ye olde buffer conundrum

[hxlxfx]

hey yaal

so i wanna make some blend pots for clean/fx, where the fx are vintage fuzz circuits of my own build.
I get that i have to consider the load here so...

i've not been using buffers but know how to make some simple jfet ones.

question is...

which signals need buffering, and where?

i.e., do i buffer both the clean and the fuzz into the blend pot...??

my set up makes it notsoeasy to test configurations so i wanted a headstart!!

many thanks in advance for any advice

[R.G.]

which signals need buffering, and where?

i.e., do i buffer both the clean and the fuzz into the blend pot...??

You won't like the answer.  The correct answer is - it depends on the source impedance and the load impedance.

In the context of low and moderate signal circuits, buffers are devices to make the relationship of source and load impedance not matter to the circuits before and after the buffer. They are devices that make loads not overly load down sources.

So when you need a buffer is dictated by the relative magnitudes of the source and load impedances, including taking into account what those impedances do with frequency.

The reason guitar pickups need buffers is that they have a rising impedance with frequency, so their source impedance is much higher at treble than bass, and if you load them much, the treble is lost more than the bass.

In a blend circuit, you're looking at two source impedances and three loads. The two signal source impedances are obvious, but the blending pot(s) load each source, and are themselves loaded by whatever comes after the pot(s). The clever, insightful, skilled way to do this is to know the source impedances and final load, and calculate whether you can get away without a buffer because the loading is not "too much".  "Too much" is in quotes, because you have to decide what that value is, whether by calculating or by ear.

The quick and dirty answers are:
1. Try it, and use buffers if you don't like the sound.
2. Use three buffers, listen, then remove them one at a time.
3. Calculate the signals and impedances and act accordingly.

[nocentelli]

Two things to consider when trying a blend for (vintage) fuzz effects:
1) input buffering is required, yet many fuzzface and similar vintage era fuzz pedals are so much fun because they clean up wonderfully with the volume pot: buffers can seriously mess with this response.
2) having a clean guitar signal paralleled with fuzz brings some peculiar inversion to the usual playing dynamic/fuzz "amount" interaction. Louder notes will be limited by the fuzz and less noticeable, but quieter playing will be compressed and come through above the clean sound.

I'm not trying to criticise the idea: I find a blended fuzz works well for mangling loops of guitar, or synthy complex lines, where the fuzz can be blended slowly in over time, but as an effect to play guitar through, it has some unusual and counterintuitive effects.

[bloxstompboxes]

666 posts nocentelli.

[blackieNYC]

My fuzz face doesn't sound good with any buffer in front of it. But blended with something else, maybe it would add something nice to the mix.  My mosrite fuzz sounds great with a buffer or boost in front.
Build a splitter blender, you'll need both.  I suggest the op-amp variety
http://www.runoffgroove.com/splitter-blend.html
I think I prefer two pots to mix with, instead of a blend:
http://www.diystompboxes.com/smfforum/index.php?topic=76889.0