Axial leaded PP film foil capacitors

[kuDo]

Hello everyone,

Where can get axial leaded Polypropylene film foil capacitors (not metalized ones)?

As far I can see, they seem to be really scarce.
I can only find the Nichicon PWS range. Can someone show me where to find some?


I am currently reading on the website aikenamps.com made by mr Randall Aiken.
On it he explains the question; “ Why do you recommend polypropylene film/foil capacitors?”

To which he answered:
“ Because they are the best, in terms of temperature stability, and, subjectively, tone. The interior of a guitar amplifier chassis tends to get very hot, particularly in a combo, where the tubes are hanging upside down beneath the chassis and the heat rises upward. Polyester and metallized film capacitors have very poor temperature characteristics compared to polypropylene film/foil, which means the amplifier tone will change as the amplifier heats up. A 5% or 10% drift in value can produce a very noticeable shift in tone, depending upon how the capacitor is used in the circuit, and all caps will drift in the same direction, which is determined by the characteristics of the dielectric material, so the effect is multiplied. Also, polypropylene capacitors are far better in terms of dissipation factor and dielectric absorption, which some people say makes them sound better. I use them because they have the best characteristics, even though they cost quite a bit more than the cheaper polyester caps. The long-term temperature stability and quality construction makes them worth it, in my opinion. The most commonly used coupling cap, the Sprague Orange Drop, is available in polypropylene film/foil, but only in a radial-lead package. These are fine for PC board amplifiers, but some manufacturers use them for point-to-point boards by bending the leads out at the body of the capacitor. This usually leads to cracking of the epoxy seal around the lead entry points, which can allow moisture into the capacitor, leading to drift and potential failure. I use only axial-leaded capacitors, because they are designed for point-to-point style mounting, and the epoxy end seals do not crack when they are mounted on the board.”

[R.G.]

Here's a thought experiment. The objection to radial polypropylene film-and-foil caps seems to be that the leads are short and not going in the right directions. What would happen if you formed a tiny loop in a length of wire, and soldered that over the short lead stubs of a radial PP F&F cap?
Sure it would look a bit odd, but it does seem to satisfy the complaint.

As for me, I'm still searching for polystyrene-and-gold-foil caps for my amps...

[kuDo]

Here's a thought experiment. The objection to radial polypropylene film-and-foil caps seems to be that the leads are short and not going in the right directions. What would happen if you formed a tiny loop in a length of wire, and soldered that over the short lead stubs of a radial PP F&F cap?
Sure it would look a bit odd, but it does seem to satisfy the complaint.

Hello R G,

That is indeed a possibility, I was just curious were I could find stated capacitors. I can not really find them and mr Aiken says he uses them.

If I take a look at his older amps I see a lot of yellow axial caps (not cabs ). The pictures I can find are never sharp enough to get a clear reading of the used capacitors. I was trying to learn something from a amp builder I think can teach me a thing or two.

As for me, I'm still searching for polystyrene-and-gold-foil caps for my amps...

Maybe they are only available when the moon is full

[sluckey]

AES has several brands to choose from. Here are some yellow ones...

https://www.tubesandmore.com/products/c ... xial-leads

[kuDo]

AES has several brands to choose from. Here are some yellow ones...

https://www.tubesandmore.com/products/c ... xial-leads

Hello Sluckey,

I have seen those, but they are of the metallized film variety, not film foil.

It seems impossible.

[martin manning]

Here's one: https://content.kemet.com/datasheets/KE ... _AXIAL.pdf

[kuDo]

Here's one: https://content.kemet.com/datasheets/KE ... _AXIAL.pdf

Hi Martin,

Great find!

What if you would commit to this kind of capacitor throughout your build? What if you need a 1uF or 10uF for a kathode bypass?
The range doesn’t support them.
I also noticed that the caps change to metallized film once you pick the ones rated for 630V.

But it is an option, so maybe this is possible like Aiken states.

[pdf64]

LCR make excellent caps http://lcrcapacitors.co.uk/wp-content/uploads/fpc.pdf

[kuDo]

LCR make excellent caps http://lcrcapacitors.co.uk/wp-content/uploads/fpc.pdf

Thank you sir,

That is indeed a nice contender. Very temperature stable so it seems.

For the higher values I mentioned above size will become a factor.

[gktamps]

Metallized PP has certain qualities that are preferred in some situations, among them, self-healing properties.

Regarding damaging radial caps like orange drops by bending the leads, if you use a bending jig, or small pliers as I do, at the base of the cap and then bend the lead, there should be no problem. It also helps to tack the cap down to the board so it's not suspended by the leads, putting pressure/tension on where they enter the cap. There have been billions of these caps used in electronic equipment, and surely millions in guitar amps, but what is the reported failure rate from cracked potting?

[kuDo]

Metallized PP has certain qualities that are preferred in some situations, among them, self-healing properties.

Regarding damaging radial caps like orange drops by bending the leads, if you use a bending jig, or small pliers as I do, at the base of the cap and then bend the lead, there should be no problem. It also helps to tack the cap down to the board so it's not suspended by the leads, putting pressure/tension on where they enter the cap. There have been billions of these caps used in electronic equipment, and surely millions in guitar amps, but what is the reported failure rate from cracked potting?

All good points,

I was merely looking for the axial PP film foil caps that mr Aiken was referring to.
Since I could not find many I thought Maybe I was missing out on something. So I asked here hoping someone could enlighten me.

I have been using those radial caps as well. At some point they do get rather big to be flopping in the breeze between those turrets.

I have to say I do really like how Aiken builds his amps.

[TUBEDUDE]

I gave up looking decades ago and settled on Sprague 716P foil/pp caps. For all power supply, and cathode capacitor needs I use Metalized foil.
The needle nose as bending guide and spaghetti tubing/heat shrink covered leads are fine. Ĺarger sizes will need stabilizing.

[kuDo]

I gave up looking decades ago and settled on Sprague 716P foil/pp caps. For all power supply, and cathode capacitor needs I use Metalized foil.
The needle nose as bending guide and spaghetti tubing/heat shrink covered leads are fine. Ĺarger sizes will need stabilizing.

I have been using the 715P en 716P Spragues as well. They are nice for the job, but I would like to use some axial caps that are similar.
But I don’t think it won’t be the same as the Spragues. They do stick out like a sore thumb.

[R.G.]

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.

EDIT: After that blast, it's true confessions time. I do have a little of the wiring-as-art in me. I learned to use lacing tape to bind and bundle wiring, and I like it a lot. But this is mostly inappropriate for the insides of amps as the high voltages and high impedance of the signals mean that bundling increases crosstalk and signal coupling problems.

[pdf64]

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).