run your streaming music a through a Sonos connect. [ MICHAEL  Jul 21, 2015 ]
Niles SI-250 is not wireless. Input is RCA left and right from amp/receiver and output wire from Niles to speakers [ BRADY  Apr 07, 2015 ]

Looking for more? Check out the next model in this lineup.

Niles SI-2100

Get more power for bigger jobs

The Niles SI-2100 offers these features:

100 watts per channel at 8 ohms

220 watts per channel at 4 ohms

400 watts bridged mono at 8 ohms

a cutting-edge digital power supply