Hey folks. I've made a circuit that has an output of digital high or low, and I want it to open and close a switch that audio will pass through. I've tried a few different circuits for the switch but all of them have some "pop" to them. The digital may switch pretty quickly, 5-10 Hz. I've tried usual stuff like adding caps to ground on output, putting cap Vcc to GND. Tried a 4066 analog switch and a JFET switch.

Sounds like you need an analog switch that ramps up rather than just simply snapping on and off. It can be done with a voltage follower circuit where the signal can come up from a ground state to its full output state smoothly.

I'll see what I can come up with and get a sketch posted shortly.

Ok, cool Mongo. Could be like a VCA? Or a cap charging up to modulate a programmable op-amp?

Similar. I haven't had much time to think on it but essentially, it's a simple circuit that just brings up the supply and gain between two circuits. They can be parallel circuits and switched in and out to a common output or separate outputs. I'll try to get some time later tonight.

May be this could help.

-Raja

Raja, Great set there. Yeah, something like that. I was thinking along the lines of NPN transistors but FET's work niicely too.

I constructed the second circuit on that page (thanks Raja) a few days ago and I still get some popping...confused.

The schematics will all probably give a little pop while switching.

The circuit that uses the 4016 chip would be the best but one minor alteration might help.

On the gate input to the segment, add a 1M resistor in front of it and at the input, add a small capacitor to give a slight delay in the signal so it gently goes online instead of abruptly.

Gate??? I don't see a FET in the 4016 circuits. Which schematic?

The "gate" on a 4016 is the control input. Pins 5,6,12 and 13

Ok, cool I'll try it...I don't have a 4016 lying around but I'll buy one on Monday. So 1M from pin 13 to the node below it? Thanks...will report on it.

Thanks for your help, I appreciate it, but I need to know which of the multiple schematics on that page that you are referring to when you speak of adding components to a gate :)

I would recommend using a BJT for this, which eliminates a physical disconnect- and is an analog component itself. Beyond that, if you have an issue, consider adding a filter circuit.

BM

It has been a while so I will have to review the thread to see where it left off.