3PDT LED pop when switching

[spargo]

I have built the AMZ MOSFET booster with true bypass.  When I switch the effect ON (off is fine), there is a pop.  I've determined this to be the LED, since if I remove the LED there is no pop.  I've tried the following: http://www.muzique.com/lab/led.htm but to no avail, with caps all the way up to 47uF.  I'm using a superbright green LED.

The LED is 9V > resistor > LED > switch which is then grounded when switched on.

Any ideas?

[SpufuZ]

Have you tried an other LED?

[rpjones]

I had the same problem with mine, tried the AMZ fix with the cap and resistor on the led, still no good, I finally solved the problem by wiring the 3PDT like this:

http://www.tonepad.com/getFile.asp?id=76

use the diagram for offboard wiring number 5, you should be good

[spargo]

My switch is wired differently than that but I think it ends up being the same with input grounded.  Is this the same?

Switch lugs, as if you are looking at it from above:
1 2 3
4 5 6
7 8 9

1 > board input and jumper to 8
4 > jack input
7 > jumper to 9
2 > ground
5 > LED negative leg
3 > board output
6 > jack output

In this configuration the input is grounded when switched off.  Isn't it just a nicer way to organize number 5 in that diagram?

[.Mike]

I think I drew this right according to your description...



If this is how it is wired then no, the input is not grounded when bypassed. The input is connected to the LED when bypassed.

A couple of things worth noting:

- The Mosfet Booster schematic has no pull-down resistor at the input, nor does it have a volume control to act as a pull-down resistor at the output. I don't know if it needs either, but these are typical solutions for reducing popping.

- If you pull too much current for your LED, it can induce popping. What type of LED and what value resistor are you using for your LED?

Mike

[Steve Mavronis]

Thats it - very similar wiring as from Gaussmarkov's article (http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b) on wiring a 1590B. I made a schematic version a while back for my pedal project too:

[.Mike]

Thats it...

Actually, it's not. I drew that little drawing based on Spargo's description to show that it is incorrect, and not grounding the input when bypassed.

That drawing does not match either the drawing you linked to, or the schematic you posted.

Mike

[Steve Mavronis]

Thanks for correcting that. I meant it was similar except I forgot to note that the only difference that switch lug B2 should go to the output jack sleeve ground vs the battery negative in his wiring. In the one I referenced the PCB input does get grounded when switched to bypass. Worked well for me with no issues at all. He could easily modify his current switch wiring to this method if he'd like to.

[alex192]

If it helps, I have just solved the problem why the LED pop fix doesnt work with the AMZ link -- the ground coming off the capacitor should be attached to the footswitch on the same lug where the led connects, and not a chassis ground point.

[Mark Hammer]

Is it possible to reduce the current draw of the LED by increasing the value of the current-limiting resistor, or are you presently at the limits of what provides sufficiently visible status indication?

Consider use of approaches that might increase the visibility of the LED, such as black plastic bezels that provide maximum visual contrast at much lower illumination.  If you can see the LED clearly with a 10-12k resistor in there, that can go a long way toward de-popping the pedal.

[Philippe]

Is it possible to reduce the current draw of the LED by increasing the value of the current-limiting resistor, or are you presently at the limits of what provides sufficiently visible status indication?.....If you can see the LED clearly with a 10-12k resistor in there, that can go a long way toward de-popping the pedal.

This approach is perhaps the best remedy (as well as an identical solution to the other thread about the 'popping' A/B box.)

If you are using those 'ultra-bright' LEDs, the higher ohm resistor will probably curtail the pop while leaving substantial illuminated visability.

[spargo]

Heh, well, that's the thing.  I do have superbright LEDs and I do want them at max brightness.    I use 270ohm resistors on them.

And Mike is correct, I connected my switch wrong so the input was not grounded when bypassed!  I'm not sure if this solves the problem, I haven't had the time to test it yet.  I will probably try it out tomorrow and let you know.

[spargo]

Hey guys, got it figured out with the MOSFET booster.  Once I had the input correctly grounded in bypass, no pop!  And I'm even using a full-current superbright green LED with a 270ohm resistor, and no need for any pulldown resistors.  Thanks to .Mike for pointing out my mistake!