Is this project still active?
I think it's great.
To be able to implement it myself, I unfortunately need (much) more help.
I would like to convert my Echo Dot 2nd generation so that I can tap a digital audio signal. I don't need the internal speaker. I also have two Fire TV Boxes 1st generation, these have a Toslink out, but unfortunately cannot multiroom :-(. Can I install this toslink out in the dot?

Or can I buy a finished PCP which I only have to mount within the echo dot (pherhaps in Germany)?

Great project - last week I ordered 10 PCBs (v4 from your git) - they look very good. As soon as I have all the parts I will solder them. I'll post an update here.

This is great. I'm hoping to do the same, but without the microcontroller. I'm planning on using a hardware controlled PLL multiplier and a different transmitter IC.

I can't seem to find a good way to get the dimensions of your board from the gerbers, would you mind sharing with the cutout locations, that you've found worked for you?

Hi, I'd be interested in knowing which transmitter IC you've picked, because I was struggling to find much in the way of alternatives to the WM8804/5.

I'll have a go a getting the cutout locations shortly, but I've created them by removing the speaker, tracing round it with a pencil, then scanning the result. I then imported that into KiCAD, and placed mounting holes + board outline over the relevant positions. So... not terribly accurate, and a little tricky to describe the exact positions, because I'm not sure what to use as reference points, however I'll have a go.

Ha, that's exactly why I was hoping someone else had worked it out!

I'm planning on using the DIT4096, mostly because the WM parts are less available, and I don't need the (reportedly) better PLL on the receive.
My end hope is to use the SRC4392, so that I don't have to use the dot as clock master. Maybe I'll skip this stage, and just go straight for that.

Also, since opening it up I am a little unsure about the mods to the dot itself as I've not done any SMD stuff. Did you use a hot air rework station?

Interesting, I didn't come across either of those ICs in my searching! The DIT4096 in particular looks like a great choice.

I'm not quite sure what you mean about not using the dot as a clock master, though? unless I'm completely understanding something (more than possible), the dot is always going to be master unless you can update it's firmware/software to get it to operate in slave mode?

As for the mods, yes, I used a hot air rework station (858D) to remove the DAC. This is the first time I've really done much in the way of SMD stuff, so it's the first time I've actually used the hot air for it's proper purpose (instead of, erm, heatshrink...).
For soldering the wires on, my suggestion would be to use some kind of magnification (I used a "MixMart Digital USB Microscope") and copper enamelled wire to make the connections.

Anyway, I've made a diagram of the dimensions I used - it's the dimensions from the one I've actually mounted in the dot (i.e. the one in the photos), and as such, I *know* it doesn't quite fit (case won't close).
Also, I really wouldn't put too much faith in these dimensions... if you use them, definitely print out your design, cut out the mounting holes (which I've just realised I've not included the diameter - they're 8mm), and check it actually fits (!)

dimensions:
https://cdn.hackaday.io/files/1623096944228256/v1-brd.png

I'm currently using a Bluetooth to SPDIF box to bypass the dot's converters. It is connected to a larger setup which I use for Pro Tools. There is a single master clock which drives all the AD/DA converters. To use the dot as a source, I need to switch everything to that as the master clock. This is fixed at 48kHz, and is of lower quality, so I wouldn't want to use it while recording. 

The asynchronous sample rate converter will resample the dot's audio to the Pro tools clock. It's clearly not the purist option (though some hifi people do this believing it reduces jitter), but I'm hoping getting the Bluetooth link of the chain will be a big enough improvement. 

I see, the more advanced SRC4392 makes sense now, interesting set up, good luck :)

Excellent work! This is exactly what I was hoping to accomplish with my project, but obviously didn't get this far. Glad you got the WM8805 clock figured out. I tinkered with various settings on that chip for hours and couldn't make any progress.

As far as the enclosure, I'd love to see someone think up something with a bit more of a premium feel to match its new hi-fi audio chops (aluminum, concrete, etc). I may just have to build one of these and do that myself. 

Solutions for keeping the internal speaker are a bit tricky. A workaround I dreamed of is to put another cheap DAC and amplifier on the board for the internal speaker only and use an esp8266 emulating a wemo switch to switch on and off the amp via voice command. Would be a bit convoluted but would work in theory! 

Thanks; I've played for too many hours as well with the WM8805 trying to get it to do what I wanted on its own, but eventually ended up using a dedicated PLL IC to deal with the clock issue. After that, it pretty much "just worked" straight away.

As for enclosures and audio switching... I did have some plan about some external audio switch that redirected audio based on a 12v trigger from the amplifier (I had similar for the analogue out). But I've taken the easy way out - I've now got two echo dots in the same room. The first with the S/PDIF out has the mic muted, sits out of sight and is set as the rooms "preferred music speaker". The second I use as normal. So, when telling Alexa to play some music, you hear voice feedback about the station, etc. from the second dot, but music is actually played on the first via digital out.

Only downside is that when the amplifier is off, you don't hear any music (but you get everything else). However, I don't think I'd ever really want to listen to music through the Dots speaker, so don't particularly care. It's a bit of cop-out solution, but it's good enough for me.

Great project!