• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Review and Measurements of SONOS Amp

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
17,424
Likes
14,895
Location
Seattle Area
#1
This is a review and detailed measurements of the SONOS Amp wireless/wired networked amplifier. It was kindly purchased by a member and drop shipped to me for testing. It costs USD $599 and seems to be price protected. This is the second generation amplifier from SONOS. The first one lasted until now from company's beginning.

If you are not familiar with SONOS, they pioneered easy, plug-and-play networked/wireless multi-room audio. They aimed high as far as fit and finish, often compared with what Apple would design if they were in this business. Their offerings became so popular that they took the company public. Alas, they have lost direction in the last few years, missing the boat on voice recognition and smart speakers from likes of Amazon and Google.

Back to the product, from industrial design point of view, it is quite a departure from the original SONOS Amp:

SONOS Amp Wireless Amplifier Review.jpg

Amplifiers don't usually have "pause/play" on them but this one does as it is an end-point in a streaming platform. So music piped to this Amp can be put on pause or played using the center icon. The left set of dots lowers the volume and the right, raises it. What is wrong with the traditional up/down symbols to have needed reinvention is beyond me.

The circle above may make you think it is a subwoofer but it is not. It mates with the bottom of the unit allowing you stack them without much of a seam between them.

The back of the unit exemplifies what happens when the company has too much cash on hand and wastes it on useless things:

SONOS Amp Wireless Amplifier Back Panel Review.jpg

I am referring to the power socket on the left. It seems to be a proprietary connection, mating with a beautifully made power cord. It looks very nice when plugged in but why on earth would I care what the back of the unit looks like in this regard? Granted, the cord is flexible and feels nice in hand when you plug it in. I shutter to think how much it cost to tool the socket and power cord including the regulatory and safety costs. If the final outcome is that if I need a longer cord I have to go to SONOS, they deserve a few curse words on that.

Somewhat similarly there are banana sockets but they are flush and custom made in metal. You are then given adapters like the one I have plugged in on the "LEFT" channel if you want to connect bare wire. The metal banana jacks are very tight and provide a nice secure connection. But again, I hate to think how much was spent on mechanical engineering and single sourcing of these jacks.

For the first time (?) there is analog input and SONOS shows this playing from a turntable in their promotional videos. The jack seems to be smart in that if nothing was connected to it, it would refuse to "play" from that source.

There is a sub output which I like but did not test. Likewise there is an HDMI input but since it does not pass through, I could not test with it.

The paint on the SONOS Amp feels very nice but is a huge smudge magnet. It picks up oil from skin from barely touching it and I could not wipe them clean with a microfiber. You will need some kind of solvent to keep it clean.

There are dual Ethernet inputs. Why, I am not sure. There is of course wireless input. Just plugging the unit in allowed the SONOS app on Android to find it but could not talk to it. I had to push the button on top left to enable it to find it. As is typical here, it immediately wanted to update the firmware in it. Overall, I found the messaging in the app cryptic and uninformative.

The rest of the user interface is also rough as far as usability. Why do I need to "browse" to select the line in as an input? Why is the unit called a "speaker" in settings?

There is airplay support which allowed me to stream content to it from my Roon player. It takes priority over line in so if you are playing from that input, it will be overridden and streaming content will play. While there is a volume control in SONOS app, when you stream using airplay, it takes the volume control from source player. This provided quite a surprise when I streamed 0 dBFS reference tone from my player and watched the power meter in my analyzer peg to max! Thankfully I was not using any speakers connected to amp.

Speaking of volume control in the app, at least on Android, it has very coarse steps to control line in volume. I don't know how this is usable in practice. A single step would go from 6 to 12 watts of output or some such thing. The front panel controls seem to do the same thing (?).

In advanced settings, there is a sensitivity selector from 1 to 6 (?) with 2 being the default for AV components. There are others for itunes, etc.

Browsing local content on my phone was fast and trouble-free.

Measurements
I connected the analog output of my Audio Precision analyzer to Line in and used balanced connection to analyzer/dummy load to measure performance at nearly 5 watts with 4 ohm load (280 milliwatts output level from analyzer):


SONOS Amp Wireless Amplifier Measurements.png


This is pretty disappointing. Looking at the FFT spectrum we see that the distortion products are below 100 dB yet our SINAD is only 67. This tells us that the SINAD/THD+N is dominated by noise, not harmonic distortion. We can verify this by separating the two in the Audio Precision analyzer:

SONOS Amp Wireless Amplifier THD vs THD+N Measurements.png


The figure on the left includes THD+N meaning it has both Total Harmonic Distortion (THD) plus Noise. Using signal processing we can separate the THD out of it and compute that part as shown on right. As we see, the THD component is 1/6th of the total, confirming that noise is our enemy here, not distortion.

