Power supply caps

[scaesic]

I intend on using a 120VA 15-0-15 transformer for a tda2050 project im currently working on.

I want to use the power supply to give +/-15 v regulated to the tonestack and +15V to the pre amp, so i am going to use abipolar design using regulator chips.

I have two questions. 1/ in the ggg bipolar design i can see two caps in parrallel on the + and - lines before the regulators, namely a 1000uF and a 0.1uF.

what is the 0.1uF for?

I was planning on using a pair of 4700uF and 1000uF caps to give a combined 5700uF smoothing, should i include a smaller cap for something?

Second question 2/ i plan on using +/-20V coming straight out of the smoothing caps to power the tda, will this mess up things at the regulators?

p.s what output cap is reccomended? gg says 0.1uF and geo uses 10uF

[R.G.]

1/ in the ggg bipolar design i can see two caps in parrallel on the + and - lines before the regulators, namely a 1000uF and a 0.1uF.
what is the 0.1uF for?

Large electrolytic caps become inductive at high frequencies. The 0.1 is to offer a low impedance at high frequencies and RF.

I was planning on using a pair of 4700uF and 1000uF caps to give a combined 5700uF smoothing, should i include a smaller cap for something?

It's a good idea, although you can often get away without it. The smaller ceramic (make it ceramic or film) cap is there for things that happen sometimes, not always.

Second question 2/ i plan on using +/-20V coming straight out of the smoothing caps to power the tda, will this mess up things at the regulators?

That's three questions 
No, no problem.

p.s what output cap is reccomended? gg says 0.1uF and geo uses 10uF

That's four questions   
Probably both together. The regulators don't much care. The output cap on the regulators is there for low impedance at ultrasonic and RF frequencies where the regulator can no longer regulate. Many of the app notes suggest values between 0.01uF to 10uF. Don't go crazy here, 10uF is all you're likely to need. But the exact value is not crucial.

[scaesic]

bah! the first and second questions were practically the same thing!

i should of thought to look up the regulator data sheet, thanks for the explanation of what the smaller caps are for though!