From: whit@carson.u.washington.edu (John Whitmore) Subject: Re: Suggestions on Audio relays ??? Organization: University of Washington, Seattle Lines: 20 NNTP-Posting-Host: carson.u.washington.edu In article billq@ms.uky.edu (Billy Quinn) writes: >I built a little project using the radio shack 5vdc relays to switch >audio. I got pretty bad 'clicks' when the thing switched. > Is there a good relay/relay circuit that I can use for switching >audio, so that there will be *NO* noise of any kind on the audio lines. With relays alone, you will always get a transient when you abruptly turn ON or OFF any channel. If you don't want to hear the transient, use some other device (a photoresistor-output optoisolator is the usual sort of thing) to gently MUTE the signal, then switch, THEN remove the power from the lamp in the optoisolator. It used to be standard practice to employ photoresistors in switching audio, because the photoresistor time delay (a few thousandths of a second) kept any noise in the digital side (which drives the lamp) from contaminating the audio. And, the devices are cheaper than relays. John Whitmore