50V, 63V rated Polypropylene Caps >3.3uF. Do they exist? Where/ why not?

[onanysunday]

I have been looking for some nice axial or radial potted type pp or mkp audio caps (for years) that don't go bonkers with the oversized physical dimensions that come with the standard overkill 250V, 400V+ types. I get that they are higher-voltage rated and apparently only specified for tube use.. but why exactly? I wonder what the odds would be that an audio company would ever consider doing this and offer these in a smaller voltage rating, form factor and price that more people could use in more projects where the biguns just don't fit? They would pretty much rake in the money and would have this lower voltage rated mkp market completely to themselves. I have had many, many instances over the years where I could've used these smaller, less expensive capacitors in speaker crossovers or as coupling capacitors in lower-voltage solid state circuits. With the increase in voltage rating, comes the large increase in physical size and price which is something I always find myself struggling with when trying to use these caps.

 

[Lavane]

Those voltages are fine for poly caps. However physical size can be a problem.
Have you looked at 3.3uf Wima stack film caps? They tend to be pretty small.
So are some of the radials like Panasonic. I've used Wima and the brown radial Panisonic, etc., poly caps a lot. The lower values are usually pretty small.

 

[Lavane]

PM sent

 

[onanysunday]

Yes, I've also seen the lower voltage rated polyester in 3.3 or even 4.7uF. I'm just wondering why there's no love for the lower-voltage mkp type above (let's say) 3.3uF? I would love to be able to purchase 50V, 63V rated mkp's up to about 22uF or so. It seems like at some point someone decided that only tube amps might use them and everyone else in the industry just agreed and went along with it. I'm just not sure why..

 

[onanysunday]

I'd love to see some taller, higher capacitance 50V, 63V potted radials with lead spacing around 5mm or even some shorter/ thinner mkp axials with long leads. I'd buy those in droves.

 

[Lavane]

There are also polypropylene in those smaller sizes, not just polyester. Polypropylene is a better choice. Try looking at what Partsconnexion has. I've found certain caps there I just couldn't anywhere else. They carry a lot of brands and types from inexpensive to crazy high priced.

 

[onanysunday]

Over the years, I've probably spent dozens and dozens of hours looking for them, but cannot find anything from the likes of partsexpress, mouser, digikey, partsconnexion, tedds, hificollective, tubesandmore, eBay, etc. I chatted with a tech from McIntosh today at work, and he said he can get them to install in factory product, but only when purchased in lots of 10,000 or more direct from the manfacturer. Ok, but what if one of the above parts distributors fulfilled the minimum order requirements directly from the capacitor manufacturer and then just sold them to everyone else as the sole supplier? There would still not be enough demand to justify it? I doubt it. I bet they could make a killing considering what these fancy mkp/gold/silver/oil caps can fetch. I find it hard to believe that the demand for audio-rated mkp is solely above 250V.

 

[whoaru99]

I rather doubt the (apparent) non-existence of low voltage, high capacitance films is due to tube amp influence re. higher voltages.

We need a capacitor/electrical engineer to chime in. Perhaps there is something inherent to film cap design/materials that precludes a low voltage, high capacity unit that is physically small (in relative terms). Or, perhaps it's simply there isn't enough demand outside of a niche market (that can't be completely satisfied by an electrolytic or some other type rather than film).

 

[ConradH]

There's some interesting information here- https://passive-components.eu/film-and-foil-organic-dielectric-capacitors/ It seems polyester (Mylar) films can be made thinner than polypropylene and the dielectric constant is higher. Thus, you can get smaller polyester caps. If they use very thin films, the voltage rating will be lower. It seems like thicker polypropylene films would yield higher voltage parts and certainly larger parts. See the realized dielectric strengths at the bottom of the page above. It may just be too much of a PITA to source the film and make lower voltage polypropylene caps to be worth the effort.

 

[onanysunday]

I rather doubt the (apparent) non-existence of low voltage, high capacitance films is due to tube amp influence re. higher voltages.

We need a capacitor/electrical engineer to chime in. Perhaps there is something inherent to film cap design/materials that precludes a low voltage, high capacity unit that is physically small (in relative terms). Or, perhaps it's simply there isn't enough demand outside of a niche market (that can't be completely satisfied by an electrolytic or some other type rather than film).

