Improving the Coupling Capacitors for Better Tone Sounding

[CJ]

I never did like the sound of mica caps, now I know why

I always liked the look of the RMC ceramic caps with the green paint. Made them sound better.

I like the Fender 10 pf caps with the diamond logo but don't know who made them.

Polycarbonate caps have good tempco specs. Found this out in a 60 cycle oscillator for a power meter tester. The circuit was right in front of a cooling fan. The fan would make the frequency drift from 59 to 62 cps , polycarb fixed the problem.

FM discriminator coils use those weird dog bone caps for low L.

 

[soapfoot]

But is it audible distortion?

I’m not sure if anyone has ever devised a methodology to test this comprehensively

I suspect in the majority of cases the answer would be “no” (or at least “not reliably”), but probably not 100% of all possible use cases

A relevant set of accompanying questions may be:

In which specific applications are very small amounts of distortion likely to be significant?

Does changing dielectric material for every single capacitor in a device yield a different result than changing only one?

Do insignificantly-small amounts of distortion (by percentage) become significant if substantial amounts of gain are later applied (e.g. is the impact greater if the DUT is installed in a microphone before large amounts of preamp gain?)

Might non-objectionable (or even undetectable) amounts of distortion become significant if fed complex program material (of the type that might create intermodulation products)?

Might a listener become, with repeated exposure, sensitive to/aware of small distortion percentages that had been undetectable at first?

Etc.

 

[jokeramik]

But is it audible distortion?

Yes!

 

[CalavoBob]

Polystyrene are also good for the pF range, but they tend to cost even more (use them if you need higher V handling - then they may be comparatively cheaper than NP0/CG0). They may be better in tube amps because they are axial vs radial like MLCCs.

I do like the sound of polystyrene caps but their performance can go downhill in high temperature applications like tube guitar amps.

 

[CalavoBob]

I just tested some more 1uF non polar caps with that dielectric absorption test box that I posted a couple of days ago. The Wimas in that post had pretty low residue, but today I tested a 1uF 630V Solen MKP-FC metalized polypropylene, and it flatlined with almost no measurable residue. No wonder people like these. Best I've seen. Fairly small for 630V too. Might be too clean for a bluesy guitar sound, but it would be great in a clean preamp or mic circuit.

 

[jrg.roberts]

I had used, for my sins, to be inter alia the repair guy (one of an unending series) at Orange Music in London back in the late '70s, as well as doing hundreds of repairs for my own company, plus design and build stuff for bassists. Orange used to build their amps with whatever caps they could get cheap by the barrowload, just like Marshall, Vox, Sound City, Fender and everyone else AFAICS. The things that make the difference IMHO in a specific amp's sound are valves/tubes, bias, and of course transformers. Of course different caps may change things, but the change might not be an improvement. I had people coming back complaining about changed sound after repairs to factory spec, but usually it was that the valves or transformers had been changed and the bias put to where it should be as per spec not where it had drifted to after being on the road. Consistent valve amp sound is hard. Transistor amps were much easier. Now I use modelling to get where I want to go!

The capacitor thing is much more relevant in studio gear, but not much of it is wrongly or badly chosen. As far as tantalum is concerned, just say no except in timing circuits, and even then - must you? NEVER across rails. Fizz! Bang!

 

[opacheco]

I remember some years ago (15 years) when I started to work/service/restore Tube amps, Tube gear and vintage microphones, that many people advised to replace all old PIO caps for new film capacitors, in case there was any PIO in that specific old gear. The reasons were that:
- they didn't age well and are known to deteriorate over time, making them unreliable
- you couldn't depend on then and they can fail in a few different ways
- the dielectric can break down over time
- they can also leak, and once the oil leaks out of them they're useless
- could have corrosion around the edges and pins
- the paper can absorve humidity leading to breakdown

Probably some other reasons, I don't remember all.
But I did as the more experienced people advised, so I always replaced them in old equipment.

It was a surprise to me that in the last years a PIO Hype grew and people started to buy NOS PIO (NOS = OLD) caps to use them in their equipment. It seems they are now popular again for guitars, microphones and other gear.

I don't know if it's just hype and Snake oil or if they really sound better/different,
but I find it really funny that old caps once considered unreliable are now considered the holy grail for some duties.

Please listen to this video at 7:29 about the changing caps in that mics

https://www.facebook.com/share/r/oMBmfAvEwGmHKBPU/?mibextid=UalRPS

opacheco

 

[dai h.]

(I don't see a scrolling thing for the time in the Facebook video, so here is what appears to be the same video on Youtube FFed to the point he starts talking about the paper in oil caps and experimenting with changing them to mylar ones and "losing the magic": )