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Niles SI-2150 Class D Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Niles SI-2150 Class D amplifier. It is on kind loan from a member. He purchased it refurbished and I see it for sale at $367. Original cost seems to be US $850.

By using efficient Hypex UcD250LP class D amplifier modules, the SI-2150 manages to fit in a small, 1U rack chassis:

Niles SI-2150 Amplifier Custom Install Stereo Audio Review.jpg


Niles is targeting this amp as Custom Integration (CI) channel so has good control as far as trigger and such:

Niles SI-2150 Amplifier Custom Install Stereo Back Panel Inputs Audio Review.jpg


In use, the unit stayed cool and calm. When pushed into clipping it will go into protection. Sadly it stays in that mode until it is power cycled rather than recovering on its own.

Nice set of gain controls are provided which lets you get precise channel matching -- something that is rarely the case in many amplifiers. I set them to 29 dB for my testing.

Amplifier Audio Measurements
As usual we start with our 1 kHz tone dashboard into 4 ohm load:

Niles SI-2150 Amplifier Custom Install Stereo Audio Measurements.png


SINAD which is the ratio of distortion and noise versus signal is better than average at 85 dB:

Best stereo amplifie review 2020.png


Signal to noise ratio ranks in the same region:

Niles SI-2150 Amplifier Custom Install Stereo SNR Audio Measurements.png


Frequency response is flat enough in audible band:

Niles SI-2150 Amplifier Custom Install Stereo Frequency Response Audio Measurements.png


Power into 4 ohm shows good noise and distortion:

Niles SI-2150 Amplifier Custom Install Stereo Power into 4 ohm Audio Measurements.png


Lots of power is available if we allow the distortion to rise to 1%:

Niles SI-2150 Amplifier Custom Install Stereo Max and Peak Power into 4 ohm Audio Measurements.png


Response into 8 ohm load is rather odd:

Niles SI-2150 Amplifier Custom Install Stereo Power into 8 ohm Audio Measurements.png


Usually we have a declining graph with hard clipping in solid state amplifiers, not this gradual rise in distortion. As such, it was not easy to determine the clipping point as I normally do.

Typical of class D amps, the relationship with frequency and power is complex:

Niles SI-2150 Amplifier Custom Install Stereo THD vs Frequency vs Power Audio Measurements.png


Removing my ultrasonic filter allows us to see the switching spectrum of the amplifier:

Niles SI-2150 Amplifier Custom Install Stereo 1 kHz FFT Audio Measurements.png


Conclusions
I am not sure at the regular list price but at refurbished cost, this is a steal of an amplifier. Lots of power in a cool, small enclosure with above average distortion and noise.

I am going to put the Niles SI-2150 on my recommended list.

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

Don't have an ounce of creativity at the moment to tell you anything sarcastic. So let's cut to the chase and ask you to donate what you can using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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amirm

amirm

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Thread Starter #3
When you say "above average distortion and noise" my brain translates that as "higher distortion and noise" whereas I think it is supposed to be "better than average noise and distortion". Is it just me?
Good feedback. I clarified such.
 

777

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#6
Which is the reference, at 0dBr, in volts, for the graph with switching spectrum ?
 
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#7
Quite high noise, quite high distortion, high order distortion components spread up to the end of audio band. I do not understand why this is a recommended component. Just because it is a Class D??
Performance to cost ratio (at sale price) I think
 

tomtoo

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#9
Quite high noise, quite high distortion, high order distortion components spread up to the end of audio band. I do not understand why this is a recommended component. Just because it is a Class D??
0.006% thd quite high? But who cares in this regions about thd?
At the end it looks like a package that delivers what it is build to. And this with a acceptabel bang for the buck. So give me a reason why @amirm should not recomend ?
 

KEW

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#12
I submitted this unit for measurement.

Note to mod's - I hope I am not violating any forum rules by linking to Crutchfield. My intent is to use Crutchfield as a well-established source for pricing reference.

