Clicking/popping from footswitch audible on my new hybrid amp project, ideas?

[mlove3]

The channel switch circuit is a latching footswitch, voltage divider input to a max 314 switch IC which controls a relay. It all works but I can hear the pop not just when I engage the f/s, but I can also hear the click coming through the amp when I take my foot off the footswitch ,after it's already latched and the channel is switched. So the mechanical release to rest position creates a click and the click is amplified. Is the preamp so microphonic that it's actually picking it up? I shunted a .01 cap across the switch, that didn't do it.
Anyone?

[Enzo]

Wire up a toggle switch on the end of a wire and flip that. ANy difference?

Your stomp switch may be a latching type, but that doesn't meran it doesn't have a little contact bounce as you release the switch.

[mlove3]

Wire up a toggle switch on the end of a wire and flip that. ANy difference?

Your stomp switch may be a latching type, but that doesn't meran it doesn't have a little contact bounce as you release the switch.

good idea. Or I can short it at the connector, the chassis is open. The switch definitetly bounces, the question is why am I hearing it through the amp? The f/s connector is at the opposite end of the pre.

[Jazz P Bass]

What you are trying to ascertain is whether or not the switch contacts themselves are 'bouncing'.
If they are, it is a mechanical/ electrical signal being fed through to the connector.
The 'bouncing' contacts make a spurious signal.
An RC circuit could snub that out.

[mlove3]

What you are trying to ascertain is whether or not the switch contacts themselves are 'bouncing'.
If they are, it is a mechanical/ electrical signal being fed through to the connector.
The 'bouncing' contacts make a spurious signal.
An RC circuit could snub that out.

Yeah, tried a quick and dirty RC with a .02 and a decade box, I'll experiment a bit more this weekend. I'm just surprised that much bounce is coming through.

[Enzo]

There is contact bounce in the electrical sense, which happens on a microscopic scale, and for things like logic circuits which act instantly it can confuse them. I did not intend that. All switches bounce in that sense.

I had something mechanical in mind. You press the switch, the contacts switch over, then as you release the switch, for some reason your contacts have a brief open as the mechanism goes by. That of course momentarily affects the circuit as well. If switching with a toggle or shorting the wires together eliminates the symptom, then you have a defective stomp switch. I wouldn;t be trying to solve it with caps and resistors.

WHy are you hearing it through the amp? The switch is opening and closing when not desired. Does it matter how far away it sits? It is turning your channel selection off and one for an instant. That is what you are hearing, not some radiated spark. And even if it was a spark, it is WIRED directly to the amp, it matters not how many feet of wire there is between them.


here is a different way to think of what I am saying. Switches come in two types: make before break, and break before make. The first ones are also called shorting types, because for a moment, both sides are connected together. I am suggesting that for some mechanical reason, your switch has a bit of a make before break action. The switch contacts transfer over as you stomp, but something has a little friction and briefly drags the contacts away from position on the way by as it returns to rest.

[mlove3]

WHy are you hearing it through the amp? The switch is opening and closing when not desired. Does it matter how far away it sits? It is turning your channel selection off and one for an instant. That is what you are hearing, not some radiated spark. And even if it was a spark, it is WIRED directly to the amp, it matters not how many feet of wire there is between them.

I understand. Let me clarify a couple of things tonight, I have two footswitches that I can try, I beleive they both give me the same problem, so that would rule out a bad switch.
If I forgot to mention this a latching footswitch, not momentary. So again, to clarify, I press the switch and leave my foot on the switch, the channel changes. When I lift my foot off the switch I hear the boingy mechanical bounce of the switch through the amp. I don't get this problem on my gigging homebrew...or do I? Maybe I never noticed!

I'll try it tonight!

[loudthud]

I think you need to look at the circuit you are switching. Are there any capacitors blocking DC where one side of the cap goes to the switch with no resistor to ground? Circuits like that will give a click or thump when you through the switch.

[mlove3]

I think you need to look at the circuit you are switching. Are there any capacitors blocking DC where one side of the cap goes to the switch with no resistor to ground? Circuits like that will give a click or thump when you through the switch.

no.

[Enzo]

Am I right here? The amp does this with your stomp switch, but does not do this when shorting across a plug or putting some other switch at the end of the wire? If that is the case, the only difference between them is the switch.

You did mention is is a latching switch. Any reference I may have made to momentary meant something touching briefly, not the action type of the switch.

And feel free at any time to post the schematic of your switching circuit.

[mlove3]

Am I right here? The amp does this with your stomp switch, but does not do this when shorting across a plug or putting some other switch at the end of the wire? If that is the case, the only difference between them is the switch.

You did mention is is a latching switch. Any reference I may have made to momentary meant something touching briefly, not the action type of the switch.

And feel free at any time to post the schematic of your switching circuit.

It's definitely the switch noise coming through the amp. The question is how do I get rid of it? The RC shunt is a good idea, I'll experiment more with that.

[Enzo]

Just for science, with the switch in the open setting, whip the cord against the floor. Does that make a noise? SOmetimes coax can get microphonic.

[mlove3]

Just for science, with the switch in the open setting, whip the cord against the floor. Does that make a noise? SOmetimes coax can get microphonic.

ah, great idea, I'll try that tonight. Last night I tried more RC shunt combinations, nothing worked to diminish it. I also am going to try moving the wire that connects to the switching circuit, it runs along the chassis away from signal but could still be a problem. I listened closely on my gigging amp, it has the same switching system, it did NOT have the same symptom.I attached the switching circuit schematic, the IC is a maxim 313 analog switch.As I said, I use the identical switching circuit on my big boy with no problems over many gigs.

[loudthud]

That MAX313 can switch pretty fast which means you really need to de-bounce the control signal. With a 1.2K pullup, something like 10uF should be tried.

[mlove3]

That MAX313 can switch pretty fast which means you really need to de-bounce the control signal. With a 1.2K pullup, something like 10uF should be tried.

Worth a shot, I'll try it later.