Help with amp footswitch

[skullsplitter]

Totally noob here.

I built an amp footswitch and I wired it like this:



I tested it in a 30W Marshall solid state combo, it pops a little but it works. Before I try it in a 100w tube amp I wanna know if there is something I could do to improve it or any error I should be aware.

Thanks for any feedback!

P. S. I used a 3pdt because that's what I had available.

[PRR]

Welcome.

There's dozens of ways amp foot-switches work, depending on the amp.

That may work on the amp you tried it on.

On Old Fender, it would kill Reverb but the LED would never light. It might kill Trem, but there were at least two Ways Fender did this, and one my *not* like the LED+R in there.

[thermionix]

I agree with Paul of course, footswitches are only part of a circuit and how they work depends on the rest of the circuit.

Your diagram is essentially a SPST switch, which just makes or breaks a single connection.  Did the LED light up on the little Marshall you tried?  I don't see how it could.  The LED would need a voltage to light it up, and when you short that out it would probably be very bad for the circuit supplying that voltage.

What kind of 100W amp did you want to try it with?  Can you share a schematic?

[PRR]

> The LED would need a voltage to light it up, and when you short that out it would probably be very bad for the circuit supplying that voltage.

LEDs are useful, fun, profitable.

A number of recent-decades amps run some voltage through a resistor to the switch jack. When switch is closed, LED is off. When switch is open, LED is on. Back at the amp, the change of voltage 0V or 2V can be sensed and do something.

Do what? That's up to the designer.

Who can be very clever. Stacking LEDs and resistors can give multiple output levels from several switches on one wire. (My Honda gets three levels on one wire for audio and speed thumb-buttons.)

BTW: guitar-plug stuff "has" to be short-proof. It is far too easy to short a 1/4" plug. Also stage cables get stomped flat which shorts them. It is not wise to short things indiscriminately. I have seen some switch inputs where I thought the protection was dubious. But such goofs don't last long on the market; the next-year model will HAVE short-protection.

[skullsplitter]

I agree with Paul of course, footswitches are only part of a circuit and how they work depends on the rest of the circuit.

Your diagram is essentially a SPST switch, which just makes or breaks a single connection.  Did the LED light up on the little Marshall you tried?  I don't see how it could.  The LED would need a voltage to light it up, and when you short that out it would probably be very bad for the circuit supplying that voltage.

What kind of 100W amp did you want to try it with?  Can you share a schematic?

The led did light up but I think I have it reversed in the scheme I posted. The amp I'm planing on using it is a Laney GH100L. Amp Schematic

[PRR]

Here is the internal circuit for that amp's switching.

https://s25.postimg.org/xox9r3i8f/GH100_L_switch.gif

If you don't put a plug in, the jack shorts itself; a panel switch breaks the connection so you still have a choice.

Plug can be open, short, or LED. Max jack voltage is 4V; max jack current is 4.5mA. Safe to touch, safe for LEDs.

Shorted, the jack voltage is near zero, TS2 is off, and I hope I have worked-out the rest of the convoluted logic.

Jack not shorted, voltage rises to something over 0.7V, the ON voltage of TS2. It may go to the 2V-3V of an LED in the pedal, or to the 4V of D2, doesn't matter.

[PRR]

Can you guys see this image?

https://photos.google.com/photo/AF1QipPf6ejo1Yd_iFuJdHuAmXWu65eijNum4pvSmSSY

(if so) Lower Right is the simplified switching for some old amp. Same idea: voltage through a resistance so an LED can be lit, or shorted; 0.7V threshold of actual switching allows a 2V-4V LED to be powered. 10K protects the internal switching transistor. Here it just makes/breaks power to a trem oscillator, but you can switch ANYthing with basic logic techniques.

[bluebunny]

Can you guys see this image?

404, Paul. 

[duck_arse]

Can you guys see this image?

https://photos.google.com/photo/AF1QipPf6ejo1Yd_iFuJdHuAmXWu65eijNum4pvSmSSY

"update your browser". as usual, mine is not listed.

[PRR]

I suspect a permissions issue on my end. Try this:

http://oi67.tinypic.com/r1g0uh.jpg

[duck_arse]

"I see everything twice". tinypic and postimg are the same, and visible.