Thinking that the line in may be different than digital streamed content, I used Roon player to stream the same 1 kHz tone to Amp and got this (ignore Gain):

SONOS Amp Wireless Amplifier Streaming Measurements.png


Wow, quite an improvement! How is this possible? In the streaming scenario, a full amplitude digital file is played and volume is controlled in software. In other words, the front-end of the unit gets full signal. In the case of Line in, I am keeping the volume at max and lowering the input level to get to same power output. So it seems that the front-end noise is an issue for Line In.

Using full amplitude of 2 volts we still get rather disappointing performance:

SONOS Amp Wireless Amplifier SNR Measurements.png


85 dB? This is far worse than CD (96 dB).

Frequency response of Line In gives us clues as to what is going on here:
SONOS Amp Wireless Amplifier Line In Frequency Response Measurements.png


We have a very sharp brickwall filter at around 20 kHz. It is causing peaking/attenuation in the "transition band" depending on which channel you look at. It is clear they are digitizing the input but why use such a low sampling rate? Aren't turntable folks going to get upset that you can't even reproduce 20 kHz cleanly?

On the low end, there is a drop but part of that is because I had to select AC input which puts a 10 Hz high-pass filter. Measurements with DC input on the analyzer completely confused the measurement system (due to input DC offset?).

Power measurement using 4 ohm load produced this:
SONOS Amp Wireless Amplifier Power Into 4 Ohm Measurements.png


SONOS rates the Amp at 150 watts into 8 ohms. Here we are seeing over 200 watts of power using 4 ohm which is excellent. During the test I could barely detect the Amp getting warmer so efficiency is quite high. Alas, so is the noise level. Again, this is using Line In with its higher noise level. Best case though at maximum power is in entirely different category than our reference quality Hypex NC400.

Wideband FFT spectrum give us insight into operational design of the unit:
SONOS Amp Wireless Amplifier 1 kHz FFT spectrum Measurements.png


We see a peak in noise at nearly 98 kHz. This "smells" like a power DAC running at that sample rate. Therein lies the issue with power DAC (or "digital amplifiers") in that their switching frequency is very close to audio band unlike class D amps which switch in hundreds of kilohertz. Peak level is -53 dB which indicates good filtering.

Line input (in red) shows secondary anomaly. It has a peak at 21 kHz. Guessing what is going on, there is noise shaping in the ADC which explains the rise prior to that frequency. And then some kind of sharp filter to cut off everything after that.

Conclusions
It seems to me that SONOS has partially lost its way, overspending on mechanical engineering, and underspending on features people really wanted (e.g. voice control). Usability of the software is worse than I expected just the same.

Line in input is really poorly implemented. I don't know why any self-respecting turntable fan would want to use it. It might come in handy though to route TV sound through it that way.

The highlight of the unit is copious amount of power at 4 ohm in such a small and cool running package. I am not sure there are many options in the market with so much power.

Subjectively, that great amount of power may cover the sins I am seeing elsewhere. Objectively though, I would have wanted to see more engineering go into unit to keep its noise level at bay, than making fancy power cords for it.

Overall, I am going to leave the SONOS Amp without a recommendation one way or the other.

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

Weather is supposed to get warmer so I am thinking of cleaning up the RV to get it ready for trips and need money for Diesel fuel. So I am going to pass the had to collect some money using:
Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 

folzag

Member
Patreon Donor
Joined
Jul 24, 2018
Messages
42
Likes
47
#3
features people really wanted (e.g. voice control)
IMHO, pointing out voice control of all things is not a fair criticism.

Voice control electronics are cost prohibitive on a consumer device. Instead, to the chagrin of anyone that cares about privacy, and to the horror of those who didn't care until it was too late, voice control is done by always listening and recording, then performing signal processing on a remote computer system, which Google and Amazon are uniquely able to build out and leverage into additional revenue sources... like selling to advertisers of the products you and yours may be talking about purchasing.
 

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
6,249
Likes
2,296
Location
Riverview, FL
#4
Joined
Dec 1, 2018
Messages
15
Likes
5
#5
Thanks for this interesting review!

Some remarks. My sonos connect also has an analogue line in. The old amp also has one I believe. Not sure if they will be able to play phono imput.

