Hello to all.
While doing true bypass on dunlop gcb-100 (bass wah) using 3pdt switch. After connecting all necessary wires there was one pole empty in switch, so i wired there +9v from battery. Now the battery is only connected when effect is on(and input jack is inserted) but it gives me a little pop when turning on. Tried the same thing with my fuzz face clone and it gives me pop again only when switching on.
The question: is it possible to turn off battery when bypassed and have no pop sound while starting effect(pull down resistors are present but don't work here)?
You'll most likely get a pop no matter what, You'll need more than a 1M pull down resistor to prevent the popping.
If it was easy to turn the battery on and off without any problems, you'd have seen it as standard wiring in true-bypass pedals for the last few years.
Most well-designed circuits that employ a shared power supply - whether batetry or external - employ an electrolytic capacitor of some moderate to semi-large value to "stabilize" the power, so that whatever one semiconduictor is attempting to do does not rob power or influence the power supplied to other semiconductors. The textbook case of this is LFO circuits that produce audible "ticking" in the audio path as a consequence of briefly "stealing" current to produce the square wave they need.
If that cap is of any reasonably high value, it takes a little while to charge up, before a 9v battery can deliver 9v to the rest of the circuit.
The upshot is that if the circuit has such a smoothing or "decoupling" cap, including it in the bypass function will mean there is a few moments - perhaps seconds - before the effect is fully powered up. This runs counter to the intended "punch-in/punch-out" function that people want from an effect pedal. I would imagine there are some cases where the slight delay does not matter, but there will be more where it does.
Quote from: Mark Hammer on August 23, 2010, 09:29:49 AM
Most well-designed circuits that employ a shared power supply - whether batetry or external - employ an electrolytic capacitor of some moderate to semi-large value to "stabilize" the power, so that whatever one semiconduictor is attempting to do does not rob power or influence the power supplied to other semiconductors. The textbook case of this is LFO circuits that produce audible "ticking" in the audio path as a consequence of briefly "stealing" current to produce the square wave they need.
If that cap is of any reasonably high value, it takes a little while to charge up, before a 9v battery can deliver 9v to the rest of the circuit.
The upshot is that if the circuit has such a smoothing or "decoupling" cap, including it in the bypass function will mean there is a few moments - perhaps seconds - before the effect is fully powered up. This runs counter to the intended "punch-in/punch-out" function that people want from an effect pedal. I would imagine there are some cases where the slight delay does not matter, but there will be more where it does.
so i should try putting capacitor (47~100uF) between circuit and battery
The cap goes between V+ and ground. The chances are good that whatever you are trying to build already incorporates such a capacitor.
My point is that because of that capacitor, you do not want to make the 3PDT cut the power supply when bypassing the effect, because when you reconnect the power, it won't come back on right away. And the reason it won't come back on right away is that very capacitor.
That is why, as anchovie noted, you generally won't see it as part of the switching arrangement in any pedals.
Also, if you use the true bypass scheme that grounds the board input in bypass, you shouldn't need pulldown resistors. I've wired two wahs this way, and neither needed the extra resistors. The diagram is shown on Fulltone's wah pages and many other places.
Al
Quote from: Mark Hammer on August 23, 2010, 11:01:12 AM
The cap goes between V+ and ground. The chances are good that whatever you are trying to build already incorporates such a capacitor.
My point is that because of that capacitor, you do not want to make the 3PDT cut the power supply when bypassing the effect, because when you reconnect the power, it won't come back on right away. And the reason it won't come back on right away is that very capacitor.
That is why, as anchovie noted, you generally won't see it as part of the switching arrangement in any pedals.
that capacitor between V+ and ground eliminates pop at turning effect off(when not present the pop is at power on and off)
Quote from: zombiwoof on August 23, 2010, 04:16:15 PMAlso, if you use the true bypass scheme that grounds the board input in bypass, you shouldn't need pulldown resistors. I've wired two wahs this way, and neither needed the extra resistors. The diagram is shown on Fulltone's wah pages and many other places.
Exactly what I did too based on Gaussmarkov's page here (http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b) on Wiring Up A 1590B:
Anyway, here's a schematic I whipped up in ExpressSCH detailing Gaussmarkov's 3PDT wiring:
(http://home.comcast.net/~snmavronis/3pdt_wiring_detail.jpg)
I hope this helps.
Quote from: Steve Mavronis on August 24, 2010, 12:51:05 PM
Quote from: zombiwoof on August 23, 2010, 04:16:15 PMAlso, if you use the true bypass scheme that grounds the board input in bypass, you shouldn't need pulldown resistors. I've wired two wahs this way, and neither needed the extra resistors. The diagram is shown on Fulltone's wah pages and many other places.
Exactly what I did too based on Gaussmarkov's page here (http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b) on Wiring Up A 1590B:
Anyway, here's a schematic I whipped up in ExpressSCH detailing Gaussmarkov's 3PDT wiring:
(http://home.comcast.net/~snmavronis/3pdt_wiring_detail.jpg)
I hope this helps.
thanks but my question/problem has other nature
lets say i did DPDT bypass wiring with input grounding and in third pole(from 3PDT switch) i disconnected +V from battery while bypassed and powering it gives me pop
anyway like it was written above it's not easy, maybe impossible to avoid that pop