In article ,
Andy Luckman (AJL Electronics) wrote:

I want to provide mono (L+R) feeds into a helmet without stuffing the
amplifiers or affecting the loudspeaker output.

Well it looks like it will be 4 off resistors then. I have got a Starcom
intercom unit coming which has an isolated speaker takeoff point. I have
asked the manufacturers if the unit can be switched into mono, which will
make it easy.

Many thanks for all the suggestions. I really should have known the answer
myself, but old age fuddles the brain!

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AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk