Which Capacitors for Audio?

[JohnRoberts]

To quote the late and great J. Gordon Holt from 1962:

"High fidelity may be a science, but it isn't an exact science. There are enough things about it that aren't understood to leave room for a goodly amount of educated opinion.

.....

This raises the question of whether high-fidelity can, or should be, better than the real thing.

.....

Sound recording may eventually become a creative art in its own right, producing musical sounds that bear no relation to any natural sounds. Indeed, some branches of it—pops and so-called electronic music—are already well on their way in that direction. This is not high fidelity, though, and there's no sense pretending that it is."

I suspect it was more true to the source.

Thor

Sonds like JGH was selling his book (magazine). If audio was settled science there would be nothing for him to write about. While there have been more than a few audio technology advancements since 1962.

JR

 

[terry setter]

Sound recording may eventually become a creative art in its own right, producing musical sounds that bear no relation to any natural sounds.

Yes, and we must tip our hats to the "sound designers" for film who are tasked with coming up with believable sounds for things that don't even exist, like light sabers.

(Re: preferring a sealed enclosure to one using a Dynaudio Variovent) I suspect it was more true to the source.

Yes, in respect to the "pressure" characteristic that I experienced. But I can also imagine that my preference might have been highly room dependent, and that, in the right room, I'd have preferred the Variovent. I had a friend who was an eminent physicist. He once told me that he had originally planned to go into acoustics, but lost heart when he realized that merely placing an over-stuffed chair in a room could seriously alter the acoustic conditions he had worked so hard to create. He said that he much preferred the predictability and consistency of sub-atomic particles.

 

[thor.zmt]

He said that he much preferred the predictability and consistency of sub-atomic particles.

Great sense of Humor, not that he is wrong though.

Thor

 

[Gus]

Stacked film is wound
Page 6
https://www.tdk-electronics.tdk.com...1513474ba/pdf-generaltechnicalinformation.pdf

 

[terry setter]

Great sense of Humor, not that he is wrong though.

Yes, his humor was dry as a bone, but always worth paying the extra attention that was needed.

 

[thor.zmt]

Stacked film is wound

Yes and no.

Unlike traditional axial wound capacitors there are no voids and the actual capacitors structure is made of nearly parallel flat sections of film...


And there are other benefits. It is worth actually reading the whole App note:

Film Capacitors - General technical information

Thor

 

[Tubetec]

I know stacked foil alright ,
Isnt it a layer of glass on the outside ?
They have a welded connection at either end that can fail , Ive seen that happen , of course there is also uninsulated parts as well .
I get the bit about these caps having no voids as each layer is layed flat and bonded , then the material is cut to the size required for a given cap value . I only ever used this type once for audio, as a coupling cap in a 12ax7 based preamp , it worked and its small lead spacing allowed it jump the gap across the tube base perfectly .
They do seem to be some of the smallest foil caps you can get , and available in high voltage types upto 400v from Cricklewood .
My guess is these solid capacitors may do a bit better regarding physical vibration than the usual wound type . Low voltage varieties (50v)dont seem to be that common anymore but could be used in place of electrolytics by parralelling up a block of them ,

The only thing I dont like about these caps is the lack of insulation and the not so strong spot welded terminations , there made of very brittle material , It might be possible to dip them in epoxy to fully tropicalise them and give extra support to the leadouts ,

The compact size/high voltage rating and low microphony might make these a good choice for a tube mic coupling cap , a layout that has options for multiple coupling caps in parralel can be finely tuned or voiced when its finally paired up with a transformer ,

One final thought ,
these type of block caps also have low inductance , because the structure itself isnt wound , with its discrete layers +-+-+-+- back and forth it posseses a non inductive quality .

 

[CalavoBob]

I'm having a hard time locating stacked foil film caps (preferably polypropylene) below 33 pF to 10 pF for use around feedback resistors in OP amp circuits and in filter networks for my audio studio projects. The regular trustworthy distributors don't offer values down that low. I used to use polystyrene caps for this decades ago and really liked their sound, but they don't age well when equipment gets warm, and manufacturers have pretty well moved away from making them anymore. (I've still got about twenty beloved 10 pF polystyrene caps in my old stash). I've been using MLCC COG caps for this small picofarad range lately because of their low ESR and availability but I'm not convinced that they sound better than the polystyrenes did. I have noticed that mica caps are available in this range and they are highly recommended for radio use but I really don't hear much talk about people using them in their fine audio work. I did use some micas in some precision gain networks I designed for a couple of Telefunken V72 mods because that was all I could find in those values, and they certainly got the accurate dB steps I needed but I really didn't have other low value dialectrics to compare them to for listening tests. Has anyone out there done listening tests comparing low value picofarad micas to stacked polypropylene or polystyrene caps? Are there reputable sources for PP or PS caps in low picofarads? Like the rest of you guys, I'm just looking for audio quality that supports that suspension of disbelief. Audio dreamland. mmmmm.

