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Review and Measurements of Amazon Link Amp

amirm

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#1
This is a review and detailed measurements of Amazon Echo Link Amp power amplifier, DAC and network streamer. I purchased this from Amazon for USD $299 and it arrived yesterday.

While rather featureless from front, the overall feel of the plastic and case is quite good:

Amazon Echo Link Amp Amplifier Audio Review.jpg

When you rotate the volume control white LEDs light up to show a coarse volume control. They time out very quickly though so I could not capture them on the camera.

Not sure what the hole is for. Maybe it is for a remote control but none was provided.

The back panel is the more interesting bit:

Amazon Echo Link Amp Amplifier Back Panel Audio Review.jpg

In addition to the power amplifier, we have a nice little DAC and pre-amplifier here. There are digital inputs in the form of both Coax and Toslink S/PDIF. And of course we also have streaming capability with the Ethernet jack and wifi.

Surprisingly we also have S/PDIF and Toslink output for digital connectivity to other DACs and amplifiers.

There is analog input and output. Former can be used for your analog gear and the latter, for use as a DAC or pre-amp. There are issues with this mode though. See later in measurement section.

Operationally the Link Amp runs very cool. However at higher power there is an audible mechanical hissing sound likely caused by resonance of an internal inductor. It was audible to me from 3 feet away without use of speakers (dummy loads).

As you can imagine for a product with Amazon name of it, there is a professional looking label underneath with every regulatory and safety certification you would want to see. This is important as the Link Amp like many other power amplifiers is mains operated with a lot of high power circuits.

Oddly there is no power button.

Sadly there is hardly any documentation provided with the unit. You are supposed to seek help in the Alexa app. I naively assumed that connecting ethernet cable would mean the Link Amp wout get instantly recognized by the app but such was not the case. I had to configure it using Wifi with the mess that is: connecting to local ad-hoc wifi it creates and then using the main home network. Process was quite non-intuitive and took multiple reboots of phone and link amp to get it to finally recognize it. Boy, do I miss the simplicity of the original echo.

Oddly, Alexa app provides no control over inputs! I just fed it S/PDIF and it output that. Ditto for analog. Can't tell what priority it will use if both are active.

There is a volume control in the app but it only controls local/streaming content, not the volume control on the Amp. Really? The volume control is digital so why can't I control it in the app???

Amazon has really lost its way here with respect to software here. Added complexity over time has not been managed.

Also at fault is the computer and networking industry that has not invented a new revision of Wifi standard that just works with devices like this.

Overall, my impression of hardware is positive and software negative.

Anyway, let's get into measurements. With so much functionality here, I have chosen a subset to test, mostly focusing on the amplifier performance.

DAC Measurements
I was happy to see line out so thought we can check the performance of the DAC this way. Alas, this was not meant to be as without a load, the amplifier shuts down when you turn up the volume to max to get the nominal voltage you like to see on a DAC. There should be a software option to turn off the power amp so it doesn't do that. So I had to connect my dummy loads to the amp to test it. Here is the outcome:

Amazon Echo Link Amp DAC Line Out Audio Meaurements.png


The power amplifier reduced performance by about 5 dB. SINAD was 92 dB or so without the load. The current values put the Link Amp in the lower tier of DACs tested:
Amazon Echo Link Amp DAC Line Out SINAD Audio Meaurements.png


It would have gone into a tier higher if I didn't have to run the power amplifier along with it.

Here is the DAC frequency response which was promoted by later test results:

Amazon Echo Link Amp DAC Line Out Frequency Response Audio Meaurements.png


The 44.1 kHz sampling results are fine. What is not fine is that no matter what other sample rate you use, you get the same bandwidth! In other words, while higher sample rates are accepted, everything seems to be down sampled to 44.1 or 48 kHz. So forget any dreams you have of high resolution audio.

Power Amplifier Measurements
Important note before we get into this section: during testing the results were a complete mess at lower frequencies. The graphs were literally not readable with very high variations of THD+N. So I spent a few hours with my son working through it and turned out some of these class-D amps cause frequency modulation at low frequencies which throws off the analyzer notch filter. The result was that THD+N would go from correct value to 20%+ which would totally screw things up on the graph. I found a good work-around for this which made the measurements look a lot nicer. Alas, this means you can't quite compare these results to previous measurements where this issue was visible. Fortunately we had very clean amplifiers such as Hypex NC400 without this issue so those results stand.

Let's start with power amplifier dashboard st 5 watts using digital input:

Amazon Echo Link Amp Amplifier SPDIF Audio Meaurements.png


When I tested the SONOS Amp there was a lot of degradation with analog input so let's test that:

Amazon Echo Link Amp Amplifier RCA In Audio Meaurements.png


Ah, a sigh of relief. Performance actually improves a bit using analog in! Noise floor is flatter and lower although not enough to make the SINAD any different. Putting that value in context of other power amplifiers tested, we get this:

Best Power Amplifiers 2019.png


I updated this graph with the digital input of SONOS which nicely outperforms the Link Amp. However, as noted with analog input the Amazon Link Amp is much better.

