Car audio Line-in input selector.

[argoaudio]

Hi all

First post in this excellent forum.

I need to select between 2 line-in inputs to my car's stereo system. Via our local RS-Components store I can source the SSM2404 which I have seen mentioned on occasion in this forum. I love the idea of "pop-less" switching.

My struggle is understanding the best way of implementing this IC for car use? Its a single supply IC (and dual) down to +12V and up to +24V. So the questions are:

a) A car's electrical system is around ~+14V when running. Would a variable V+ affect performance at all? Shoud I regulate V+? Problem with regulation is there is liitle V+ headroom for a reg to operate in (given 2204 Min V+ = 12V).

b) Using a single-rail supply should I 'float' the input/output around +6V (0.5 x V+) via a RC network? If so, what values for car audio (not that car audio is any different than standard 'hifi' audio)?

d) Should I bother with and snubbing/filtering on V+ given its on a vehicle supply?

Or should I give up on solid-state switching for a car and just use relays. If so any tricks for stopping 'pops' during switching?

Many thanks!

[Perry Babin]

When using relays, many people leave the unconnected source outputs unloaded which allows DC to leak through and charge the output side of the DC blocking capacitors in the signal line. Connecting a 100k ohm resistor from the center conductor to the shield of all components will generally eliminate the popping.