Steve Smith wrote:
> Relays probably the best. Look at the current in a 4 ohm speaker to generate
> 50 w it in the order of 3-4A this has to be switched without adding
> distortion so the on resistance of the switch ie critical. Check out
> amplifiers that have an anti thump relay (never an anti thump fet switch).
> Relays are also available double pole for more than one channel in a single
> switching device!

So you're saying that a low Rds(on) FET (or pair [N&P]) won't work well enough?
I don't see why not, given that cable resistances are an order or two
of magnitude larger. e.g.
http://www.irf.com/product-info/datasheets/data/irf7459.pdf
9 milliohms at 12A and 20V rating in SO8 package.
You just have to be sure the device is hard on as the output gets
near the supply rails.


> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
> alan smith
> Sent: 08 May 2006 04:22
> To: Microcontroller discussion list - Public.
> Subject: [EE] switching audio signals 50W
> 
> OK audio guys.....
>    
>   I have an amplifier that can deliver up to 50W of audio per channel, and
> need to switch on and off differnent channels outputs depending on some
> control inputs.  I was thinking of relays but that rather a large real
> estate usage, so wondering about just using some of those small solid state
> photoMOS relays, like those used in telco applications.

Too much resistance from what I could see,(3 ohms or so) and
no where near the needed current (0.5A or so).


>   Its a one-off project, so production costs aren't of a real issue other
> than I do want to keep costs down of course.
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