My sonos connect is gathering dust as I got really annoyed with the software. The need to register, crashes, and increasing focus on the sonos ecosystem became annoying. Never used sonos speakers, only used it to stream from my nas. I switched to a raspberry pi, volumio streamer. This is more stable and flexible and plays high res, in contrast to sonos. Volumio interface is less slick and gapless playback does not work from nas for me though.
Does this unit play higher than cd quality?

I do not understand why the noise is an issue. If it is 100 dB down, it will be completely inaudible, not? Am I misunderstanding the measurements?
 

andreasmaaan

Major Contributor
Patreon Donor
Joined
Jun 19, 2018
Messages
2,622
Likes
1,717
#7
Is this a true “power DAC” or rather an ADC-DSP-DAC-amp? If a true power DAC, that is very low distortion.
 
Last edited:

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
1,568
Likes
2,056
Location
Gold Coast, Queensland, Australia
#8

SchwarzeWolke

Member
Patreon Donor
Joined
Feb 7, 2018
Messages
76
Likes
61
#10
So beside the problem with the "line in", if I want to use only the streaming part of this amp, would this be a decent choice?
We already have some speakers from Sonos and I really like the "always on" feature with all of their products.
 

PuX

Member
Joined
Feb 16, 2018
Messages
71
Likes
30
#11
I'd like to see some simple stereo amplifiers measured, if someone offers to borrow them for testing.

it's likely that they will perform a lot better than receivers, dac combos, network players with amps etc. main reason - they only have one purpose so they should be good at it.

for example something like NAD C355/356 or similar <$1000 amps. also curious about expensive brands ones like Densen or Naim.
 

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
6,249
Likes
2,296
Location
Riverview, FL
#12
I'd like to see some simple stereo amplifiers measured, if someone offers to borrow them for testing.

it's likely that they will perform a lot better than receivers, dac combos, network players with amps etc. main reason - they only have one purpose so they should be good at it.
The amplifiers measured here so far have exhibited less than "near perfect" measurements.

First example I found:

https://www.audiosciencereview.com/...easurements-of-dayton-audio-apa-150-amp.6571/
 

Darwin

Active Member
Joined
Oct 11, 2017
Messages
144
Likes
30
#13
I’ve been using one of these for 3 or four months.
I’ve done the A.V. receiver thing and wanted simple and minimal cables while knowing what I was giving up for that.
I use it with a sonos sub although you can use it with any sub. Rear sonos ones and front speakers are Revel Concerta2 M16’s. It’s pretty good for surround sound and has a simulated center that works pretty well. You can also use dialog enhancement which works well. This is designed to be used for home theater which is why it has an hdmi port. All of this works well for me and I like the simplicity. I won’t use a sound bar and the amp gives me a lot of flexibility to do lots of different things.
I turn off the rears and set my Apple TV to stereo for Pandora and Apple Music or Roon.
My main speakers for music are Kef LS50 wireless but music still sounds really good with the Revels.
To be clear the amp does Airplay 2 not just airplay. Sonos adopting airplay was very smart of them. It made their devices much more useful. It also means I never have to use the sonos app. I use an iPhone and don’t have the volume adjustment issues you speak of. I can use it for multi room with all my airplay 2 devices. I’m running a set of stereo paired Homepods in one room, paired sonos ones in the garage, and paired sonos ones on my back porch. I can just select what I want from the home screen of my iPhone and never touch the sonos app.
I don’t get your complaints about the rear being over engineered. I like it like that and the amount of attention to detail. I don’t mind paying for it.
You can easily get a replacement power cord as someone has already mentioned.
The two Ethernet ports are so you can daisy chain a device if needed. Not sure why that is hard to figure out or google.
I’ve been curious to see you review this device, have been a little dissapointed at the results, and it’s put a damper on my idea of maybe connecting a turntable.
Sonos has not missed the boat on voice control at all and I’m surprised you are unaware of that. Several have mics for voice control and currently do Alexa, Siri, and soon Google assistant. Older devices work with an echo. Sonos makes a huge point of voice control so I really have no idea why you made this assumption. It’s all over their web sites and quite well known.
The measurements are what they are but I’m not too impressed by your approach to this review.
 
Last edited:

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
17,424
Likes
14,895
Location
Seattle Area
#14
IMHO, pointing out voice control of all things is not a fair criticism.
It is exactly where the consumer market has gone. And a much better way to interact with a UI-less device when you want to pull up the music you want to listen to. Amazon has sold in excess of 100 million such devices proving the high desirability of such feature. Taking out your phone, unlocking it, then trying to select another piece of music is not remotely as efficient.

