Audio mute with led indicator--PCB Layout

[Cainester]

I'm trying to come up with a system to switch a balanced audio signal and an led indicator (on) at the same time. I'm swithcing 16 lines. The best I've come up with so far is a 3 pole switch. 2 poles get the audio and the other gets the led.
Is there a better solution?
Thanks,
Caine

 

[Rochey]

that sounds like the best idea.

they do similar things with FX pedals...

 

[[silent:arts]]

[quote author="Cainester"]Is there a better solution?[/quote]
Relays

 

[Svart]

you could do it with low noise JFETs if you want to do it sandstate.

 

[alk509]

Excuse me, but how exactly are relays or JFETs "better" than a straightforward 3PST switch??? Less is more, I say.

Peace,
Al.

 

[gyraf]

Relay contacts can be much more predictable over the long run than simple switches. Sealed and so on...

 

[bcarso]

If you can find them, mercury-wetted reed relays are very reliable. Inert-gas-filled regular reeds are almost as good if not abused.

Regular toggles are prone to adsorption of films on the contacts and consequent intermittency at low levels. They will drive you bonkers. They can be fine at first, then unruly things start to happen. If there is enough voltage in the circuit to zap through the films then you can be o.k., but low-level audio will not have that all the time.

Switches with some significant amount of wiping action can be pretty good---the old telephone-type leaf ones for example. But they are generally not sealed. So they are easier to clean but tend to get dirty faster.

Solid state will be reliable if not mistreated but will always have some limitations on signal swing, off isolation, distortion, etc.

 

[Cainester]

Thanks for the replies.
I like the reed switch idea. I googled mercury wetted reeds, and they are readily available. I was planning on mounting this stuff on a 2u rack blank for simplicity. How would the magnet actuator be mounted. Are there kits, or does one have to devise something.
In order to get the 3 poles, 3 reeds would be mounted side by side then a magnet big enough to cover all three would be used. Is that correct?
And then back to the magnet mounting dilemma

Caine

 

[stickjam]

Just use a DPST reed relay. You can then control it with something as simple as an SPST switch to switch the required voltage (usually 5, 12 or 24 depending on the relay) to the coil. Wire the LED and appropriate series limiting resistor across the coil.

 

[Cainester]

Ooohh,
reed RELAY- missed the relay part.
Thaks,
Caine

 

[bcarso]

One thing to keep in mind---if you use the Hg-wetted many of them are position sensitive---need to be oriented with respect to gravity so the little bit of Hg stays put.

 

[Svart]

something i thought of a while ago and have yet to try.. a slow ramping circuit to turn the muting JFET on slowly.. something you can't do with switches or relays.. have no idea if it would work but heck, give it a try.

a big name console maker($$L) uses JFETS as the active component in it's muting circuit.. I've seen it done many other times too. I don't see why people jump on the "gotta have the most expen$ive $witch or it's no good" bandwagon.. as Bcarso suggested, even the best contacts can degrade in performance for a variety of reasons. We reach too far into audiophool territory when we start *needing* contacts of certain materials and so forth too.. much like audio cables, at these levels and frequencies even a cheap switch/relay will do just fine as long as the contacts are clean and mated properly.

:thumb:

 

[Larry Sheehan]

Have a look at the ssm2402. The solo in my console uses one to switch the audio and the same transistor that toggles the switch inputs on that switches the LED.

 

[rlantis]

if you use the Hg-wetted

Get 'em while you can! It's looking as if it's just a matter of time before the manufacture and/or use of all components containing mercury will be banned.

BTW, the only allowed exceptions will be those applications deemed as being vitally important and without an alternative non-mercury solution.

For example, right now fluorescent lighting is considered essential and without any practical alternatives, but GE hopes to provide THE solution with their new Organic LED technology http://geglobalresearch.com/04_media/photos/20040304_oled.shtml

 

[cuelist]

[quote author="rlantis"]For example, right now fluorescent lighting is considered essential and without any practical alternatives, but GE hopes to provide THE solution with their new Organic LED technology http://geglobalresearch.com/04_media/photos/20040304_oled.shtml[/quote]

Good luck GE... OLED is currently at 15 lumens per watt. That's a 1/5th of the efficiency of todays fluorescent tubes.

 

[Svart]

they'll get it up to near Luxeon intensity sooner or later.. 5w=120 lumen. or 24 lumens per watt. fairly white too. everything is moving towards LED these days.

 

[Cainester]

I'm now getting to this project.
Gonna go the reed relay route. Trying to keep cost as low as possible. Will relays with these specs work:

Coil - 5V
Ohms - 500
Max Pickup - 3.8 V
Nom. power - 50 mW
Contact AC - 60V (max)
Contact AC amps - .25 (max)
Link to Relay

Is there something better?
Thanks,
Caine

 

[gar381]

Would 4016 cmos or DG308 chips be to dirty? Lots of desks in the '80s
used them for solo systems.

GARY

 

[Brian Roth]

Ahem


We do NOT live in a vacuum.

Relays with bifurcated contacts are a mainstay in the telecomm biz.

Bri

 

[Cainester]

Does anyone know of a bifurcated, or any low level relay that will fit into a socket?
I called mouser and none of theirs will. I'd rather not have to solder these into a pcb, so they can be changed easily if they fail.

Thanks,
Caine