Teardown: Amazon’s fourth-generation echo dot

Article By : Brian Dipert

Amazon claims that its latest-generation Echo Dot's sonic performance supersedes that of predecessors, and independent reviews concur. How'd the company accomplish this audio feat: an improved speaker, enclosure, conversion, processing, etc.?

Within my April 2021 teardown of Amazon’s third-generation Echo Dot “smart speaker”:

I wrote:

The newest fourth-generation model is even more radical in its looks, although given how common it’s seemingly become to bracket-mount Echo Dots to walls, vertically mate them to power outlets, and the like, I suspect the “friendlier” (for such configurations) third-generation model still has a notable life ahead of it.

Aesthetic concerns aside, Amazon focused on enhanced audio quality when introducing the new model in September 2020:

It’s compact, but packs in a powerful 1.6-inch, front-firing speaker, producing crisp vocals and balanced bass for full sound you can enjoy in any room of your home.

So of course, I had to buy one for myself (on sale for $24.99 during Amazon’s June 2021 Prime Days promotions, bundled with a free smart light bulb which I tore down that same August), specifically for teardown purposes. I suspected that the fourth-generation Echo Dot’s greater volume versus its predecessor (the same diameter, but roughly twice the height) would translate into a larger acoustic suspension cavity behind the speaker, the root reasoning for Amazon’s bass-focused sonic improvement claims (with which audiophile sites such as What Hi-Fi? seem to concur).

Let’s find out if I’m right. As usual, I’ll begin with some unboxing shots…starting with the box:

and concluding with a closeup of the bottom-side label:

Time to pop open the top:

The cardboard insert to the right houses the barrel-plug power supply:

With specs as close-up shown:

Underneath our patient are two slim pieces of documentation:

Now for some overview pictures of the Echo Dot (3.9 x 3.9 x 3.5 inches, and 12 ounces), as-usual accompanied by a United States penny (0.75 inches/19.05 mm in diameter) for size-comparison purposes:

Along the back are two connectors; the aforementioned barrel-plug power input, and a 3.5 mm TRS for audio output purposes (in case, for example, you want to tether the Echo Dot to a beefier external speaker instead of using the integrated transducer).

One other interesting (to me, at least) design change from the third-to-fourth generation Echo Dot, revealed in this particular perspective, is that the open mesh covering no longer extends all the way around the unit, in contrast to the similarly spherical Apple HomePod mini:

The resultant sound output isn’t omnidirectional, a fact which Amazon is admittedly upfront about; note the “front-firing speaker” mention in the earlier press release quote.

Turn the Echo Dot upside down and unsurprisingly, you’ll find a circular rubber “foot”

Equally unsurprisingly, from my past teardown experience, peel it off and you’ll find four exposed T6 Torx screw heads underneath:

Here’s a closeup of the still-intact product label, documenting the FCC certification ID and other information details; a manufacturing line test-and-programming PCB-exposed contact point cluster at bottom is also now clearly visible (the purpose of the PCB-exposing round hole at top, which I’ll discuss again shortly, is less obvious to me; reader suggestions are welcomed):

Remove the screws:

and the two halves of the enclosure cleanly and easily separate:

Here’s what the inside of the base looks like:

Note that whereas with past-generation Echo products the status LED ring was at the top of the device, this time it’s at the bottom. The translucent plastic ring “spreads” the LEDs’ illumination more evenly around the base.

Speaking of the LEDs, let’s have a look at the PCB now exposed on the other half…

Note the dozen multicolor LEDs around the circumference. Managing them is a Texas Instruments LP5036 36-channel I2C constant current RGB LED driver, which you’ll find at the bottom of the PCB. To the right of it is a cluster of passive components exposed to the outside by the previously mentioned circular hole in the base…again, reader suggestions are welcome. And above them is a Faraday cage, whose contents are always a curiosity; hold that thought.

At the PCB’s upper left is another Texas Instruments IC, this time the company’s TAS5805M high-efficiency, dual-channel, closed-loop Class-D audio amplifier, which I’m confident is what drives the (mono) speaker. To the right of it is a MediaTek chip labeled MT6398AN, whose function eludes me, despite abundant Google searchingThis teardown’s research results were equally fruitless, but author Brian Dorey suspects that this particular IC is a switching power supply. And below and to the right of it is Diodes Incorporated’s PAM8908 dual-channel 25MW headphone amplifier, which drives the Echo Dot’s 3.5 mm TRS audio output.

Speaking of which…before removing the screws I suspect hold the PCB in place, let’s have another look at those power and audio-output connectors:

And now for those T5 Torx screws:

Hey, I was right! And judging from the thermal tape, I’m guessing there’s a processor underneath this Faraday cage:

Let’s disconnect that ribbon cable to fully free the PCB from its tether:

Speaking of cables…in the process of finalizing this writeup, I came across iFixit’s mini-teardown. Notice that the fourth-gen Echo Dot that they disassembled had two cables between the PCB and the rest of the top-half assemblage; the same ribbon one shown here (which connects to the top-side switches and microphones, along with any associated circuitry for them), and one other, which went to a secondary LED panel. That top-side supplemental LED panel has seemingly been eliminated from my device’s variation of the design. While I’m on the topic of interconnect, note the two electrical contacts on the speaker housing, at the top of the earlier photo. They match up with two contacts on the PCB, at the bottom of that same photo. My guess is that this is how the class D amp on the PCB connects to and drives the speaker.

Back to the PCB:

focusing now on the side we haven’t yet seen unobscured:

At bottom is MediaTek’s MT7653BSN, a combo 802.11ac Wi-Fi-plus-Bluetooth 4.0 controller. You can also see the associated embedded antennas on either side of the PCB, as well as the traces running between them and the IC. And at top, of course, are the power and audio connectors. Before proceeding with the removal of both PCB sides’ Faraday cages, let’s take two more views of them, from a sideways perspective:

And now off with the cages’ tops! Ordinarily, a thin flat head screwdriver would suffice, but these ones were too stubborn for that. Eventually, I first applied my solder-loosening heat gun to them, then the screwdriver acting as a lever arm, which did the trick. First (bottom) side first:

The now-exposed IC is a curious one from a cage-enclosed standpoint: a Kioxia (formerly Toshiba Semiconductor) TC58CVG2S0HRAIJ 4 Mbit serial NAND flash memory. The Echo Dot in Brian Dorey’s earlier-linked teardown used a functionally equivalent chip from Micron.

Flipping the PCB over:

We’re only halfway there:

Time to get the heat gun out again:

And after applying some rubbing alcohol to clean things up, we can see clearly now:

At left is the system’s “brains”, MediaTek’s MT8512BAAV 2 GHz dual-core Arm SoC, which interestingly also integrates Amazon’s AZ1 Neural Edge processor core. Next to it is an obscure-marked Micron chip: thankfully, by cross-referencing with the teardown from Brian Dorey, whose Echo Dot employed a SK Hynix H9HCNNN4GUML, I know this is a 4 Gbit LPDDR4 SDRAM.

Now let’s return our attention to the remainder of the Echo Dot’s top half:

Removing four more screws, these Torx T8, allows us to see both the speaker and the mics-and-switches cluster at the very top of the device:

Let’s focus on the speaker first, since the fourth-generation Echo Dot’s claimed sonic improvements were key to Amazon’s sales pitch:

Here’s a closeup of the markings seen in the previous photo:

Curiously, the speaker itself is the same size as the one in the third-generation Echo Dot (1.6”/40 mm), but if you remove the screws:

It lifts out of place and…a-ha!…the comparatively sizeable acoustic suspension cavity behind it comes into clear view:

Note, too, that I was right (of course ;-)); the cable connected to the speaker also connects on its other end to the earlier-mentioned contacts at the back of the speaker housing.

Last, but not least, let’s look at the insides of the upper shell (the ribbon cable had been glued to the side of the speaker housing, and was easily peeled away):

As previously mentioned, the secondary LED panel mentioned in iFixit’s teardown isn’t present in my Echo Dot. But here’s a closeup of the secondary PCB that is still here:

Remove the screws:

Re-apply the screwdriver-as-lever arm:

Disconnect this end of the ribbon cable:

And we can now see the PCB in all its unobscured glory:

The notable IC on this side of the board is Texas Instruments’ TLV320ADC5140, a quad-channel 768-kHz audio ADC (analog-to-digital converter) which, perhaps obviously, is fed by the four-mic array also visible on this side of the PCB. Flip the PCB over and you’ll first see a gasket:

which easily pops off:

And here’s what the other side of the gasket originally pressed up against: the four switches and the external-sound access portals for the aforementioned four microphones:

Thus concludes this teardown. And having completed it, I’m admittedly kicking myself that I forgot to listen to the fourth-generation Echo Dot (both in an absolute sense and in comparison to the two third-generation Echo Dots currently paired to my Echo Sub) prior to breaking out my implements of destruction. Reader thoughts are as-always welcome in the comments!

 

This article was originally published on EDN.

Brian Dipert is Editor-in-Chief of the Embedded Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

 

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