I do a lot of one-shot shows with same-day load-in so normally I just use the mini-plug out of one of my playback laptops to play music or sound cues necessary. I’ll either go into the ST 3 or use a mini-to-dual 1/4″ adapter into one of the stereo channels or even channels 15/16 linked together (so I can have quick access to their faders while on the top layer).
The issues Andreas brought up about noise induced by computer power supplies was something that I had experienced consistently many years ago but nowadays I have almost never experienced this same noise issue. I think that computer power supplies and integrated sound cards have improved dramatically, to the point where I never think twice about connecting a computer via mini jack to my console. To be prepared for a problem on a job I do carry a Rolls Buzz Off, which is a small, inexpensive transformer box that does a perfect job of cleaning up any power-induced noise. I’ve not had to use it for a while but I still carry it all the same.
I experience it every week at church – the laptop has to be running on battery – it can’t be a ground loop because it’s double insulated – it’s a PSU hiss…