I've recently bought a Raspberry Pi to use as an AirPlay device, using Shairplay. However, I've realized that the audio quality from the 3.5 mm plug on the Raspberry Pi is quite bad, meaning that I'm thinking about investing in an extra output board with better outputs.
I've been looking at the products from HiFiBerry, and they offer both analog and digital solutions. I would like to invest in a board with an optical output, but I'm a bit unsure whether this will restrict me from adjusting the volume of what I play from my phone as I can do when using the standard 3.5 mm plug on the Raspberry Pi itself. I guess that I can't do this, since from what I've understood, optical output signals don't carry any volume information.