What type AC coupling capcitors do you use for input and output stage?

[Fusion916]

What is the best type of capacitor for AC coupled input and AC coupled output? I'm assuming polarized electrolytics are not the best type.

 

[john dozier]

Teflon or polystyrene. But they are BIG! Regards

 

[nigelwright7557]

I use polarised electrolytics and have no problems.

 

[Dave Zan]

I am about to use AC mains power motor capacitors.
Reasonably priced with excellent electrical properties but probably best to hide them because people will inevitably think that such an industrial component must sound industrial.

Best wishes
David

 

[john dozier]

Those are ususally metalized polypropolene and can sound very good. I do not use in the signal path, however, only in the ps. If you need high value in a small space, try niobium oxide. They are only as SMDs however. Regards

 

[Fusion916]

Just to make it clear, I'm talking about ac caps in the signal path, as coupled input and ac coupled output.

 

[john dozier]

I understand your question.The best is any film and foil-teflon first, then polystyrene, then polypropolene. I would avoid mylar or any electrolytice unless absolutely necessary. What values do you need? What size can they be? You really need to specify those two parameters before the question can be fully answered. Regards

 

[KatieandDad]

Some people would disagree MKP (Polyprop) over MKS (Polystyrene).

 

[Rod Beauvex]

Not to derail the thread, but could someone remind me what Mylar's are? Are those the same as polyesters?

 

[chris719]

Mylar is polyester yes.

I don't know how Teflon or polystyrene are very useful for coupling, they are barely available and in tiny values. For normal solid state equipment input Z the best you will find is probably metalized polypropylene (easily available up to <100 uF). Failing that, try a very large value bi-polar electrolytic like Nichicon Muse ES or Panasonic SU.

 

[jean-paul]

Hi in the past years I ranked the various film caps as follows:

1. Polystyrene (KS) and/or Teflon
2. Polypropylene (MKP/FKP/KP)
3. Polycarbonate (MKC)
4. Polyphenyl Sulphide (PPS)
5. Polyester/Mylar (MKT/MKS)


Katieanddad: Polystyrene is not MKS ! It is KS. MKS is polyester. I think most abbreviations come from Wima and other long established brands.

Positions 3 and 4 might be interchangeable varying from brand and series. MKC is very rare nowadays as they are not being made for a long time. Please mind that some manufacturers make very good polyester caps that outperform polypropylene caps of other manufacturers (sound wise). Same counts for BG NX Hi-Q that outperform MKP caps while they are bipolar electrolytic caps !

 

[KatieandDad]

I used 10uF PIOs as outputs and 1uF MKP for input.

PIOs are a bit on the large size but are not STUPIDLY expensive. I think I paid about £18 GBP each for them. They are about the size of a 200mL drink can.

 

[jean-paul]

Paper in oil (PIO) caps are the most coloring of all. I would not rank them as film cap.

 

[analog_sa]

I always thought the sole purpose of SS audio was to avoid coupling caps

 

[jean-paul]

Very sharp comment ! Direct coupling is the best cap but over the years I learnt that some caps in the chain can be OK to protect tweeters

 

[KatieandDad]

Paper in oil (PIO) caps are the most coloring of all. I would not rank them as film cap.

TBPH I couldn't hear any difference between the PIOs and the MKPs they replaced.

 

[jean-paul]

Then replacing the MKP caps was useless The MKP were probably a lot smaller too.

In general PIO are warm sounding caps that add something. They are generally not neutral but if yours are then you can be satisfied.

 

[Ian Finch]

Like all cap comparison threads, this would be useful discussion if we knew what device the OP was referring to. Since this is the solid state amplifier forum, we might assume the input cap will be ~1uF and the output will be >1,000 uF. Many of the preferences discussed here will thus be irrelevant since it will mean electrolytics at the output in practical applications.

If you want to see endless rounds of learned and not so learned discussion and read papers about small signal audio capacitors, you can wade through John Curl's endless "blowtorch" thread in the "analog line level" forum. There other interesting threads there too

 

[hazard500]

I've got sick of trying different capacitors, so I've gone to transformer coupling. My balanced DIY jfet RIAA stage takes the output from the drains of the LTP fets in the last stage. I now use a Lundahl LL1527XL across the output, it is much more transparent than any cap I've tried. Of course, this is easy with a balanced output as there's no DC through the tranny, single ended operation may be more difficult.

 

[stratus46]

I always thought the sole purpose of SS audio was to avoid coupling caps

You'd get a chuckle out of the analog HD video processing I did for a flying spot scanner about 10 years ago. In the RGB video channels there is 1 in line capacitor in each channel and its actual purpose is sample and hold. All told over 200 opamps and multipliers direct coupled.

While analog audio would be difficult to get that low a capacitor count, I can envision numbers in the single digits without much difficulty. If caps sound bad, don't use them - or perhaps they're not as bad as we think.

G²