Why do preamplifiers have so many capacitors?

Or, if you want a more formal textbook, 'The Art of Electronics' by Horowitz and Hill is a bible of practical methods. A section  in Chapter 1 talks about capacitors and their different characteristics.

But also note that although materials are a good guide to how a cap will sound, the method of manufacture also makes a big difference. For example, a Relcap teflon film and metal foil cap sounds quite different from a V-cap. To me. YMMV

I think my sanders preamp has 20K of capacitance

 very very accurate and closest to straight wire with gain ve ever heard

unforgiving pre!

but, a good recording is just that, sounds flawless

unanswerable question without more data. But as many have mentioned, there are many solid reasons to use capacitors. If we simply accept you assertion that some preamps have a relatively large complement, the quick answer would be "because they need to isolate lots of inputs and outputs". But that's pure speculation.

Why in fact do so many recipes include a lot of garlic? Maybe we ought either ban garlic or add it to cakes!

I'll also note that ot all capacitors you see are actually directly in the signal path, and that there are many engineering solutions to the non-linearity of common electrolytic capacitors. While the purist in me wants to eliminate them, more often i find that they free me to make bigger improvements and its often worth the "cost"

All capacitors are not the same and resistors also.  Just rebuilt a very high end DAC with better capacitors.  Improved the openness, separation, dimension, speed, clarity, tone, etc.  Close to 50 capacitors were replaced.  All other responses above are part of the equation.

Happy Listening.

Bigkidz

That's some serious stuff to be replacing 50 capacitors. What type of beastie Dac are you dealing with? Would love to learn more about all that you have done here. Clearly you must know a little bit about what goes on inside a box.

I commend you sir