I love my Echo Dot. Its seamless integration with Spotify and voice control is perfect for hands-free music jamming. However, I found the audio quality from the analog output (headphone jack) to be definitely NOT up to the standards set by my modest Hi-Fi system and a $30 USB DAC playing music from my PC.
With this project, I have set out to remove/bypass the Echo's internal DAC and associated analog audio circuitry, and connect an external DAC and/or optical audio output to allow for switching out or upgrading to different DACs at my leisure.
As a secondary goal, I'd like to retain the ability to use the Echo's internal speaker for times when the main stereo system is turned off. However, I'd like to make the Echo smarter about the state of the stereo (so that I don't have to either turn on the stereo or unplug the 3.5mm jack in order to hear Alexa's responses).
Proof of concept video below. See Project Logs section for updates.
Since the last update a few things have happened. I ordered the sainsmart dac based on the pcm5122 as mentioned previously, and (I think) proceeded to kill it. I have a new 5122 chip on the way. In the meantime, I have redone the i2s lines to the pcm5122, beefed up the power supply a bit with a little LC circuit made from parts laying around, and put it all inside the case (sans internal speaker). Even this little 5102 dac blows the stock dac out of the water... For less than five bucks! Will be very interested to see how the 5122 with vastly better power supply and analog components will do. The change will be small for sure, but maybe noticeable. We'll see if it's worth 5x the price of the little 5102 board.
Also ordered a WM8804 transceiver board, as the eventual goal is to get a digital signal out to a receiver or dedicated dac. It will be a little trickier as it requires a mclk signal, and I haven't yet figured out exactly what frequencies the Echo's various clocks are at. (If anyone has a decent scope and wants to poke around in their echo, let me know!)
I took the leap! Today I removed the TI DAC3203 IC (datasheet here) from the Echo's motherboard and broke out the I2S lines to a cheap eBay PCM5102A DAC (datasheet here) board. Aaaaand after a little fiddling with the DAC... success! It works beautifully. Demo video below.
- Test implementation of an I2S to S/PDIF conversion IC (this one) to hook the Echo Dot up to a digital home theater receiver or optical input DAC.
- Re-instate the Echo's internal speaker, and somehow make it less clunky to switch between using the internal speaker and the audio output. I'd love to be able to somehow detect the status of the amplifier (hooked up/powered on or off) and switch the outputs with a microcontroller, but it seems like the best solution as of now is to voice-control the switch using an esp8266 configured as an alexa "smart home" device. Looking for suggestions here.
- manufacture a board to add a digital output, and 3D-print a larger volume bottom shell to house the additional board plus the internal speaker.