alistermorton

I'll give rapid a go if you want.

The TCA0372 does seem to be fairly uncommon. Neither Rapid nor CPC list it, and Farnell only have the 8 pin dip in stock. EDIT Belay that - the 8 pin dip is the one we want, isn't it?

Looks like they're easily available as spares e.g. http://www.ebay.co.uk/itm/10-x-STEEL-STRONG-METAL-BELT-CLIP-UTILITY-SPRING-CLIP-MONEY-CLIP-MULTI-USES-/251283766330

Yes, I noticed that and thought it meant it was switch selectable i.e. high gain, no bias voltage for dynamic or lower gain and bias voltage for condensor. Brian and Boatman can no doubt clarify. Continuously variable would be nice if it wasn't a problem. The Canford cans we were using looked remarkably like Stonewood ones, AIH.

This all sounds terrific. Can I make a couple of late suggestions? Could the mic gain be adjustable, even if, like is common for side tone rejection, it is via a trimmer. Last week we were at Minack where they had a mix of canford cans and ASL cans and the mic levels seemed to be quite different. Instead of a "siren", a vibrator as found in mobile phones might be a better alternative. However, as he design stands , it still sounds excellent, and you are to be congratulated and thanked for such a fine effort.

Yeah, but where's the fun in that ;-)