 

[Somkereki]

My experience with mica capacitors is favorable. Although I mainly tried military capacitors with Russian silver electrodes. Hungary used to have a serious military industry, which is why the remaining sets were available. In practice, I liked the sound better than the polystyrene capacitors. His explanation, these silver-mica capacitors were inductance-free and aging-free. Their only drawback was their larger size, as they were only produced in the upper voltage range. But they fit in a tube studio microphone. I regret in retrospect that after the breakup of the Soviet Union, I did not buy a larger set of such capacitors, which were available very cheaply.

 

[ct.waveform]

I'm having a hard time locating stacked foil film caps (preferably polypropylene) below 33 pF to 10 pF for use around feedback resistors in OP amp circuits and in filter networks for my audio studio projects. The regular trustworthy distributors don't offer values down that low. I used to use polystyrene caps for this decades ago and really liked their sound, but they don't age well when equipment gets warm, and manufacturers have pretty well moved away from making them anymore. (I've still got about twenty beloved 10 pF polystyrene caps in my old stash). I've been using MLCC COG caps for this small picofarad range lately because of their low ESR and availability but I'm not convinced that they sound better than the polystyrenes did. I have noticed that mica caps are available in this range and they are highly recommended for radio use but I really don't hear much talk about people using them in their fine audio work. I did use some micas in some precision gain networks I designed for a couple of Telefunken V72 mods because that was all I could find in those values, and they certainly got the accurate dB steps I needed but I really didn't have other low value dialectrics to compare them to for listening tests. Has anyone out there done listening tests comparing low value picofarad micas to stacked polypropylene or polystyrene caps? Are there reputable sources for PP or PS caps in low picofarads? Like the rest of you guys, I'm just looking for audio quality that supports that suspension of disbelief. Audio dreamland. mmmmm.

Farnell have got 22pF in polystyrene, but you'll have to wait till Christmas for them. They may have more in that range of polystyrenes but I didn't check by value. Otherwise it's going direct to the manufacturers - or using smaller resistors.

 

[Newmarket]

And non-metalized basically means film/foil?
Could you maybe name several types?

Well it's just film/foil.
As opposed to "metallised foil" etc.

 

[Chandra]

I'm having a hard time locating stacked foil film caps (preferably polypropylene) below 33 pF to 10 pF for use around feedback resistors in OP amp circuits and in filter networks for my audio studio projects.

Those days, in radio circuits, we used a few cm long thick insulated wire and wound a finer insulated wire over it (10 to 20 turns) for 3 pF to 30 pF. Both wire ends were soldered as a capacitor.
Regards.

 

[Mr. Moscode]

Those days, in radio circuits, we used a few cm long thick insulated wire and wound a finer insulated wire over it (10 to 20 turns) for 3 pF to 30 pF. Both wire ends were soldered as a capacitor.
Regards.

AKA - A gimmick capacitor.

 

[Chandra]

That is how they fine tuned RF circuits. It is OK that you don't have that knowledge.
Regards

 

[CJ]

And inductors could be wound on a resistor body and then slid off for Hammies on 10 Meters,


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[CalavoBob]

I've made a 50 ohm to Hi-Z transformer by winding fine magnet wire around a pencil to couple a Wheatstone bridge (that had a 433 MHz antenna in the test leg) into an RF spectrum analyzer to check the operating frequency of the antenna. It actually worked!

 

[Matt Nolan]

AKA - A gimmick capacitor.

Yeah. Those guys that used them in the feedback loop of the Siemens V77 and similar mic preamps were all about gimmicks.

 

[thor.zmt]

Those days, in radio circuits, we used a few cm long thick insulated wire and wound a finer insulated wire over it (10 to 20 turns) for 3 pF to 30 pF. Both wire ends were soldered as a capacitor.

As alternative, 50 Ohm coax cable is 100pF/ 1m, comes in PTFE with small diameter and is good for single pF values. It's even adjustable by sliding the center in/out.

Thor

 

[Somkereki]

Yes, I also used the inner dielectric of PTFE coax cable to make a very good quality 1 pF high voltage capacitor. Although I was surprised that the PTFE did not deform even at 450 degrees Celsius. Setting the WSD-81 Weller soldering iron to 450 degrees, I pressed the tip to "PTFE" for a minute and there was no trace left. It was the internal dielectric of a silver-plated coax cable made by Habia. I used the same cable as the pickup cable of my Ortofon VMS 10 E Vynil turntable and I got an incredibly beautiful clear sound image. Even PE cables have a nice sound, but PVC cables are horrible!

 

[Somkereki]

Farnell have got 22pF in polystyrene, but you'll have to wait till Christmas for them. They may have more in that range of polystyrenes but I didn't check by value. Otherwise it's going direct to the manufacturers - or using smaller resistors.

I agree ! I also found that the thicker dielectric has a nicer sound. Therefore, even if it is not necessary, I still use the ones with a higher voltage.