Hi Guys,
This is my first post so please go easy 
I’ve looked about the forum for this answer but can’t find any other posts.
If I wanted to plug the Raspberry Pi into a Bose Soundlink Mini would I need to connect a DAC to the Pi or an Amp? whichever one it is has anyone got any reccomendations?
I want to be able to stream music via Airplay to the Pi.
Thanks
Wax1
No need for an amp, there’s one built into the Soundlink. You could start by just connecting a 3.5mm male to male cable between the analog audio output of the Pi and the Soundlink. For better quality audio, you can get an I2S DAC like the IQAudio Pi-DAC+ and then use either the headphone output of the DAC or a different cable to connect the RCA connector outputs to the Soundlink. I’d start with the simpler solution first though and see how it sounds. I have two IQAudio DACs and they are awesome for $45.
That’s great, thanks for the advise.
So, what if I decided to get a amp that connects to the pi zero (preferably a single board like the dac you suggested), could I just plus passive speakers into the amp and that would work? If so, what would the sound quality be like? The only reason I ask is that eventually I want to build a aluminium case that will enclose the pi zero and a amp and just connect the speakers at the rear of the enclosure, maybe eventually add a display and button.
I’m in similar position as @wax1 with a Volumio/Pi headphone socket plugged into a Bose system (Wavelink) via RCAs. In my case, the sound quality is fine without a DAC.
However, I’ve noticed that the audio level from the Volumio/Pi headphone socket is much lower than the built-in Bose FM radio. This means switching from Volumio/Pi to the radio is VERY VERY VERY LOUD AND ANNOYING TO THE WIFE unless I remember to turn down the Bose volume first 
Would a DAC increase or decrease the Pi output level?
Yes, you just connect passive speakers directly to the amp outputs. Look at the info HiFiBerry and IQaudio post on their websites for their amp boards (designed for RPi 3) for more info and examples. I don’t know if similar boards exist for the zero. Or use a DAC board and a separate amplifier (you are then not limited to what is available in ready to connect Pi boards).
For sound quality, “it depends” - on speakers, listening environment, music choice, your ears, and also the amplifier. For personal listening in a small space and reasonably efficient speakers, (look at the dB per watt sound pressure ratings), you do not need a lot of power, and there are many excellent powered and passive speakers on the market. The HiFiBerry and IQaudio amps are good choices, or use their specs as benchmarks for selecting your system.
If you want something dirt cheap to prove the concept and not worry about trashing anything expensive, find some garage sale bookshelf speakers, and Parts Express B652 are often on sale for around $30 US/pair. [You get what you pay for - sound quality is good for the price, but not great vs. better speakers]. PE has an project to make these speakers self-powered using their DTA-2 amp (15W/channel) and a MP3 player box built into one of the speaker cabinets. I am thinking of trying something similar using Volumio, Pi, and one of the amplifier boards.
IQaudio do have a DAC specifically for a Pi ZERO - out of stock at present.
Phil