Like I said, Mac can get them in larger capacitance in the smaller voltage form factor when they purchase in bulk. So they (can) exist at least from a technical perspective- unless he was pulling my leg. It seems like they must exist; until you actually go searching for them that is. It’s interesting all these “audio-rated” mkp’s are only available (commercially) in the HV ratings. Too bad for me I mainly work in solid state equipment and speaker crossovers where they were clearly never intended to be used for reasons still unknown to me. In speakers, they can sound terrific and generally fit in crossovers with all the empty space inside speaker cabinets. But, we’re overpaying -badly- for what we don’t need in terms of sheer size, voltage rating and price tag. I am wondering what the logic is.. I’ve seen audio-rated mkp’s at 1,200 volts. It’s bananas. I suppose it makes sense from a bottom-line perspective. The larger they are, the more $$ they fetch, and technically the more they are able to be used in all applications (where space is of no concern). But at the same time, you’d be completely missing out on a large segment of the audio market where there is smaller available space and reduced size is needed.

 

[whoaru99]

The audio market is, IMO, literally nothing in the big picture.

If someone thought there was a dime to be made I'd expect you'd be able to buy one off the shelf rather than commit your dime to a custom order of 10000 or more.

If you think there is such demand, perhaps it presents a business opportunity for you. Call up one of the cap mfg yourself and see what it takes.

 

[onanysunday]

Very true, while supposedly ‘technically’ possible to make, it’s worth noting they don’t exist for any other application either where you could just borrow them from something else. I’ve begged DigiKey to start selling the axial “audio-rated” polypropylenes because they’d be able to offer lower pricing on them because of their sheer size and sway within the industry, which they’ve finally started to do in an extremely limited roll-out with Icel of Italy, probably just to test the waters, but I’d like to see the discounts they could provide on some of the more expensive and esoteric Mundorf, Duelund, Audyn, Jensen, Jantzen caps that everyone else is overcharging for. Those products may have some potential for a high return (in profits) and would therefore be worth carrying. I’d have to go above DK to the actual cap manufacturers to (possibly) get some results, but alas, I’m just one guy. Who else is with me and would like to see lower voltage audio mkp’s for sale, or at the minimum, more pre-existing high-voltage / high-dollar audio mkp’s available from places like digikey or mouser at reduced prices?

 

[whoaru99]

I'd guess some of those brands might not be interested in distributing their wares through a common parts megawarehouse, so to speak. They have an image to uphold, don't want to sully the brand.

 

[EastPoint]

I have polypropylene crossover capacitors rated at 250v that are custom-made for me. I will inquire about 50v caps, but honestly the 250V are cheap enough, so I would imagine the 50V would be even cheaper, so I would be making even less money. Not a whole lot of incentive there, unfortunately.

 

[onanysunday]

Most of the mkp's I'd like to try and experiment with for use in crossovers are the expensive 250V, 400V+ types I can never afford that easily fetch several hundred dollars apiece. I'm thinking if they were available in 50V, 63V versions, these silver/gold/oil types would still fetch some coin but prices would come down to earth and not be as egregiously priced as some of the larger types where the higher voltage isn't needed. I mean does it really cost Audio Note $3,400 in labor and materials to produce one correspondingly priced 3.3uF 600V Silver Foil capacitor? That’s over $1,000 per microfarad. I am thinking there has to be at least some markup in there to attract “would-be” sellers.. If there’s an industry where you can charge a lot of $$ and capitalize on something so small (in relative terms) I’m thinking expensive audio film capacitors is probably it; or at least near the top.

That said, it’s high time someone profited off this and started development of scaled-down versions of these larger voltage types. There would certainly still appear to be some profit to be had for potential sellers. Especially considering how people with lots of money have no issue throwing hundreds, if not thousands on discretionary “high-end” audio purchases. While the audio market is probably a drop in the bucket compared to some of the other industries where capacitors are used, you’d have to think the much higher price they can charge for them would offset the fact they could sell in much smaller numbers and still remain profitable.

 

[pch300]

Yeah, I've been looking for smaller sized polyester or polypropylene caps in the 5-10 uF range, and not have had any luck finding those either. The ones I find are usually >100v rating and physically large compared to the units that will it will replace. I used to be able to find these at the local electronic surplus stores. Now none of them have these parts.