Buffered/true bypass switching

[Zanius]

I'm putting together a looper and wanted to put a switchable buffer for the loop in there. So the question is, can I use a spdt switch wired like that?

1- input jack (and also going to buffer input)
2- output jack
3- buffer output

In most cases buffers would have a pulldown resistor in their input, wouldn't that mess with the impedance when switch is is in the "up" (true) position? I will use a dptd for now. :)

[Ciaran Haslett]

If you have anything hanging off the input at all then its technically not "true bypass" at all.  Whether at matters in this case I couldn't tell you without trying first but I'd imagine any filtering/active semiconductors etc will still be trying to do what they do only with a floating output.

[Zanius]

Yeah, the more I think of it, the more stupid it sounds. Maybe it could work for a specific design, but for a generic looper, it would surely cause problems. Also, where there is space for a spdt there is space for a dpdt too, so no point messing up your signal.

I guess I got the idea from the buffered bypass scheme of old buffered pedals like the crybaby which uses a spdt footswitch. But there you never bypass the buffer so there's no problem.

Thanx for the answer Ciaran!