Pedals that don't need true bypass

[rockgardenlove]

So, I have an SPDT switch.  What kind of pedal might I use it for without having bleed through, etc?

[gez]

If you do the bypass right, absolutely anything.

Edit:  Ah, you probably mean latching and not momentary, yes?  If you're thinking of plumbing it in to any old pedal, then results may vary.  If you use it with a little thought and additional circuitry, my first comment still stands.

[rockgardenlove]

It's just one of those standard wah pedal switches...I'd like to use it in something that doesn't suck much tone...

[gez]

So long as the effect has hi input impedance, then it should be ok.

[R.G.]

gez is dead correct - if the pedal has a high impedance input or a high impedance buffer in front of it, it *can't* cause treble loss problems.

See "The Technology of Bypasses" for how and why.

Put another way, *any* effect can use that switch if you put a high impedance buffer in front of it.

[Mark Hammer]

There are also other cases where cancelling the"effect" does not require bypassing the circuit itself, merely reconfiguring it.

Case 1: If you look at the schematics for just about any commercial modulation pedal, whether phaser, flanger, chorus, univibe, and sometimes many delay-based effects (e.g., reverb on amps), you will see that "bypass" consists of breaking one signal path.  On guitar amps, reverb and tremolo are cancelled by simply grounding out something, which an SPST can do.  On FET-switched pedals, you'll generally see one switching FET connected to the flip-flop circuit that simply lifts the connection between the modulated signal and the mixing stage that produces the effects by combining it with clean signal.  Even when FETs are not used, that arrangement has been employed. If I'm not mistaken, I think my old Boss BF-1 flanger uses it with a stompswitch.

Case 2:  Boosters are a regular favourite around here.  Many of them can be easily converted to "level-shifters" by using an SPST or SPDT to change between two gain-setting resistors.  For example,  Jack Orman's much loved MOSFET Booster has a delightfully high impedance input and adjusts gain amount via a single variable resistance on the MOSFET source.  So why not use an SPST to select between on-with-only-minimal-or-no-gain and on-with-more-gain? 

How?  Looking here - http://www.tonepad.com/getFile.asp?id=87 - you'll see a 5k pot that adjusts gain.  As the pot resistance gets higher, the 100uf cap factors less and less in setting the gain of the transistor.  So, if you had that 100uf cap normally connected to ground via a 100k fixed resistor, there would be little impact of the cap on gain (well, little gain, actually), but the cap would still have a nice path to ground where it could discharge so as to avoid popping.  If the 5k variable resistor (which maybe ought to be 10k in this instance) is connected to ground with the stompswitch, you instantly get whatever preset boost is determined by the pot setting, without disconnecting or reconnecting any caps.  The high input impedance hasn't changed between boost and no boost, just the amount of gain.

Similarly, assorted op-amp boosters/overdrives like the MXR Micro-Amp and Dist+ and DOD250/YJM308, etc, use a single variable resistance to set gain, with more gain added as the resistance is reduced.  You can easily stick in a largish value resistor (e.g., 1M) as the default resistance, and use the stompswitch to stick another variable resistance in parallel and get a volume boost.  Again, pop-free.

The only downside is that you don't have the extra set of contacts to do status LED switching.  Of course, as some people have reported lately, that invites its own set of switching-pop risks, so maybe you're better off without it.

[Skreddy]

Yeah.  And consider the delay: you'll want to enable the repeats to trail off when you "bypass" it rather than just cutting out suddenly.  Well, that should at least be an option.  Sometimes you do want to just shut the damn thing up.      But for the "trails" option, you'll want to keep a pass-through straight signal buffered and allow the repeats to keep trickling out of the delay section, of course mixing with the straight signal, until they die out on their own.  So you'll just be turning off the signal that goes into the delay section and not actually bypassing the effect in that case.

[rockgardenlove]

How about a FF?  That's high impedence, if IIRC from hearing it on here and looking at the schem.

[Skreddy]

How about a FF?  That's high impedence, if IIRC from hearing it on here and looking at the schem.

You talkin bout a Fuzz Face?  No, low impedance.  They made the originals true bypass even.

[rockgardenlove]

Ooops, I got it backwards...haha.