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: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: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.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: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: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: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.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:When I tested the SONOS Amp there was a lot of degradation with analog input so let's test that: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: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:Same test with analog input shows a droop at low frequencies as well: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:Let's deal with the most important test: power output versus distortion and noise: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: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:The THD+N versus level and frequency where my new tests show much cleaner results: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: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: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.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: https://www.patreon.com/audiosciencereview ), or https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054 ).