Input Impedance

[grapefruit]

I'm building a frequency splitter for bass guitar. (lowpass and higpass filter so the top and bottom end can be processed seperately). I'm wondering how high should the input impedance be coming back in from the effect loop. I could save an op amp if I just have the loop coming straight into a 50k pot and then into a 47k resistor into a summing op amp. But I'm figuring because some fuzz boxes have a pretty high output impedance I should put a buffer in front of the volume controls.

Any opinons on this??

Thanks,
Stew.

[R.G.]

Opinions won't do you much good on this one. Mother Nature will make it work however it works depending entirely on what you hook up to it. No one's opinion will help.

But fortunately, you don't need opinions. For the cost of an NPN or a JFET, a few resistors and a couple of caps, you can put a follower buffer in there and still not use one more opamp. It works fine for all the Ibanez pedals. If you put in a simple buffer, you don't use another opamp and you cover all the bases.

But you did ask for opinions. Some effects use as high as 100K for an output volume pot. The max impedance out of that will be 25K. If you have an input impedance of at least 250K, it will not load down a 100K pot significantly. The opinion is - you could probably get away with as low as 100K.

[grapefruit]

OK, I'll just put buffers in there and be done with it. That way it will handle any output.

Thanks.