Frequency response with digital input shows the same bandwidth limitation that the DAC did:
Amazon Echo Link Amp Amplifier SPDIF Freuency Response Audio Meaurements.png


Same test with analog input shows a droop at low frequencies as well:

Amazon Echo Link Amp Amplifier RCA Freuency Response Audio Meaurements.png


Note that even when using analog input, you are limited to the same 24 kHz bandwidth! Someone didn't want you to mess with high resolution audio no matter what. :)

That aside, there is now a low frequency roll off too.

Here is the signal to noise ratio:
Amazon Echo Link Amp Amplifier RCA In Dynamnic Range Audio Meaurements.png


Let's deal with the most important test: power output versus distortion and noise:
Amazon Echo Link Amp Amplifier RCA In Power Audio Meaurements.png


Compared to other budget amps like the $199 Topping TP60, there is much more power here and at lower noise and distortion. Don't like one channel having more distortion though.

A more direct competitor is the SONOS amp which costs twice as much but otherwise has streaming functionality:
Amazon Echo Link Amp Amplifier RCA In Compared to SONOS Power Audio Meaurements.png


The Link Amp has better noise level but that is because SONOS has poor performance with its analog input. The SONOS has tons more power and its two channels are staying in synch. So the SONOS is a better deal here putting the cost aside. Of course neither comes remotely close to our reference Hypex NC400 DIY build (at > $1,000).

There has been some interest in running jitter tests on these power amplifiers. So here is a snapshot of that:

Amazon Echo Link Amp Amplifier RCA In Jitter Audio Meaurements.png


The THD+N versus level and frequency where my new tests show much cleaner results:

Amazon Echo Link Amp Amplifier RCA In THD versus Frequency Audio Meaurements.png


Note that I have limited the bandwidth to 61 kHz. That is enough to capture the third harmonic of 20 kHz but low enough to keep the ultrasonic noise that these amps have. I will show that in a bit. Here we see that distortion rises with low and high frequencies. The curve though matches how our hearing works in that we are much less sensitive in low and high frequencies so the distortion products are likely not audibly a problem. Note then that testing at 1 khz shows the best case scenario for these class D amplifiers.

I have another variation of above where I sweep the level/power and keep the frequency the same:
Amazon Echo Link Amp Amplifier RCA In THD vs Frequency vs Power Audio Meaurements.png



We see that at 20,000 Hz, the two channels perform the same. But as soon as we lower the test to 2,000 Hz and then 200 Hz, one channel gets a lot worse. This tells me there is insufficient power supply capacitor reserve for one channel than for the other. The lower frequencies are more taxing this way because they stay at their extreme peaks of the sine wave longer.

Lastly, here is our ultrasonic spectrum of a 1 kHz tone:
Amazon Echo Link Amp Amplifier RCA In 1 Khz FFT Spectrum Audio Meaurements.png


We see our sharp spike around 600 kHz indicating that is the switching frequency. The rise in ultrasonics around 100 khz shows noise shaping (pulling noise out of audible band and stuffing it here). Levels for these are quite low as class-D amps go, showing good attention to filtering, no doubt helped with the limited bandwidth of 24 kHz.

Conclusions
Mechanically and from safety and emissions point of view, Amazon Echo Link amp delivers for just $299. This puts it way ahead of many offerings in this price range which are more akin to DIY efforts than a polished product. On top of that, you have streaming, DAC and a digital and analog pre-amplifier. This is a lot and I suspect Amazon is losing money on each one or barely breaking even.

While some attention has been paid to produce a performant product, there are clear limitations and issues here and there. Limiting of the bandwidth to 24 khz in all modes is a miss objectively but not subjectively. As with other class D amps, we have odd behavior here and there such as rise in low frequency distortion, ultrasonic noise.

The mechanical whistling while the amp is pushed should have been caught and fixed although in practice, the music should mask that well.

At $299 with so many features and generally good performance, I am going to go ahead and put the Amazon Echo Link Amp on my recommended list. No, it is no audiophile find. But for secondary use its performance is good enough to make it a good buy.

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

Got a very interesting email from a guy by the name of Ahmad from Nigeria. Says they actually have money trees there in the jungle and he is willing to send me some for free (to get publicity on ASR) if I just provide for shipping and special handling of $2,000. So please donate money so I can buy a few and get rich:

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).
 

Soniclife

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#3
Overall, my impression of hardware is positive and software negative.
I cannot work out of that's weirdly to be expected these days, or the other way around.

Does it work via the analogue inputs even if it's not online? It's good to know as they may make ok amps in second systems even after Amazon has abandoned them in a few years, which I fear they will.
 

Tks

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#7
Very nice review, thanks amirm.

Color me surprised. Didn't think I'd see a recommendation coming out of this thing. I've seen the reasoning as to why of course in the conclusion.

With performance being eh, the egregious subjective aversion I have to operational incessant constants like a humming emanating from the unit (as if it were some desktop part guilty of something like coilwhine under high or low load, and at 3 feet no less), to the preposterous notion a company of this caliber would botch the software side of the UX, to oddities like volume control being digital, but only operational through remote based on I/O of use..

