Jfet buffer/splitter cap value

[vacuumdust]

In most simple jfet buffer schematics the output comes off the source through an electrolytic cap...generally 1uf to 10uf. I'm looking to build a signal splitter using one of these buffer schematics but I only have 47uf caps on hand. Lots of explanations of this little circuit but not much mention of that Output cap and how essential it is that the value is 1 or 10uf. Here's the schematic I plan to follow ..this one has 1uf. Can anyone help me understand the reasoning behind choosing the value for this cap. Thanks!

[vacuumdust]

Here's the schematic..
http://www.muzique.com/lab/splitter.htm

[PRR]

Bigger is better (within reason).

47u will suck-up crap on long lines better than a smaller cap.

Usually 10u or even 1u is "good enough", a penny cheaper, a mm smaller.

My garage loft needed a 4x4 post support. Foo, I used a 12" tree-trunk. The tree was handy, I'd have to go out to get a little 4-inch stick. The extra heft, and rounded (kind to car doors) shape, are bonus, like the super-low impedance of a 47u is your bonus.

[vacuumdust]

That's great!  Thanks so much for your explanation.

[duck_arse]

with all respect due to PRR, the output cap can be too big. at 47uF, it might cause blocking or gulp distortion. if so, you know you need a lower value. if it is a supply bypass cap, then Paul's comments do apply.

[antonis]

Output cap (as well as Input cap) mission, other than blocking DC, is to form a HPF with any impedance coming right after it..

If we don't know (or can't estimate) following impedance, oversizing is one-way solution..
(although, IMHO, 1μF should be adequate unless next effect exibits an input impedance lower than 10k..)

[PRR]

> the output cap can be too big

Depends.

Blocking requires a non-linear load. Load has not been specified. If an input is non-linear, it probably should take charge of its own blocking, not depend on the source having a quick recovery (low-C).

A smaller cap won't eliminate the blocking. Only shorten the "gulp" period.

But yeah, in guitar-boxes you do find some funny interactions.