The amplifier is already installed. Essentially its for a science display = unit, where a single audio signal is sent to this multi-channel amplifier. = Sensors pick up when the person is walking along, so rather than blasting = out audio all along the walkway, it "follows" the user, switching it from o= ne speaker to the next. = Yes..there are issues. The exhibit is designed so that the viewer will b= e single or at least grouped together so no worries about having to turn on= the speaker 3 stations behind..etc. The other issue, and the client is aw= are, is the possible "popping" of the speakers when they are turned on and = off. But he will live with that. = So, relays it is. And yes there is of course, a PIC driving the relays a= nd watching the sensors. Michael Rigby-Jones wrote: = >-----Original Message----- >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] = >Sent: 09 May 2006 00:53 >To: Microcontroller discussion list - Public. >Subject: Re: [EE] switching audio signals 50W > > >alan smith wrote: >> 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. >> = >> 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. >> = >> = >> --------------------------------- >> Talk is cheap. Use Yahoo! Messenger to make PC-to-Phone = >calls. Great = >> rates starting at 1=A2/min. > >Considering the cost of decent relays and the low cost of audio amp = >chips I would use a power chip per channel. If you only drive one at a = >time your power supply is still small. That's ok, but not so good if the OP wants several different amp outputs to= be switched to a common speaker. I can't think of anything more suitable than relays for this, any solid sta= te switching scheme is going to end up far more complex. Regards Mike =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist = --------------------------------- New Yahoo! Messenger with Voice. Call regular phones from your PC and save = big. -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist