I've had an idea for an electronics project I'd like to start on. The story is that I work as the ICT tech in a school. I often help out in assemblies when a teacher wants to use multimedia. When audio is involved I like to fade the sound out rather than just pause the video the sound is coming from. I often can't do that so I thought a sound volume control slider would be a cool thing to design and implement. It'd sit next to the laptop and take a 3.5mm connector to take in audio from the laptop. I'd then have a slider or a dial to allow me to fade in and out sound so it sounds a bit more professional.
The volume controller would have a 3.5mm connector to allow me to connect the sound cable that runs to the amp feeding the speakers in the school hall. Some of you might ask why I don't control the volume from the amp; well because of where the projector has to be the amp is several metres behind me so I can't be at both the laptop and amp at the same time to pause videos and fade sounds out.
I've had a look on a shop's online site and found 3.5mm sockets that I could use. I just need some help with how to get a slider or dial to control the volume. I'll also need to make up some kind of case for this.
So any ideas how I could make one? I've seen sound mixers but they are all £30+ and don't look that good, beside it'd be fun making my own one.