Testing non-electrolytic caps to find the "shielded" end

[Enzo]

RG, HL Menken sits in the rest room at work, in a small book of a collection of "best of" by he. I find it soothing to read some of his stuff while I ... relax.

[R.G.]

The tube ceramic is a "near superconductor" which forms Cooper pairs at room temp

A little - very little! - thought would show that if this statement is true, then Bybee is dramatically UNDER valuing his widget.

Anything that even marginally gets better conduction, let alone being a "near superconductor", would instantly transform the electrical power and motors industry, making Bybee richer than Walton or Gates. The claimed property of combing noise out of electrons is trivial compared to the power saved.

The mere fact that he's still trying to get thousands of dollars at a time out of his "device" instead of billions is proof that he's lying. Even if he's not motivated by money and just wants to improve audio, someone would take a "near superconductor" away from him and transform the power industry for the billions.

Economic laws can be used for reasoning, too.

[Leo_Gnardo]

RG, HL Menken sits in the rest room at work, in a small book of a collection of "best of" by he. I find it soothing to read some of his stuff while I ... relax.

Should you tire of Mencken, find a copy of the less well known Mackay "Extraordinary Popular Delusions and the Madness of Crowds." This also may help "move things along."

Recommended for everyone! Whether you're on the pot - or not!

- - - - - - - - - - - - - - -

Too bad we don't have one of these ionic purolators to dissect. Bet you half a donut that so called ceramic doesn't conduct at all.

Amazing, the hi fi wackos will pay $200 to $4000 per AC cable, try to minimize resistance in the AC supply line all the way back to the generator if they could, then stick a $440 resistor between the AC line and their component. Put 'em on your speakers too? What about conserving that precious high damping factor? Those multithousand dollar firehose size OFHC five-nines pure speaker cables, gold connectors, then a resistor? What folly. I'll take my electrons the old fashioned way, loosely organized without any quantum interference.

[Mike Sulzer]

What about conserving that precious high damping factor?

Indeed, we all know that reducing the amplifier output impedance from .002 to .001 ohms makes a huge difference when the speaker has a 7.5 ohm resistance. What could be more obvious?

[trem]

Every amp forum has this same discussion on a regular basis.

In all my years, the only place I have ever seen it matter was places like RF circuits and a pentode screen bypass needed to be "right".

It is easy to find which lead is outer foil, but as RG points out, all that means is which side of the double strip wound up on the outside after rolling.

FWIW.....I am the "author" () of the link in post #6.
My experience (again...FWIW) jibes with Enzo's wisdom. Other than identifying which end of a tubular/wrapped/rolled cap is connected to the outside foil, I have never been able to hear (or find anybody that could prove) it makes any difference in a guitar amp.

[Enzo]

A true believer might point out that grasping the cap in your fingers might introduce some hum. Of course for that to matter, the amp would nee to be operated with people grasping caps with their fingers.

[Leo_Gnardo]

Perhaps someone, somewhere, has built two near-identical amps. One with all the film caps oriented correctly, the other with all of them "backwards." Everything else, identical. Then set up a double blind test, see if the player/listener can tell the difference.

Anyone hear of such a thing being done? Please tell us about it.

Something nice about MEF, not much chance of being thrown out for mentioning double blind test. Some places, that's the cue for ejection. "We want to believe..."

[Diablo]

I was just wandering around YouTube today and found this fellow’s method of finding the outside shield on non polarized caps. I was getting worried that I built all my amps wrong because I never paid attention to the cap orientation. I don’t even own an oscilloscope to figure out the orientation. Glad I did a search on MEF and found this thread to ease my worries. I think I followed the discussion years ago, but I forgot the conclusion that orientation doesn’t matter.

[Chuck H]

I wouldn't say it doesn't matter. But I might say that if it matters more than one or two percent noise floor when applied to typical tube amp topology that I'd be surprised.