Thought I might back-fill some info on the unit.
In late June of this year, the price was $430 delivered via Crutchfield for a new unit. I don't remember what the MSRP was.
Currently there is no price listed, but Crutchfield shows new stock is expected 11/30/20.
https://www.crutchfield.com/p_190SI2150/Niles-SI-2150.html

Just for further information on pricing, here is it's "little sister" which looks to use the same case, but have no idea how close the design is.
The MSRP is $659 and Crutchfield's price is $349 (new unit), representing a 47% discount.
https://www.crutchfield.com/p_190SI2100/Niles-SI-2100.html


I was disappointed to see most of the power measurements fall short of Niles specifications (although it does look like their spec's may hold since they are using a whopping 0.2 for THD ... and no THD spec for 4 Ohm value). Here are Niles' specifications:
  • 150 watts per channel into 8 ohms (20-20,000 Hz) at 0.2% with 2 channels driven
  • 270 watts per channel into 4 ohms
  • channels are bridgeable to 550 watts RMS (mono) into 8 ohms
  • bridgeable high-current design handles unusual and reactive loads with ease
  • cutting-edge digital power supplies (one for each channel to eliminate crosstalk)
  • 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
The things I like about the amp (as the user) are:
1) Lightweight - 10.7 lbs.
2) Stays cool w/o fan (to be clear, it does not have/need a fan)
3) Low profile w/nice look (IMHO)
4) Comparatively inexpensive
5) Efficiency - could run several of these without needing to add circuits (and reduced impact for climate change)

That said, it is nothing exceptional, just competent at the basic function of providing amplification.

As far as competition...

The XTZ Edge A2-300 for $500 appears similar in many respects (Uses ICE power modules instead of Hypex - I don't know if one is categorically better than the other)
https://www.xtzsound.com/product/edge-a2-300

However, without ASR measurements it is hard to know how well implemented it is!

Of course, I welcome any discussion on this unit or my comments (I am no expert on this stuff)!
 
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Vasr

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#13
Quite high noise, quite high distortion, high order distortion components spread up to the end of audio band. I do not understand why this is a recommended component. Just because it is a Class D??
Be cheap or be perfect. :)

It could have been worse.
https://www.audiosciencereview.com/forum/index.php?threads/niles-si-275-amplifier-review.12055/
1600442203933.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...​

Anything close to audible?
??? If audibility was a criterion, almost every DAC here would be a recommended component. No?
 

KEW

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#15
"..That said, it is nothing exceptional, just competent at the basic function of providing amplification..."

Yep thas it! Thats cool. Thats why @amirm recomend. Nough said. ;)
I think that is the gist of it!
No one buying this is expecting to get SOTA performance. They are simply hoping for an amp that will not do anything offensive and last many years! I think this delivers on both counts (reliability is TBD, but it really runs cool).
In many ways, it is the equivalent of buying a pro-audio amp without the (somewhat) objectionable aspects of a pro-amp. To this end, it has RCA connections & 5-way speaker outputs, trigger/music-sense options, a clean front panel, and no fan.
With Amirm's measurements to know that Niles didn't "screw the pooch", it seems like a pretty good amp for $430.
 

SIY

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#17
So used within its power and current limits with compliant speakers is this thing ' as good as money can buy ' ?
As long as you define “good” as “creates no audible artifacts.”
 
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amirm

amirm

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Thread Starter #19
Which is the reference, at 0dBr, in volts, for the graph with switching spectrum ?
It is set to the voltage that represents 5 watts into 4 ohm.
 

tomtoo

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#20
Sry today i have a littel to much beer. But this opens up my mouth. Maybe not so good? Who cares?
But we had a diy headphone amp for 500$ @amirm liked. No problem.
But now there is a power amp for the same money. So compare the measurements? Or better not. ;) Still there is complaining. Thats realy funny. A 1w headphone amp for the same money like a 200w power amp. The power amp measures x times better. But people complain that @amirm gives a ok for the power amp. Sometimes i think that tubes have a negative effect on brain cells. Maybe some black magic thats hard to measure. ;)

Edit says: Or maybe some hf feedback quantum radiation that alters brain cells directly??? ;) sry.
 
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