Here's my problem. Local bowling club have just installed and overhead projector and the audio is two phonos. The sound system is a Rediffusion RMA and RM2. The input to the RM2 is a 5 pin DIN. The pins are


1 - Sig I/P Unbalanced
2 - Sig Return
3&1 - Sig I/P Balanced
4&5 - Sel S/W


My idea for joining these two together would be to link the white and red wires from the phonos to pin 1 and the two black wires from the phonos to pin 3.

Is that correct?

No.

Since the Rediffusion system will be in mono, you need a mono signal to it. The best way is to join the cores of the L&R phonos together with 2 x 10K resistors in a Y-pattern. Connect the junction of the 2 resistors to the din input pin 1 then connect the screens of both L&R phono leads to pin 2. This will make your stereo output into a proper summed mono input and prevent any weird phasing effects (and possible mixer damage) caused by shorting the L&R outputs into one another.

If you have a mono switch on the back of your mixer, you can just switch that to mono then use either L or R (but not both) phono into the din socket as above, the resistors not being needed.

You may also need to fit a link between 4 & 5 inside the din plug to tell the amp that this input is to be treated as a priority input; it may work without but wont harm it to fit it in case. Some PA amps will ignore the input if this link is not fitted, some will simply mix it into the other channels but will fade the others down if this link is made. It's meant for a button on a tannoy microphone so that the music fades down and gives the mic priority if that's how the channel is internally configured. Dont forget to pull the DIN plug out complete at the end of the night or the owners may complain that the other channels have stopped working all of a sudden.

Just make sure the input you are using is a line input and not meant for a paging microphone level!

Thanks for that. The signal is coming from the Sky box and I've already changed the audio output to mono, so I'll be able to use just one lead, although I'll eventually join both as you've suggested. I'm trying to find out more info on the Rediffusion RMA, but I'm presuming that due to it's age, there nothing online about it. Would you happen to know what the current equivalent kit would be. I've looked online at 100v systems and there have different RMS outputs, which I vaguely remember is to do with the number of speakers in the chain, but can't exactly how to work this out.