Axial leaded PP film foil capacitors

[bepone]

this Kemet A72 proposal was actually in the past Arcotronics brand from Italy, Arcotronics series 1.72 KP.. guitar values are still available on ebay

[kuDo]

I do understand the concept of interior-wiring-as-sculpture, where the appearance is the thing. And I do appreciate tidy wiring. But to me, these are a means to an end, the sound that comes out. My preferences don't extend to the look of components, given that they are the right values and mounted correctly for the part's health. I'm also not much given to modding for modding's sake, so ease of modification isn't something I put a lot of emphasis on. In my mind, you design (or choose for copying) a schematic, do a prototype and do adjustments to the circuit, then build a solid, stable "production" version to last a long time in full use. So I have a different viewpoint.

Randall does have some valid points about capacitor dielectric materials. However, whether a particular style of cap (i.e. film and foil vs. metalized film) is more appropriate at a given point in a circuit depends on the voltages and currents at that point in the circuit. As a for-instance, whether the low ESR of film-and-foil makes a difference over metalized film depends on the necessary frequencies to be passed and the amount of AC current that passes. ESR and ESL effects can be calculated; their effect on the signal passed can be calculated too. Interstage coupling caps have very, very small currents to be passed through the caps, so I personally would do a lot of calculation on the signal effects before spending a very large amount of money on F&F caps over MF. In a speaker crossover, there are quite large currents flowing, so F&F may well be an advantage.

Artists should use the finest paints, bronze, and marble that their artwork demands and they can afford, of course. But my experience is that I don't show the inside wiring of my amp to the audience.

That is nicely put!

I am relatively new to the game and there are a lot of subjects that I stil need to shine a light on to form an opinion.
Selecting components based on solid arguments beeing one of them.

I like the motivations of Aiken regarding his choise of caps. So I was investigating if It would be easy and practical to adopt it to my designs.
Every design I build must be better than the one that preceded it logically, as a result of new learnings. A lot of the time I still think of my builds as a rat’s nests so I do want to approve on that side as well. So one and one seem to meet in Aikens ideas. Axial caps with the right specs.

I am guilty to at least a little of wanting to build the interior-wiring-as-a-sculpture. My day time job as a CGI artist has made me a very eyes first kind of guy. As oppose to specific parts from a specific brand isn’t that important to me, because my hearing is reasonable at best due to the decibel onslaught of previous years, so I doubt I would hear the differences.
I do however like to choose a component based upon the idea it will last en during it’s life it will sort of remain within it’s value boundaries to fulfill it’s intended job and doesn’t drift to much due to heat or age.

Thanks so far for all your input. This forum has been kind en responsive to me!

[R.G.]

That makes sense, pdf. Temp stability DOES matter when the caps are being baked inside an amp.

[kuDo]

I suppose that as temperature stability is the actual motivation for seeking film foil caps here, kuDo could try searching for axiel caps (which may be a metallised type) that have a very low temperature coefficient, rather than a generic search for film foil per se (which probably have a low temperature coefficient).

That would indeed be a good idea, since the axial PP film foil caps I to date have found and are available to are few.
So far: the Michicon build ICEL pws caps.
https://nl.mouser.com/ProductDetail/Nic ... RtlA%3D%3D

The metallized axial caps have a pretty good availability so maybe I need to head in that direction an look for good heat stability.

Found a nice little piece that summed it up nice to me:

Polyester film (PE) Capacitors : with higher dissipation factors (tan δ) are generally suitable for low frequency operation, at a comparatively wide range of temperature. The relatively high dielectric constant (ε ) makes it is possible to produce large C-Values in small dimensions.

Polypropylene film (PP) Capacitors : with very low dissipation factors (tan δ) and high dielectric strength and high insulation resistance. They are suitable for high voltage, high frequncies and large current circuits, have are larger dimensions and negative temperature coefficient.

Polycarbonate film (PC) Capacitors : the dielectric constant (ε )are just between polyester and polypropylene materials, additional advantages are excellent temperature stability and good long term stability.

polystyrene film (PS) Capacitors : with excellent high frequencies and high insulation resistance, very low dissipation factors (tan δ) and low capacitance tolerances, the heat resistances and solvent resistance factors are lower.

No real mention of film foil vs metalized in this but at leas a nice writeup on the plastics.

[kuDo]

Arghh something went pear shaped…. I edited this post. This reply can be removed

[R.G.]

@kuDo
That makes sense. I'm a technician, not an artist, but I do appreciate art when I see/hear it. Go for what makes your aesthetic sense happy.

Here's some techie info that might help. I went to wikipedia for the temperature coefficient of PP and other film caps, and found this:
https://en.wikipedia.org/wiki/Film_capa ... te_note-62
... which is a good intro to the tech aspects of film caps. The nice paired charts of temperature and frequency variations of the kinds of insulation led me to this reference from Vishay/Roderstein:
http://www.vishay.com/docs/26033/gentecin.pdf
... and that one is a good general introduction to the tech considerations of non-polarized caps in general and film caps in particular. It led me to this thought. The chart for capacitor change with temperature shows that polypropylene and polycarbonate have similar but OPPOSITE temperature changes. That means that one could concoct a nearly zero temperature drift capacitor by paralleling a polypro and a polycarb cap of nearly equal value. The combination would have a net capacitance drift much smaller than either half alone.

The interior winding and lead termination scheme has a huge effect on cap performance. Tinkering with where and how and how much the leads connect to the internal conductive metal strongly affects the ESR and ESL "impurities" of the finished cap.

The devil is always in the details...

[kuDo]

@kuDo
That makes sense. I'm a technician, not an artist, but I do appreciate art when I see/hear it. Go for what makes your aesthetic sense happy.

Here's some techie info that might help. I went to wikipedia for the temperature coefficient of PP and other film caps, and found this:
https://en.wikipedia.org/wiki/Film_capa ... te_note-62
... which is a good intro to the tech aspects of film caps. The nice paired charts of temperature and frequency variations of the kinds of insulation led me to this reference from Vishay/Roderstein:
http://www.vishay.com/docs/26033/gentecin.pdf
... and that one is a good general introduction to the tech considerations of non-polarized caps in general and film caps in particular. It led me to this thought. The chart for capacitor change with temperature shows that polypropylene and polycarbonate have similar but OPPOSITE temperature changes. That means that one could concoct a nearly zero temperature drift capacitor by paralleling a polypro and a polycarb cap of nearly equal value. The combination would have a net capacitance drift much smaller than either half alone.

The interior winding and lead termination scheme has a huge effect on cap performance. Tinkering with where and how and how much the leads connect to the internal conductive metal strongly affects the ESR and ESL "impurities" of the finished cap.

The devil is always in the details...

That’s a nice deduction! Great. You might not be an artist, but you are pretty creative as a technician.

Don’t know if this would have some cons but is seems like a good idea. You can then half the value per cap.

Thanks for the links, I’ll take a peek there

[pdf64]

I think Zollman may have looked into this, he has with most stuff from strings to speakers.

[kuDo]

I think Zollman may have looked into this, he has with most stuff from strings to speakers.

Oke, time for an educational moment. Who is Zollman? @pdf64

[pdf64]

Sorry, Zollner, see https://www.gitec-forum-eng.de/the-book/
If you can read German, the hardcopy would seem to be well worth buying.

[bepone]

Polyester film (PE) Capacitors :

ok for everywhere

Polypropylene film (PP) Capacitors :

ok, mix with care with poliester

Polycarbonate film (PC) Capacitors :

forget about, iritant cap, not ok highs

polystyrene film (PS) Capacitors :

forget about / for Hifi RIAA circuits or in Hifi NFB circuits and thats it

[pdf64]

I’ve been using LCR’s polystyrene caps for decades, they’re excellent.
If shootouts are your thing https://youtu.be/ifC2A5QkbRY

[bepone]

my recomendation always, who is interested in caps need to buy the same value caps or set for guitar amp use, but with different material, series or shape..
make amp which alows quick change (like PCB opposite mount, soldering fast from the copper/thinned size) , and in a few min one can change complete set or only few caps.. it is easy and fast to find proper combination for everybody.. tone is changing from irritant to mellow.. if one can't hear any audible change, can quit with this hobby and start to do something else..

[pdf64]

my recomendation always.. if one can't hear any audible change, can quit with this hobby and start to do something else..

Thanks for the kind advice, but after 4 decades I still rather enjoy tinkering with this stuff, so I'll stick with it.
I'll leave will-o'-the-wisp chasing to others though

[R.G.]

my recomendation always, who is interested in caps need to buy the same value caps or set for guitar amp use, but with different material, series or shape..
make amp which alows quick change (like PCB opposite mount, soldering fast from the copper/thinned size) , and in a few min one can change complete set or only few caps.. it is easy and fast to find proper combination for everybody.. tone is changing from irritant to mellow.. if one can't hear any audible change, can quit with this hobby and start to do something else..

The general idea of isolating changes and making only one change at a time is a good one. The problem is how do you measure change?

Guitar amp makers are not the first ones to go on and on about the delicate shades of "tone" obtained from different components. The high fidelity world went through several decades with supposed "golden ear" listeners deciding things like music is too grating to listen to if it was even ONE time run through a wire that was not oxygen free high conductivity copper, or that silver plated hookup wire preserved the "sound stage" and the "air between the notes". Only trouble was that listening tests designed to be fair and free of listener bias or commercial leanings showed that the magic listeners could not even pick between the magic parts and ordinary stuff as well as by chance alone. In fact, many of the golden ears did >worse< than random chance at picking between magic parts and ordinary stuff purely by listening. The hifi world has since refused to submit to tests that could expose the emperor's new clothes.

Humans can not in general remember "tone" accurately enough or long enough to be usable at quick interviews of sound equipment. It is a quirk of human psychology that humans do >think< that they can do so, and are certain enough of this to argue the point even after well designed and fair tests prove them wrong.

I personally know people who claim to hear a difference in tone if a single resistor in a guitar amp is swapped end for end. We agree to disagree, and I don't push the issue hard enough to break the relationship. But neither of these people will let me swap or not swap the resistor ends where they cannot see what I'm doing and then try to consistently tell me which is which.

If a listening test for component combinations makes you happy with the sound, by all means do it and find one you like. But if you do, don't ever participate in a blind or double blind test of your choices. You won't be happy.