Mylar film/foil caps 600V for Tweed Twin

[Diablo]

I'm thinking of building a low powered tweed twin - 5E8A, and the schematic shows three .02 mfd - 600 volt caps. I'd like to buy some mylar (polyester) film and foil axial caps, but can't seem to find a source. Sozo caps are the right material, but only rated for 400 volts. Looking at the circuit, I'm not sure why 600 volt caps are needed. Do you see a problem with using 400 volt caps? Or anyone have a source for 600 volt Mylar film and foil (not metallized film) caps?

[Daver]

The Sozo's will work just fine. If you'd rather have the extra voltage margin, you could get Mojo's Dijon caps. They're rated at 600V. All the SBE orange Drop types are 600V and film/foil construction (some polyester, some polypropelene). You could get those at Antique Electronic Supply or Mouser. Really, a metallized cap like the Mallory 150's will work great too. You could use any of these caps and build a great sounding amp.
Dave

[Diablo]

Thanks Dave.
The Mojo Dijons appear to be just what I was looking for.

[Diablo]

I just received my Mojo Dijon caps. The first thing I noticed is they are about the same size as modern metallized foil caps, and much smaller than the vintage (30-40 year old) Sprague black beauty film and foil caps. So, they must be using much thinner film and foil than the "old style" caps. Oh well.

[Daver]

Diablo,
Not that Mojo needs me to defend them, but the Mojo's are significantly larger then the Mallory 150's I have. The Mallory's are rated at 30 more volts too. You have to remember the old caps were also dipped or encapsulated in plastic or epoxy and that makes them look larger. The physical size shouldn't be a concern. How do they sound? That's the bottom line.
Dave

[Diablo]

Daver, I haven't started the build yet, so I can't say how they sound. I thought about sawing one apart and taking some measurements of the film and foil thickness, just to see how they compare to the black beauties. You're right though, sound is what counts.

[Enzo]

Modern materials are far advanced over those of 30 years ago. Caps are smaller. The size tells us nothing.

[Rhodesplyr]

I like the Mojo Dijon capacitors, but I tested some in my impedance bridge while choosing capacitors for a Super Reverb repair and found the dissipation factor unaccountably low (by a factor of ten) for a polyester capacitor. I've tested enough in my bridge to know what readings I should get (including some 225P). They tested like polypropylene. So I called Mojotone, and they confirmed without any argument that, yes, they are *polypropylene* film & foil. If you look at Mojo's website, you'll notice that they never (as far as I can tell) directly state what the dielectric is; they let the reader assume that Dijon = mustard = polyester. Other sellers take this hint and advertise them as polyester when they aren't.

Thus, I think the SBE 225P or 6SPS are about the only widely available choices in a 600V true film & foil polyester capacitor these days, unless some of the boutique caps are what they claim to be.

But especially for the price, I have a favorable opinion of the Dijons. They have nice copper leads long enough for point to point construction, low DF, and are usually within 3% of their rated capacitance. To my ears, they have the clear, neutral character I usually expect from polypropylene.

[J M Fahey]

found the dissipation factor unaccountably low (by a factor of ten)

So what's the problem?
Besides that, I think that any modern 400V stands more voltage on the long run, than an old paper-in-oil "600V" one.
They *had* to over rate by a long way to achieve long service life; today we are much more consistent.

[tmod]

Thus, I think the SBE 225P or 6SPS are about the only widely available choices in a 600V true film & foil polyester capacitor these days, unless some of the boutique caps are what they claim to be.

According to Mouser there are several polyester options over 400V. I doubt all are mislabeled: Polyester Film Capacitors


Some are rather expensive though...

[Rhodesplyr]

According to Mouser there are several polyester options over 400V. I doubt all are mislabeled

I use Mouser all the time. The strange thing about their "polyester film" category is that, if you look at the datasheets, 99% of them are metallized polyester, not film & foil. Now, I'm not saying that I have any particular gripe with metallized film capacitors, but that's what Diablo was asking about :-)

[tmod]

I use Mouser all the time. The strange thing about their "polyester film" category is that, if you look at the datasheets, 99% of them are metallized polyester, not film & foil. Now, I'm not saying that I have any particular gripe with metallized film capacitors, but that's what Diablo was asking about :-)

Yeah, I know they get it wrong quite often. Over at ax84.com where I usually hang around there was this huge debacle some months ago when someone had specified 1200v schottky diodes for rectifiers ina build. Turned out someone had spotted cheap ultra fast diodes at mouser that were categorized as schottkys. Caused much head-scratching.

I just figured (maybe erroneously) that at least SOME of all those capacitors must be what their sold as...

[guitician]

Astron remakes

These say that the voltage rating is 600v, but marked 400v for the vintage look??

Vintage Tone - Red Capacitors

Haven't tried them, but the look is appealing.

[J M Fahey]

Well, at least this guy is honest.
He recognizes that Mojo lies more on looks and "perceived" advantages than on performance, yet he also cares to offer a good product, specwise.

[guitician]

What is "Mojo"

Surely it is nothing you can hear.