amp footswitches

Post by **Mike** » Tue Dec 01, 2009 9:47 pm

Yeah that's what I thought, which means the diode type is crucial. The wrong ones wouldn't work it seems.

Progrockabuse · Post by **Progrockabuse** » Tue Dec 01, 2009 11:59 pm

i'm i thinking this may be a lost cause?

did think about just building the existing board into a smaller case. might just go in an MXR style box.

or could i replace the momentary channel stomp footswitch with a momentary toggle switch on flying leads?

Post by **dots** » Wed Dec 02, 2009 12:02 am

rehouse the circuit board in a box with only one switch?

Bill Oakley · Post by **Bill Oakley** » Wed Dec 02, 2009 12:06 am

Why do you think this is a lost cause? It's seems with all this information given to you, it would be very simple. I even included a DIY illustration for both switches. You just have to wire up the reverb switch in whatever box you want.

Remove the Reverb switch from the board, solder an LED and a diode like in the illustration I provided and attach the wires where the illustration says to. Doesn't get too much easier than that. You can even use the LED and diode from the original switch. I would.

Progrockabuse · Post by **Progrockabuse** » Wed Dec 02, 2009 12:09 am

mainly as i'm an electronics noob. don't want to fuck it up. plus i'm thinking to clone my original footswitch, so if i ever sell the amp i can sell it with the original switch.

Bill Oakley · Post by **Bill Oakley** » Wed Dec 02, 2009 4:22 am

Well then you need to get an enclosure, a momentary stomp switch (I assume it doesn't latch), a 1N4448 diode, a LED, some cable, a switching jack and 2 stereo 1/4 plugs.

Post by **Mike** » Wed Dec 02, 2009 9:17 am

Bill Oakley wrote:a 1N4448 diode

That's the pertinent information I was missing. Sorry, I'm rammed busy at work and Stress is literally leaking out of my eyeballs. I didn't have time to properly peruse the schematic.

If I was you Rob I would just keep your normal footswitch.

Post by **Mike** » Wed Dec 02, 2009 9:18 am

Bill Oakley wrote:a momentary stomp switch (I assume it doesn't latch)

I would assume it does latch or how is the LED going to stay on?

NickS · Post by **NickS** » Wed Dec 02, 2009 9:47 am

Mike wrote:Wow. Cheers for all the info. Looks like it doesn't act like a normal "ground the tip or the ring to the sleeve" pedal at all, but that the amp is sensing the LEDs that are on via the tip connection.

Yeah, p[retty much. Take the lower schematic. There's 30 volts AC going to the footswitch, R132 providing current limiting and being the top of a divider R132/R133?R134/R140. If you close the Channel Select switch, the positive-going half of the AC is clamped to the forward drop of the diode and LED. If you close the the Reverb switch, the negative-going half of the waveform is clamped to minus the same drop.

Take Channel Select: Back in the amp the waveform is fed by a divider R133/R134/R140 to D165. When the Channel Select switch is open, the positive-going half of the waveform is large enough to be rectified by D165 into C115 and exceed the 2-diode drop on the other input of the comparator. When the switch is closed the positive-going half of the waveform isn't large enough so the comparator output goes the other way.

Reverb is slightly more complicated as it uses a charge pump to generate a positive input on the comparator from the negative input waveform.

In both cases, I would assume you need a latching switch; the voltage levels on the schematic ("OFF +1.6VDC, ON +.25VDC") don't indicate any flip-flop action.

Hope that helps.

Pens · Post by **Pens** » Wed Dec 02, 2009 10:10 am

NickS wrote: In both cases, I would assume you need a latching switch; the voltage levels on the schematic ("OFF +1.6VDC, ON +.25VDC") don't indicate any flip-flop action.

Oh, yeah this is probably true. Didn't think of that.

It's so fucking nice to have other electronics guys here now to brainstorm this type of shit.

Post by **Mike** » Wed Dec 02, 2009 10:32 am

In NickS's case there it was less brainstorming and more SCIENCE DROP

Pens · Post by **Pens** » Wed Dec 02, 2009 10:41 am

Pretty much. What I mean is I have less and less time to devote to thinking about schematics and such, and you have been so busy as well, it's awesome to have others around that know their shit to actually take the time to drop science.

This board is head and shoulders above the rest.