Capacitors.. which ones for which applications?

[Steve Conner]

Yep, they're all considerably more rugged than, say, germanium transistors. Most RF coax cable has a polystyrene dielectric and is difficult to solder, because if you're not quick the dielectric melts and the core shorts against the screen. But that doesn't seem to be a problem when soldering capacitors.

Some amps I've seen used polystyrene film/foil caps in the tone stack positions where Fender would have used disc ceramics. These caps don't have any outer casing and look like tiny Swiss rolls.

Electrically they're probably no different to a silver mica cap, although they have more self-inductance that makes them a bit useless for RF. I prefer them to silver mica or ceramic for my own amp building, though I'm not exactly sure why

[tubeswell]

These caps don't have any outer casing and look like tiny Swiss rolls.

I prefer them to silver mica or ceramic for my own amp building, though I'm not exactly sure why

Hmmm... when you build these amps, you're not going without enough to eat are you?

[Tele-Cat]

Yep, they're all considerably more rugged than, say, germanium transistors. Most RF coax cable has a polystyrene dielectric and is difficult to solder, because if you're not quick the dielectric melts and the core shorts against the screen. But that doesn't seem to be a problem when soldering capacitors.

Some amps I've seen used polystyrene film/foil caps in the tone stack positions where Fender would have used disc ceramics. These caps don't have any outer casing and look like tiny Swiss rolls.

Electrically they're probably no different to a silver mica cap, although they have more self-inductance that makes them a bit useless for RF. I prefer them to silver mica or ceramic for my own amp building, though I'm not exactly sure why

I always use an alligator clip attached to the lead of any cap I'm soldering - acts as a heat sink. I've burned my fingers a few times taking the clips off the leads but a lot of heat was kept away from the cap by doing that.

[Jazz P Bass]

Cap tolerance

Just thought I'd add my two cents to the tone debate.
The key word in my mind is the tolerance of the capacitor.
Plus or minus 20-30% is huge when talking small value caps.
Is the actual change in capacitance what people hear as a change?

[Steve Conner]

Quite possibly, yes. Earlier I mentioned a properly controlled test, and one of the controls would be to check that all of the capacitors under test were very nearly the same capacitance. If the tolerances were wide enough to make more than about 0.5dB difference to the tone, I'd select them.

But to be pedantic, 20-30% tolerance isn't any worse for a small value cap than a large one. It's still 20-30% of the capacitor's value, no matter what the value is.

[rockon1]

Just jumping in here trying to learn. Great stuff! So it would be OK to swap an .0022 400v poly with a ceramic disc type of the same value? They seem so small in comparision. bob

[guitician]

Caps all have their particular applications, that's why their are so many types. I realize that the "Sound" of the cap is very subjective too. But in any application, physical aspects, that are not part of the capacitors specs, will still come into play and change your outcome.

[Enzo]

A .0022 400v of any type will work is a circuit calling for such a part. You may or may not hear some subtle difference, but the circuit will work fine.

[rockon1]

A .0022 400v of any type will work is a circuit calling for such a part. You may or may not hear some subtle difference, but the circuit will work fine.

Thanks . Just seemed odd they would use such a big cap when a smaller one would do. Bob

[Rhodesplyr]

I do believe that you should avoid ceramic caps in an audio signal path, though. They can be non-linear (capacitance changes with voltage) and microphonic.

I've often read this, but I think it needs a little refinement because there are so many different types of ceramic capacitors.

Pure ceramic capacitors, NP0 / C0G types, are actually very good. I've seen distortion tests on them that found them only slightly inferior to polystyrene. They are also very stable and heat-tolerant. The downside to these is that they are only available in small values, often no more than a few hundred picofarads, due to size.

To get more capacitance in a smaller package, the ceramic is doped with various compounds to increase its dielectric constant. This is the case with Z5U and X7R types you find in some audio equipment. These are the "bad" ceramic capacitors that have given all ceramics a bad reputation. They can change value with temperature, applied voltage, and age, and they can be piezoelectric or microphonic. They are essentially cheap substitutes for film caps in audio signal paths.

I've replaced some Z5U types with mica or film capacitors with very positive results, especially the REALLY tiny ones that started appearing in the 1980s. If older discs are C0G or NP0 (or NP750, NP1500), I leave them alone.

Don't tar all ceramics with the same brush, especially below 100pF :-)

[Enzo]

You may have a point being fair to ceramic caps, but when the cap in question is a .01, your fave NPOs don;t make it onto the playing field, and by elimination making all the remaining ceramic candidates "bad."

[Steve Conner]

That's a good point though, are the ceramic discs originally used in Fenders the "good" type or the "bad" type?

The Z5U and X7R types usually have a lower working voltage, as far as I know, so might not even be usable in a tube circuit.

[Enzo]

Dunno. I just used my incredible troubleshooting powers to decide if the capacitance range of the "good" type don;t go high enough, then they must have to be the "bad" ones.


Didn;t think any farther than that.

[Gollum]

I'm not going to pretend that I truly KNOW anything here, as I'm relatively new to the electronics game as well. I've been toying with a soldering iron for a decade now, since I was a wee kid, but that makes me no expert.

But, to play devil's advocate here I'm going to mention something I read in "The Guitar Amp Handbook" by Dave Hunter. He interviewed many of the "greats" when it comes to guitar amp building, one of which being the late Ken Fisher. This interview with Ken was great and I found it very enlightening. It was interesting to hear one of the biggest amp gurus that's walked this earth to talk about the difference between all these different parts, but to sum most of it up that you can make the amp sound good dispite what you use.

Unfortuantely he didn't talk much about capacitors, but I'm betting his statements should give a clue to the fact that design tolerences can be made up for. If two caps of truly the same value sounded different, you could probably make up for it elsewhere if it was a problem.

The only design aspect that Ken speaks specifically about is resistors, in which he always prefers carbon film over metal film.

He even goes on to talk about how overhyped transformers are.

But also remember that this same man will talks about the flow of electronics in extruded metal and how wire is directional, and he made sure his amps were wired directionally correct, since wire conducts better one direction than the other........

Some other food for thought is that many of the interviews in this book are contradictory, that is to say that even the great amp builders out there don't agree, or at least go about the same goal in vastly different ways. A Dr Z isn't made like a dumble, and a dumble isn't made like a matchless, but they all sound good in their own right.

Oh, another point to be made is that Ken Fisher sold his amps for less than nothing compared to their market value, even long before he died. He didn't make them for huge profit, and didn't put the most expensive parts into them. He was able to make amps to sell between $1,000-2,000 hand wiring them in the USA. There's no way he was using top shelf parts, so obviously you don't need to spend a ton of money to get amazing tone.

[Tele-Cat]

On the other hand, I've spoken to Skip Simmons who says caps and transformers are uber-important.

Opinions are like...well, you know.