Looking to buy a Mi Box for my living room set-up with an old analog stereo amplifier and a 720p optoma HD65 projector. I would get a chromecast but since I need separate outputs for HDMI video and analog audio I am leaning towards the Mi Box.
A lot of the time I would use it solely for audio streaming like a (chromecast audio) with the projector turned off. Will the audio output work with the projector turned off? Anyone have anything good or bad to say about the sound quality of the analog 3.5mm output on the Mi Box?
I've done something similar with a Shield TV. For music, a USB DAC is probably the most attractive option. Something like the Schiit Modi 2 is a good balance of quality and price. However, I can't guarantee that the output stays on if the projector turns off. Somebody who has a similar setup will need to confirm that.
I took the different option of using a HDMI splitter. My HDMI cable splits into a new HDMI connection to my TV and a separate optical link to my audio receiver (I refuse to buy a new receiver every single time a new type of video connection/standard is introduced). So even if my TV is off, the Shield still thinks it has a HDMI connection and sends audio to the receiver. This is irrelevant to any new receivers that would just use HDMI for audio and then pass it onto the TV with a second cable without a splitter box.
Getting a little bit more technical: The quality of the DAC on my receiver (the part of the chain that turns what's digital audio into analogue that a speaker can understand) is pretty high quality and this is why I was happy to send an optical from the Shield to the receiver and let the receiver dictate the quality of conversion to analog.
In your case, I'd probably go with USB DAC I mentioned earlier. Sounds like you may not even have an option of using an optical cable anyway. The quality of going straight from a 3.5mm output on the Mi Box to an old hifi is likely pretty bad, though it depends how fussy you are. I didn't think the Mi Box had a 3.5mm output.
For anyone who's interested in the music side of Android TV boxes and keeps a library flac files or similar, can I point you to the wonderful SB Player which works perfectly on the Shield. There's some teething issues with 24bit audio etc due to a few kinks that are (hopefully) being ironed out of some Android TV platforms but I can play all my music from a server elsewhere in the house on my receiver using my phone as a controller.