I've done experiments with different dielectric materials and heard more difference than I did with capacitor orientation (yes I measured actual capacitance values). I haven't built a lot of amps, maybe ten that are with customers and a couple that I own. Well, plus countless rebuilds and mods. But the point is that I did, indeed, look for differences and have decided not to trouble about capacitor orientation. What's funny is that this stuff will stick in your head and get to you. So when I was building with caps that were marked (which I don't anymore) I actually would orient the marked side to the lowest impedance. Because why not? But as I said, the caps I use now are not marked and I don't care. Nor have I noticed a difference or had any anomalies in noise or performance as far as I can tell.

BTW... I'm using polyester caps now where I use to use polypropylene. My reasoning was that poly polypropylene has better thermal stability and I didn't want my amps to sound different in the first set than on the last set. I had heard a difference in a production amp that had polyester caps after switching them out and was convinced because when I changed them the problem went away. Well... Those must have been particularly crappy caps because I'm not having any trouble with the polyester caps I'm using now (Panasonic on the last build). I switched back to polyester because the Sprague orange drop 715p's that I was using became INSULTINGLY expensive. Same with Sprague Atom filters. But that's a different story that I've already told here and there on the forum.

I'm picky. I'm listening. There's no significant difference with orientation or dielectric as it applies to tube guitar amps. But, as noted above WRT my initial experiences, do buy quality, respected parts. Cheap parts can exhibit all kinds of anomalous behaviors that may or may not be related to the questions at hand. Some will say a cheap cap is as good as an expensive one and all caps sound the same. This is NOT my experience. But when quality brands and products are involved the gap becomes insignificant to my perceptions.

[Helmholtz]

My reasoning was that poly polypropylene has better thermal stability

PP capacitors have less temperature dependence of capacitance but often lower max. operating temperatures than polyester types.
Electrical data of PP types is generally superior which doesn't mean they "sound better".

[Diablo]

Can someone explain the mechanism that a cap would become noisy over time? My 5E8A tweed twin clone recently got noisy/hum on channel 2. I traced the problem to the silver mica bright cap on the volume pot. I could wave my hand 6 inches from the pot and hear the hum get louder. I replaced the cap with a new silver mica and the hum vanished. The bad cap still tested fine at 100 pF.

[R.G.]

It's developed internal or external leakage. Note that you also redid the solder joints on the ends of the cap leads, and if one of those was a cold joint, it could have become noisy as well.

[Helmholtz]

Can someone explain the mechanism that a cap would become noisy over time? My 5E8A tweed twin clone recently got noisy/hum on channel 2. I traced the problem to the silver mica bright cap on the volume pot. I could wave my hand 6 inches from the pot and hear the hum get louder. I replaced the cap with a new silver mica and the hum vanished. The bad cap still tested fine at 100 pF.

It is not quite clear what you mean with noisy. Leaky or cracked caps can produce differend kinds of noise but they do not by themselves generate hum.

But like any conductive surface connected to a sensitive circuit point, a cap can act as an antenna to local hum fields. (Seems your body/hand was at least one of the hum sources.)

Hum intensity will depend on existing hum fields, cap size, cap position/orientation, closeness to grounded parts like pot casing or chassis.

I can't think of a way deterioration of a bright cap could increase low frequency hum sensitivity.

Does your amp have a "ground plane" like a metal mesh or foil that covers the chassis producing a closed Faraday cage?

[g1]

Can someone explain the mechanism that a cap would become noisy over time? My 5E8A tweed twin clone recently got noisy/hum on channel 2. I traced the problem to the silver mica bright cap on the volume pot. I could wave my hand 6 inches from the pot and hear the hum get louder. I replaced the cap with a new silver mica and the hum vanished. The bad cap still tested fine at 100 pF.

If not 'silver-mica disease', this is an interesting read anyway: https://www.antiqueradios.com/forums...ic.php?t=61153

[Diablo]

It's developed internal or external leakage. Note that you also redid the solder joints on the ends of the cap leads, and if one of those was a cold joint, it could have become noisy as well.

I can rule out a cold solder joint because I’m overly careful with soldering, use heat sinks on every component so I don’t damage any, inspect the joint for good flow and then measure resistance across the joint. I’m a metallurgist too.