Mute switch/killswitch with LED - Prevent Popping

[daleykd]

Hey gurus!

I'm trying to build a super simple mute switch in a 1590A enclosure.  I've got the muting part to work great.  However, when I put in an LED using a 3V CR2032 (I'm doing this because a 9V won't fit in my 1590A), I get a nasty pop when switching to mute.  I followed this schematic: http://www.diystompboxes.com/smfforum/index.php?topic=63654.msg502198#msg502198, except I have no limiting resistor since it's a 3V.

Is there anything simple/inexpensive that can be done to eliminate the pop?  I was hoping to not using a 3PDT, since I have quite a few DPDT lying around.  But if a 3PDT would fix it, I'll do it.  I'd be happy to use a cap or resistor, too, if that would work.

Thanks in advance,
Kyle

[daleykd]

Would Jack Orman's LED popping article (http://www.muzique.com/lab/led.htm) be the solution?

[PRR]

Take the battery out, be sure it isn't some other source of pop.

Use a LED limiting resistor EVERY time! Even if only 100 ohms. If a Red LED, you should probably be using 470 Ohms.

[daleykd]

Good to know about always using a resistor, even if only 3V.  I will try to take the battery out later today and see what happens.  I didn't have a pop until I put the LED circuit in. 

I tried Jack's circuit, with his exact values, and the pop still happened.  (Of course, the LED was so dim, you could barely tell it was on.  :-) )

[R.G.]

I think we have a new flush of recruits from the sudden flurry of "why does it pop" questions.

The bottom line to all of these is that if it pops, the switch action is causing a sudden change in the voltage level when it makes contact. The sudden change in level can come from several different causes. Caps left open by switching is one, and this is solved by pulldown, or pull up resistors to keep the same DC on the cap when one end is open. It can come from a sudden power supply or ground shift when the current changed by the switch gets back into the circuitry and is amplified into a pop. And it can even be radiated or capacitively coupled from some switched part of the circuit to a sensitive high impedance node. These all have different fixes, and unfortunately, you have to go learn why they happen to fix them.