Ceramic cap dielectric types

[chopstuck]

Ceramic cap types.
Found this interesting graph.
If the unit change is to be believed, it looks like anything but NPO /COG would be useless but what about the whole tone changing as the amp warms up phenomenon?

I know that the disc caps used in our favorite amps were probably the cheaper type.
Does anyone have experience with the more stable dielectrics ?
Seems the X7R may be acceptable too, unless the inside of the amp gets up to Vox levels of heat.

[Leo_Gnardo]

That's 'zackly why I recommended NPO. Now if Chopstuck Amp Co is going to build a million Belchfire 500 amps and you want to save lots of dough on caps, you buy the drifty ones cheap and to heck with what they sound like, or have any effect on EQ or bandwidth, warmed up or not. That's the manufacturing frame of mind for almost anything, not just amps.

You're probably willing to spend a little extra for quality parts, go go go for the N P O. And you won't be able to blame them for tone changes as the amp warms up. Just resistors, tubes, and transformers. Isn't that enough?

[gingertube]

The problem with ceramic caps is dielectric absorbtion which introduces significant distortion.

The HiFi "nutters" simply will not use them in any amp, tube or solid state.

We would of-course look very foolish if we objected to distortion in a guitar amp.

I tend to avoid them in guitar amps too but thats just personal bias based upon my experience with them in solid state HiFi Amps - I found (in those HiFi Amps) that the distortion they caused was very objectionable.

Cheers,
Ian

[Leo_Gnardo]

The HiFi "nutters" simply will not use them in any amp, tube or solid state.

Funny 'nuff the nutter's playback gear may not have any ceramics, but the studio gear it was recorded on had plenty. LA-2A compressor, open the front panel & the first thing you see is nice big yellow discs. And that's just one example. Insides of all those old amps too, Jimmy P's Supro recording amp wouldn't sound so deliciously snotty without 'em. "Oh but we must record and mix and especially listen back to that with only the finest..." 990 discrete op amp - the "sound" of all those 70's hits, select hi quality discs in there too. Mix consoles were crammed with 'em. Don't tell the nutters.

For a currently built amp I'd avoid discs except for a few select functions - good NPO's sound just fine as the treble cap in tone stacks. You can spend a bit more for silver mica if you want, no problem. If I was building a new amp to sound "on purpose" old-fashioned funky, ceramics would be a major part of the formula.

[chopstuck]

Leo, maybe Ima (See what I did there) maybe Ima looking for the a tone that comes only from a few choice ceramics.
I built my first D-lite with Mica and really couldn't get anywhere near the interesting tone I had imagined was there.
The next amp was an Ambassador 30 4x6V6 clone that was fair with polystyrene, harsh with mica and mega neato with ceramic caps in the tone stack.
I have my doubts about larger value caps (.001-.1) but they were in many of my old Dynaco amps and I recall they sounded pretty good.
I like just a few in there for color.
Probably the most bang for my buck when it comes to component choice.

What vendor has your choice ceramics ?
Do you have a favorite brand or are they pretty much the same (global sourcing etc) when the spec is met ?

[Jerryz1963]

I was just directed to an article on caps by a friend. very interesting.
Apparently, use of the ceramic adds "crunch." Not being anything but a rank amateur on the guitar, I'm not even sure what "crunch" is, but I'm guessing this is why Fisher put it in his fabled Trainwreck. He paralleled it with a polypropylene as I recall. So, there may actually be a legit reason to use a ceramic cap in a guitar amp. In this article, the guy had scope displays so you could see how different caps behave. just for fun, he also displayed some of them in parallel. BTW, would anyone care to explain "crunch?" Sorry about my noobishness