Voice control electronics are cost prohibitive on a consumer device. Instead, to the chagrin of anyone that cares about privacy, and to the horror of those who didn't care until it was too late, voice control is done by always listening and recording, then performing signal processing on a remote computer system, which Google and Amazon are uniquely able to build out and leverage into additional revenue sources...
It is actually not that expensive to do local recognition considering how expensive these products are, and the lower cost of DSP and memory. Cloud based systems are better because they can constantly evolve and use much larger data-set to improve recognition.

Regardless, Sonos is a public company and has an obligation to guide the company in a profitable manner and that calls for advancing the platform to better match what the consumers want. They sat around in their box instead of innovating beyond.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
17,424
Likes
14,895
Location
Seattle Area
#15
Sonos has not missed the boat on voice control at all and I’m surprised you are unaware of that. Several have mics for voice control and currently do Alexa, Siri, and soon Google assistant. Older devices work with an echo. Sonos makes a huge point of voice control so I really have no idea why you made this assumption. It’s all over their web sites do quite well known.
I am very well aware of them integrating other voice controls into their products after the fact. This was their market to own. By licensing third-party feature for voice control, they no longer have a differentiation. Every company can and is licensing the same and building smart speakers. Competing with SONOS used to be hard. Not so with advent of smart speakers.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
17,424
Likes
14,895
Location
Seattle Area
#17
I don’t get your complaints about the rear being over engineered. I like it like that and the amount of attention to detail. I don’t mind paying for it.
I praised such detail when I commented on the nice feel of the power cord. I question the management decision to spend a lot of money on that, when they could have better engineered the core product. It is a sign of a company not using its resources wisely.

This is a company I have known since inception since my team at Microsoft worked with them to implement our audio formats in their products. We used to hold them up as a great example of how to do computer audio right when talking to just about any small and large audio company. It is under that light that I critique where they have landed where they missed the most important innovation in streaming content to a speaker at home.

When I look at this amplifier and its software, little of that excitement is there anymore that existed when I looked at their first generation product with that very nice, flashy controller.

When I lived in silicon valley, the moment we saw a company started to construct fancy buildings instead of putting the money towards product development, we would joke that their stock would tank and in almost every case they did! Same here. When I look at attention put in a power cord instead of internal design, features and usability of software, I worry about the company.
 

Darwin

Active Member
Joined
Oct 11, 2017
Messages
144
Likes
30
#18
I am very well aware of them integrating other voice controls into their products after the fact. This was their market to own. By licensing third-party feature for voice control, they no longer have a differentiation. Every company can and is licensing the same and building smart speakers. Competing with SONOS used to be hard. Not so with advent of smart speakers.
Are you saying they should have their own voice control not using one of the others?
They are a higher quality speaker than the others except for HomePod, and are probably the easiest to use for voice control with home theater. I can use the mics on my rear sonos ones to control everything or a echo dot. I would expect all of their devices to have mics soon.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
17,424
Likes
14,895
Location
Seattle Area
#19
I do not understand why the noise is an issue. If it is 100 dB down, it will be completely inaudible, not? Am I misunderstanding the measurements?
You are :). It is a common mistake. The FFT does indeed show a noise floor of -100 dB. But that is NOT the actual noise floor. When performing an FFT, you tell it how many audio samples it should use to determine the frequency spectrum. In this case, I am using 32K or 32,000 points. What happens then is that the noise of the product gets spread across 32,000 points. In other words, the noise in each point of the graph is 1/32000 of what it actually is. This is called "FFT gain" and results in some 42 dB of noise reduction!

We use larger FFTs like this so that we can see the distortion products that lie within. It is a powerful technique to find distortion at very, very low levels.

For the "truth" look at THD+N. That is the sum of distortion+noise. Looking at the FFT graph, we see almost no distortion spikes for line in. As such, what is there is dominated by +N or noise. So the noise level is what the SINAD indicates or about -70 dB or so, not -100.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
17,424
Likes
14,895
Location
Seattle Area
#20
Are you saying they should have their own voice control not using one of the others?
They should have added voice control years before Amazon did with Echo. Any focus group testing would have shown the difficulty of trying to find and play music with a smartphone.

This is no different on all the mobile phone companies that missed the boat on smartphones and app stores, letting Apple eat their lunch with iPhone. Where is Nokia now?
 
Top Bottom