True Bypass Wiring - Am I Overthinking This?

[bortlett]

I'm building a Tremulus Lune right now. I'm OK with getting the circuit to work, but I am trying to set up the true bypass wiring, and think I may be overthinking things (or maybe I'm just picky about the bypass wiring).

The schematic for the circuit is here (sorry for links instead of pics, here): http://commonsound.org/tremulus/tremulusscheme.pdf

I have no problem actually wiring the true bypass as suggested on their wiring diagram (http://www.commonsound.com/tremulus/pcb2.4.1/wiring.pdf), but I don't necessarily like that setup. I've used something similar in the past, and have noticed that some circuits tend to leak into the bypassed signal because the input of the board is not grounded when the bypass mode.

I typically use a setup like this:


My issue is that LED1 (it blinks with the rate) in the schematic doesn't connect directly to ground, so if I added that extra jumper between the board input lug and the empty lug on the common sound wiring diagram, the bypass mode would connect the input of the board to R11, pins 1/2 of the 4558, and the depth pot instead of ground. To me, that seems like a bad idea since I'd be mixing the bypassed audio signal with the LFO (this could potentially lead to even more leaking?)

My solution is to use a 4PDT. I would wire 3 of the poles just like the common sound wiring diagram suggests, then add this for the 4th pole:
--Empty (maybe add another LED for on/off just because the extra lug is there and I like LEDs)
--Ground
--Jumper to the board input lug

I drew a crappy pic to maybe help explain my solution (the additional pole is 2nd from the left):

Bypass by bort_lett, on Flickr

I know there are a ton of ways to wire true bypass, so I'm sure there are multiple solutions, but my main question is:
Is there a way to achieve my goal of grounding the board input in bypass mode using a 3PDT instead of a 4PDT (without just taking the rate LED out of the switch and letting it blink all day long)?

I'm building this on perfboard, so I have plenty of space/flexibility to make changes to the circuit if necessary.

[multi_s]

My issue is that LED1 (it blinks with the rate) in the schematic doesn't connect directly to ground, so if I added that extra jumper between the board input lug and the empty lug on the common sound wiring diagram, the bypass mode would connect the input of the board to R11, pins 1/2 of the 4558, and the depth pot instead of ground. To me, that seems like a bad idea since I'd be mixing the bypassed audio signal with the LFO (this could potentially lead to even more leaking?)

you could leave hardwired the LED Anode to pins 1,2 of the 4558. Instead but a break inbetween r12 and ground. make the switch connect r12 to ground instead of the LED, it should have the effect of turning on or off the led. use 3pdt as normal. i think EatYourGuitar knows more about 3pdt switching layouts which ground inputs/outputs when bypassed so maybe he will chime in. ITts liek you said, there are amny solutions to the wiring.

also what do you mean by 'leaking''?

[bortlett]

Thanks for the suggestion. That idea had crossed my mind, but I was having trouble wrapping my brain around it. It actually makes a ton of sense now that you wrote it out. I still have the LFO on my breadboard, so it should be easy enough to test tonight.

I couldn't figure out a better word to use than 'leaking.' What I meant was using a layout that doesn't ground the input wire, I had a distortion pedal that you could clearly hear the whine/hiss of a distorted signal even though the circuit was being bypassed. The gain had to be cranked for it to be noticable, but the noise wasn't subtle with everything dimed. Adding that jumper to ground the input wire fixed the problem instantly. I have also run into it on a TB looper, and when I had a phaser on in the loop, I could occasionally hear wooshing even when the loop was bypassed. This was far more sublte than the distortion pedal. Again, adding that jumper fixed the problem. My concern is that the LFO in the Tremulus Lune could potentially cause a similar problem, and I'd hear some sort of wobbling even in bypass.

[multi_s]

hmm ya if you are worried about the LFO generating noise maybe you could find a way to actually have the stomp disable it instead of just disconnecting the LED.

[mysteriousj]

Use two LEDs one for bypass the other for rate?? You'd have to fix the LFO to always on by shorting out where the 3pdt switches it off and wire the 3pdt exactly how you'd normally do it. That way you can see the rate even when you're bypassed which can be handy.

[eatyourguitar]

i think EatYourGuitar knows more about 3pdt switching layouts which ground inputs/outputs when bypassed so maybe he will chime in.

oh you knew this was coming

I do this on every pedal. grounded input, grounded output. nothing gets through! the wah version of the parallel universe leaked through on bypass but thats only because the oscillator is a speaker amplifier cranked up to 11 running through an unshielded snake in a wah enclosure at audio rates.

hmm ya if you are worried about the LFO generating noise maybe you could find a way to actually have the stomp disable it instead of just disconnecting the LED

unless you can generate magnetic fields big enough to bend spoons at low frequencies, I think a grounded effect out has you pretty much covered. 4558 outputs about 1ma.

[bortlett]

Ooh I like that. Thanks!

[bortlett]

you could leave hardwired the LED Anode to pins 1,2 of the 4558. Instead but a break inbetween r12 and ground.

I do this on every pedal. grounded input, grounded output. nothing gets through!

I used both of these suggestions, and it works great. Thanks!