Barry, will this get it done?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140149796100
How does that thing work? will it overlay the microphone input into the music output, thus using the same speakers, or will he have to dedicate, or at least put a switcher into some of the speakers for mic iinput.
It overlays the mics onto the music. You have volume controls for each mic and a master volume that will also effect the music. On mine there was a pass through so i was able to feed it to the amp. It is also an amp in it's own right if you want it to be. But i found running the speakers off it, it just wasn't that powerful enough hence i just passed it's output to the main amp.
The main issue is having some way of disabling the mics so people don't mess around with them when it's not karaoke. Your bes bet will probably be to run extension leads from that amp to sockets on the side of your juke (1 each side probably) then have a switch on each one that breaks the cable hence disabling the mics.
I don't know if i mentioned it but if you are using mics then a metal shower hose makes a great protective cover for the mic leads like what you get on the arcade cabs that have teathered guns.