3PDT switch wiring

[igore42]

Hello,

I'm currently building the rangemaster, (first build) and want to wire in a LED.  The instruction sheet doesn't show that variation so I looked around on the board and and saw the posting from Brian about the way he wires the 3PDT switch so that the input signal is grounded when in bypass mode.  I was wondering what the advantages of that wiring method are vs. the standard wiring on sites such as GEOFX, FuzzCentral etc?  How does the grounded input wiring effect the operation of the pedal vs the ungrounded input?  (BTW, the rangemaster is a positive ground pedal)

Thanks,

Doug

[madbean]

Doug,

The advantage of grounding the fx input in bypass is that it can help eliminate popping when the switch is toggled on and off. By grounding the input, you create a discharge path for any decoupling cap between the guitar signal and the circuit. Pulldown resistors also aid in this. But, not every effect out there has a pulldown, such as the RangeMaster.

It is not a must, but just an alternative. One which I've used successfully for several years, too! Not that at least one of the Tonepad diagrams has a grounded input set-up...although it is a little different than the one I show.

If using an LED in a positive ground effect, simply connect the negative terminal of the battery to a current limiting resistor. The other end of that resistor goes to the negative side of the LED (the flat side). The round side of the LED gets connected to the 3PDT switch in the same spot as a negative ground circuit.

[igore42]

Brian,

Thanks for the respose!  I did just wirer in a 3DPT switch with a LED on a pedal I had that was a 2PDT and it's not wired like you do, and guess what, it pops when it's switch!  (very annoying)  I thought I'd heard you can put in a "pull down" resistor to help that?  Which is more effective, the grounding method or the resistor method?  Seems like the resistor might color the tone?

Regards,

Doug

[madbean]

In this case I don't recommend a pulldown. Pulldown resistors can change the input impedance of a circuit. In the RangeMaster, that 68k acts to set the input impedance and this actually bleeds some treble to ground. That's a good thing because you are boosting the heck out of the high end frequency as you turn the knob up!

LEDs can also be a cause, themselves, of popping. I would try some variation of input grounding on your 3PDT, whether it's the one I show, or the Tonepad, or whatever. If you still get popping, try disconnecting the LED temporarily to see if it goes away.

[Bored]

I've seen many high-gain circuits cause noise when bypassed if the FX input isnt grounded.
The Fuzz Factory and Dr Boogie come to mind- if I used a mill bypass I would get oscillation when bypassed, but using a 3pdt and grounding the FX input cured the issue immediately.

Side question- If I ground the FX input do I still need the pulldown resistor? I do both,  but would rather not mess with the pulldown if its not required. 

[igore42]

Is the reason there is no LED or 9 volt adapter plug on the rangemaster because the original didn't have one or for other reasons?  Does the LED and or the adapter add additional noise?  If not using the adapter, would the LED drain the battery too quickly?