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Niles SI-275 Amplifier Review

amirm

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This is a review and detailed measurements of the Niles SI-275 stereo power amplifier. It is on kind loan from a member. The SI-275 is discontinued. But since it is sold to the custom integration channel, they come up used and in working orders (companies pull out gear wholesale to redo homes). I am told it can be picked up as low as US $100 to $150. I see one on Amazon for US $230. But there is a used one on ebay for $100.

The look is fine:

Niles SI-275 stereo amplifier audior eview.jpg

I like the tall feet on amplifiers to allow for more air flow. A massive heatsink goes the full width of the unit with beefy transistors. Love the fact that it has two trim resistors to balance the gain in both channels. So annoying that these days balance controls are impossible to find yet amplifiers routinely have gain that is different in each channel (causing slightly shift in imaging).

Back panel is simplicity in itself:

Niles SI-275 stereo amplifier back panel audio review.jpg

In use, the SI-275 was solid as a rock. Never shut down. Never complained even when fully clipped. The top of the unit barely got warm despite using traditional class AB amplification. That large and heavy heatsink does a great job of spreading the heat load. Nothing remotely like flimsy heatsinks in mass market stereo amplifiers or audio/video receivers.

Amplifier Audio Measurements
Here is our dashboard:

Niles SI-275 stereo amplifier audio measurements.png


Notice the perfectly matched channels. SINAD is middling but is actually better because distortion is near -100 dB. It is pulled down by power supply noise which due to being low frequency is not very audible. Using what we have, performance is slightly above average:

Best audio amplifier review 2020.png


Noise performance follows the same standard:
Niles SI-275 stereo amplifier SNR audio measurements.png


Frequency response is dead flat in audible band and extends way up:

Niles SI-275 stereo amplifier Frequency Response audio measurements.png


The wider the bandwidth, the more challenging the design (if not done well, the amp can oscillate).

Power into 4 ohm is healthy:
Niles SI-275 stereo amplifier Power into 4 ohm audio measurements.png


Allowing for 1% THD+N, we get even more:

Niles SI-275 stereo amplifier Max and Peak Power audio measurements.png


8- Ohm power is:

Niles SI-275 stereo amplifier Power into 8 ohm audio measurements.png


Response with bot loads is very controlled with no oddities.

Amplifier was stable as soon as powered on and performance did not change much after running for a few minutes (not shown).

Conclusions
The Niles SI-275 is made for abuses of custom integration channel which routinely stuffs amplifiers in places they don't belong (i.e. lack of circulation/cool air). Its construction is well beyond today's mass market product. Measured performance is just above average. Combine these with prices as low as just $100 and you have a great deal.

I am happy to recommend used Niles SI-275. Bargain shoppers rejoice! :)

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As always, questions, comments, recommendations, etc. are welcome.

I know... You think because no one goes out to eat dinner that my cost of living has gone down. But it has not! Plenty of expensive things to buy online. So please don't be stingy and donating what you can using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

pavuol

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Likeable pro manufacturer. For new items, they provide 2 years warranty, which is common here in EU, but not so in US, or?
 

Snarfie

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Can you bridge this amp.
 

martin900

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It would be great if you could also post a picture of the internals.
 

peng

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Power into 4 ohm is healthy:
View attachment 54318

8- Ohm power is:

View attachment 54320

When you said "Better than typical AVR", did you factor in the price for a used unit? 124 W into 4 ohms at 84 dB SINAD is not better than quite a few low cost AVR you have measured so far, such as the AVR-X3500H, RX-A1080, and a couple of Pioneer AVRs if I remember right.
 

ta240

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Is the power supply noise being radiated by the power supply or making it through the power supply?

I notice in the picture in the other thread that the AC wires inside aren't twisted at all and am curious if that would help and maybe a diy shield for the transformer.
 

Xulonn

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Thanks for doing this review, Amir. It helps to "flesh out" the matrix of available amplifiers across by adding another commercial product to the more popular market of consumer products. I probably couldn't tell the difference between this amplifier and my (probably "cleaner") vintage Classé Model Seventy amp.

I am curious about the relatively new commercial audio brand OSD - apparently another U.S. (S. California) brand with manufacturing - where else - in China. The specs and prices look good, but with 20 one star Amazon ratings - mostly for DOA and quickly expiring units, quality and reliability is questionable.

I posted about the OSD XA5180 at the testing "wishlist" thread
 
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Webninja

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Jimster480

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Not bad for $100. I don't think there is anything with a similar price that has overall better performance yet? Correct me if I am wrong.
 

Xulonn

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I would not be so sure about that. The Model 70 is a wonderful design and is class A.

Class AB, actually, and I don't intend to replace it with a Niles commercial amplifier. :cool:

And my only complaint is that you have to open the case to switch from single-ended RCA to balanced XLR inputs.

"All class AB amps run in class A up to a point determined by the level of standing bias/quiescent current, after which they run in class B. The class A output of the Classé Model 70 is approximately 0.19W or 190mW into an 8 ohm load."
 

Willem

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Another benefit is that it has an auto sense on/off option.
 

JohnBooty

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Fortension

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I've picked up a couple of the Sonance amps on eBay. They are designed and built for the same purpose - installers and system integration. Build and sound quality I would expect to be comparable to the Niles. They are generally bridgeable and can have high output - I got a 2x125w for $100 shipped. Some of the their amps are also 2.7 ohm stable.
 

Snarfie

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SEKLEM

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It seems the manufacturer ratings for power on nearly spot on with 75 watts RMS @ 8 ohms and 120 watts RMS @ 4 ohms. Voltage gain is also stated to be 28.5v, that matches the measurement shown here. Manual states "10 hz to 70 khz (-1 db)" Near as can be seen on your graph that appears to be correct as well. Signal to noise spec is off, but theirs is "A-weighted", but I'm not sure what that means.
 

jsrtheta

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As it happens, I just got a 65 w/ch x 3 power amp from Sonance off the Goodwill auction site - came today. Cost $40 plus shipping.

Sounds just fine! And one other benefit of these amps are the line outs, which I believe companies like Niles and Sonance routinely put on their amps for daisy-chaining. Instant sub out! For old 2.1-channel enthusiasts like me, that's a big plus, because a lot of the older preamps and power amplifiers often have no easy way to hook up a sub. (I have a late '80s PS Audio Source preamp as a backup, which allows me to use one set of passive outputs in addition to the regular buffered outputs, but I prefer my outputs to both pass the same strength signal.)

Haven't noticed any problems with PRaT, "air", "midrange liquidity", or cosmic auras either.
 
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