I decided I needed a banana-to-minijack converter box so I bought a cheap cast aluminium enclosure from Ebay and set about it with a centre-punch, step-drill and several coats of enamel paint!
Standard fare really: 12 banana sockets <-> 12 minijack sockets with a common ground output. Works like a charm.
I did, however, discover a few things about spray painting:
1) I'm hopeless at it! I think this is mainly because I seem to lack the patience to follow the most basic instructions like 'Spray several light coats or the paint will run if applied too thickly'
2) When it says on the tin 'Only use when temperature is over 10 degrees C' - this is not a suggestion. Did the first couple of coats and then forgot that I'd left it in the shed overnight. Cue -3 degrees overnight temperature. Cue paint all cracked and flaked in the morning. I had to scrape/sand it all off and start again.
3) When it says 'Touch dry in 10 minutes', it means touch dry! Hold it too tightly while you're screwing in banana sockets and you'll be left with lots of 'interesting' fingerprints set into the paint surface!
Always learning, always learning...