Wrap that up in a plastic case (of which I have no personal distates for, and in very many instances prefer the use of nicely made, and finished plastics for certain uses).

Definitely not my cup of tea with this one. With respect to losing, or breaking even on these. Doubtful is the loss in the long run that they're losing as much as you may feel. Especially with respect to the hook and sinker that entails the "Alexa" ecosystem of AI assitants as the long-term play of hoarding as much data as possible from users under its umbrella of operations seeing as you had to use the app for configuration.

You akin the product to a level of DIY-sort of offering. Well at the scale that Amazon operates, I highly doubt they're paying anywhere near for the parts as a DIY'er might've had to with something of this sort of product caliber. I think the price for the breadth of the featureset is what one would have expected out of Amazon for instance. But likewise with the expectation of anything hardly being remotely considered state-of-the-art.
 

GGroch

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#8
If you are quick, you can provide the 1st owner review of this on Amazon! Nice to see that it is one of the few Class D amps tested so far that seems to meet its advertised power ratings.

Restorer-john, I think that is a system set-up/reset button on the back, not power.

I will be interested to see how well it sells. Readers of ASR are certainly not the target market, but for people who have already bought into Echo voice control for their music streaming, this provides a simple way to power passive speakers that provide a far better experience than listening to an Echo.

On the other hand, you could also just run a cable from the line out on any Echo or Echo Dot (which I guess you need anyway for voice control) to any stereo amp and do about the same thing.

Functionally, I was sad to see that none of the direct inputs (analog or digital) can be broadcast wirelessly to your home's other Echo zones. Some competitors, like the Sonos and Klipsch Powergate let you do that. The Paradigm PW - Amp does not (but oddly the PW/Link preamp does).

Clearly the target market does not care about HD audio sources, and that may be rational. However, there seems to be no easy way to broadcast local content (analog & digital line in, or locally stored digital files) in the Amazon Echosystem ;). Sonos and Play-fi let you do that.
 
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Jaimo

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#10
@amirm, what GGroch said...

Pls post this as an Amazon review. I bet it will get the appropriate attention from the design team. Maybe they will take your comments into account for the next revision.
 

amirm

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#12
Is that a recessed power button on the rear?
As noted, this is a "go into wifi configuration" mode button. Isn't it sad that they have not put labels on such things?
 

trl

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#14
Got a very interesting email from a guy by the name of Ahmad from Nigeria. Says they actually have money trees there in the jungle and he is willing to send me some for free (to get publicity on ASR) if I just provide for shipping and special handling of $2,000. So please donate money so I can buy a few and get rich:
You should probably get there in person to collect the money. :)
 

stunta

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#16
They SAY it doesn't have a microphone. I bet Amazon engineers could fit a lot of sensors into the suspiciously unlabeled "headphone jack" on the front.
Just don't connect it to the internet. Also wrap the device in tin foil and place it inside a Faraday cage. ;)
 

Tks

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#17
They SAY it doesn't have a microphone. I bet Amazon engineers could fit a lot of sensors into the suspiciously unlabeled "headphone jack" on the front.
True, though a company selling a device with a microphone in it, that doesn't act as a user-function in the slightest - would be quite improbable. First off, because someone would eventually open it and find out. Second, the PR fallout would be quite serious and would be grounds for serious invasions of privacy (as the usual defense in the modern day for breaking privacy laws is the fact they are stated in the product manual somewhere that the device had a microphone for whatever purposes).

Though truth be told, the Alexa app's mandatory requirement is all that's really needed in this case. When you have that on your mobile device, that's enough for them with respect to this app. Still, nonetheless deplorable that this device can't get going without said app I presume from reading the review.
 

soundwave76

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#18
They SAY it doesn't have a microphone. I bet Amazon engineers could fit a lot of sensors into the suspiciously unlabeled "headphone jack" on the front.
Agree. I wouldn't be suprised if there is a microphone inside, like there was in the Google Nest product, which wasn't mentioned to the users.
 

GGroch

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#20
I agree it is extremely unlikely there is a mic inside, but considering its primary benefit/reason to exist is voice control that seems quite odd. The Amazon Echo Input (a Chromecast Audio-like device currently on sale for $20) does have a mic. The Fire TV Cube that adds almost any HDMI TV & remote controlled Soundbar or AV component system into the FireTV/Echosystem has 2 mics, one on the cube, one on its handheld remote. Perhaps they assumed the Link Amp would often be hidden in a cabinet or that the attached speakers would often drown out voice commands. I doubt privacy was a motivator.

Even without a mic, if they built an RF remote receiver into the Link Amp to make it compatible with a FireTV-like remote that could add voice control, remote volume, and basic input switching without having to access the app or an Echo device every time.

Just don't connect it to the internet. Also wrap the device in tin foil......;)
This raises a consideration about testing. Every Google/Amazon/Sonos/Play-Fi device I have used downloads one or more firmware updates during initial online setup. In the case of my Paradigm PW-Amp, there were two firmware updates through the Play-Fi app, and at least 1 through the Arc Room Correction app. It is certainly possible that some of these updates impact measured performance. It is probably good practice to connect to the internet and go through the initial online setup before performance tests on these smart amps.
 
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