Why do preamplifiers have so many capacitors?

Filtering and stabilizing power, DC blocking and coupling between amplification stages, frequency adjustment etc. Some may be paralleled so smaller caps fit in case.

8 to 12?

Really depends a lot on the type of preamp.  Caps do all sorts of important duties.  From converting AC to DC, stabilizing voltages,  blocking DC in the signal path, limiting the preamp bandwidth, setting the time constants for muting circuits...

I suggest the best way to learn more is to maybe build a kit. :)

What preamp are you referring to specifically. 

If the pre has a phono preamp section, caps are needed for the RIAA equalization which has a 40 dB bass to treble swing in its curve in order to get the signal back to a flat response.  Tone control circuits also need caps.

Which preamps have the best use of capacitors and tubes? Since that seems to be really important for preamp.

am told Teflon capacitors are really good and use of foil, whatever that means

Jumia,

You are looking at this the wrong way. You are trying to evaluate the ride of a car based on the color of the brakes.

While it’s good to understand the composition of your purchase as one way to evaluate the financial outlay at the end of the day the only thing that matters is performance. To reuse the car metaphor, do you like the ride or not?

Only after you have spent time figuring out what kind of ride you like, then you start looking for patterns.  "Oh, I really like the sound of x tubes or wax/paper capacitors..."

If you try to look at parts first you'll never figure out what kind of listening makes you happy.

Best,

Erik

I dare say many who buy preamplifiers have no idea how they work internally. It would be wonderful if there was a diagram, a visual guide, allowing someone to understand the internal flow of a preamplifier. Further I never see commentary explaining the flow, and variations, within a preamplifier.

I think many would be grateful with something that illustrates how these mystery boxes work.

Look at a schematic (circuit diagram) to see how parts are connected. 

@jumia-

        IF you are sincerely interested; the first few magazines/books/resources mentioned on the following link, are an excellent place to gain such knowledge.

         They were great to, "grow up" on and: even decades old, they're still fun to bring out and reread.

                          I miss the DIY/hobbyist PAPER rags!

                       http://www.nutshellhifi.com/Linkstxt.html

@jumia-

     Actually: what was supposed to be a link to the following Vacuum Tube Valley site and reprints, wasn’t, on the last reference.

                               You’ll find some good articles, here:

https://web.archive.org/web/20130604042043/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/vtv.htm

     Be patient, as you're downloading a complete magazine, in pdf form, for each issue.

Watch some of Ron Sutherland videos.

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