Parallel Looper

[Khas Evets]

I'm building a 6 loop true bypass pedal - my first project! - and I want to add the option of switching between parallel and series effect ordering. I was hoping to keep everything passive, but I'm concerned about splitting a signal six ways. I've seen the schematic for the mixer that uses buffers, but I was hoping to keep it simple.

1) Do I need to buffer the signal?
2) If I do need a buffer, do I need a buffer for each loop or can it share one buffer?
3) I'm planning to build a booster next. Would a booster in front solve the problem?

[niftydog]

1) Do I need to buffer the signal?

Yes. If you intend to feed one signal into six effects units in parallel, you'll definately want a buffer.

2) If I do need a buffer, do I need a buffer for each loop or can it share one buffer?

one well designed buffer should do the trick.

3) I'm planning to build a booster next. Would a booster in front solve the problem?

probably not. It's not about levels it's about impedances.

Say you've got six pedals, each with a 10k input impedance. Hook them all up in parallel and suddenly your effective input impedance is 1.7k. in other words, the current demand on the input signal is increased by a factor of 6!

[Khas Evets]

Thanks. There are several buffers floating around. Is there one you would recommend?

[niftydog]

nope. I tend to design my own. simple op amp buffers are a breeze to design and there's plenty of resources around the place. You can't go too wrong.