user19892: So I tried to use one of those widely available solid-state relay boards to switch some 12V power, and I found out the hard way that they are not designed to switch DC current. They use some sort of variac that only works when AC voltage is applied. Do I have that right??
So I got this other project where I need to multiplex some audio signals in a mixer board, and I was already planning on using those solid-state relays before I learned all this. If I send audio through these relays, is it going to work as planned? Will I suffer any noticeable delay, signal degradation or attenuation?

user10794: A solid-state relay seems to be the totally wrong tool for the job. The image you posted shows it is intended to switch 240V AC. So it is designed to switch something like a 240V light on and off.
Relays in general are things designed to connect one thing to another (eg. power to a light). They just aren't designed to switch audio signals.

I need to multiplex some audio signals in a mixer board, and I was already planning on using those solid-state relays before I learned all this

The expression "when the only tool you have is a hammer, everything looks like a nail" springs to mind.
There are chips designed to multiplex analog signals (as I describe on this page). That would be closer to what you need.
However that chip (the 74HC4067) is a "choose one input from many" sort of design. It isn't going to let you fade one audio signal in or out (neither would the relay for that matter).

19892: <p>So I tried to use one of those widely available <a href="http://img.dxcdn.com/productimages/sku_384265_4.jpg" rel="nofollow noreferrer">solid-state relay boards</a> to switch some 12V power, and I found out the hard way that they are not designed to switch DC current. They use some sort of variac that only works when AC voltage is applied. Do I have that right??</p>

<p>So I got this other project where I need to multiplex some audio signals in a mixer board, and I was already planning on using those solid-state relays before I learned all this. If I send audio through these relays, is it going to work as planned? Will I suffer any noticeable delay, signal degradation or attenuation?</p>
 10794: <p>A solid-state relay seems to be the totally wrong tool for the job. The image you posted shows it is intended to switch 240V AC. So it is designed to switch something like a 240V light on and off.</p>

<p>Relays in general are things designed to connect one thing to another (eg. power to a light). They just aren't designed to switch audio signals.</p>

<blockquote>
  <p>I need to multiplex some audio signals in a mixer board, and I was already planning on using those solid-state relays before I learned all this</p>
</blockquote>

<p>The expression "when the only tool you have is a hammer, everything looks like a nail" springs to mind.</p>

<p>There are chips designed to multiplex analog signals (as I describe <a href="http://www.gammon.com.au/forum/?id=11976" rel="nofollow noreferrer">on this page</a>). That would be closer to what you need.</p>

<p>However that chip (the 74HC4067) is a "choose one input from many" sort of design. It isn't going to let you fade one audio signal in or out (neither would the relay for that matter).</p>
