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Author Topic: Old Oil capacitors  (Read 3961 times)
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lu8dam
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« on: September 28, 2022, 07:30:14 PM »

Greetings to all.
Has anyone tried oil capacitors in audio frequency tube stages? Regarding polyester capacitors, hardly a difference is heard in terms of distortion. It is less with oil capacitors. What caught my attention is that this phenomenon is audible in headphones. Oil capacitors ARE NOT devalued.
The preamp vacumm tube is an EF86, and +B is 120VDC


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« Reply #1 on: September 28, 2022, 10:42:08 PM »

I use a lot of Sprague "Vitamin Q" oil caps in my audio builds.

A lot of the Russki KY- types as well, then they got expensive. Tongue

Both are PIO as far as I know.

Both are good at audio tasks.

Nothing wrong with poly caps, I use them in receiver recapping.

73 Dennis
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« Reply #2 on: September 29, 2022, 01:15:21 AM »

An audioplile sort of tube amp builder used to appear at the old surplus store and buy up all the small-value, old metal cased oil caps. He swore there was a big difference in listening when using them for interstage coupling and general decoupling, even to the point of putting a 1uF across an electrolytic filter. He got all the little 0.1 to 1uF ranges of 'bathtub' oil caps. He said the same that he could hear the difference. he also said that the oil caps were better because the innards didn't vibrate.

I can only attest that I have heard some old tubular coupling capacitors 'sing' when audio voltage was placed across them, denoting I suppose the vibration.
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« Reply #3 on: September 29, 2022, 08:38:14 AM »

The next question would be do different oils have different acoustic properties? What sounds better? Castor or Silicon? Is Castor best for Classical and Silicon best for modern music?  Don’t know if it has been used yet but maybe something like e thin grade motor oil for Country?
In theory you can install a small drain plug and filler top and have different oils for establishing a mood.
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lu8dam
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« Reply #4 on: September 29, 2022, 09:26:30 AM »

Best of all, it seems that this insignificance does not cause any effect, and yet it does.
That is what always encourages me to experiment.
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« Reply #5 on: October 04, 2022, 02:56:57 PM »

I really don't think you will hear a difference between an oil cap, a film cap, an orange drop, or an Auricap 'high resolution' brand capacitor (not picking-just an example of a costly high quality part).

It's my opinion that many audiophiles acquire notions from media (and occasional doctoral thesis) about extreme specifications for passive components. While extreme specs may be  important for cases where science is used to push performance to the limits of physics in a laboratory, they have no humanly discernable importance when placed inside of an audio reproduction system including the speakers or headphones.

If there was reliable test data, such as between two identical amplifiers with one having oil capacitors and one having film, then it might be worth looking into, but the speakers would still ruin it.

I've never seen any such data offered, either from independent double-blind listening tests or from laboratory measurement tests, but maybe others have the data and can show the results.

Not holding my breath for the science there, because all amplifier manufacturers and kit/parts sellers perform extreme marketing, pay for glowing reviews and 'laboratory tests', and the kitters encourage experimentation. This is done for one reason which is to sell more goods andespecially high profit goods.

Here's a quote: "I can tell you that the cheap caps tend to sound lifeless". Of course - because they sell expensive caps. OK fine. Those who believe they can hear the differences should experiment and be happy to please themselves in a free country.

Would I use oil caps for coupling? Yes and here is why:
I would use vintage oil caps for audio if it was a personally important piece of equipment for me to build, and then only because I have an emotional liking for them. It pleases me to use them and to see them in equipment.
My choice of oil caps would have nothing to do with the sound and any modern $2 film capacitor would be the same except in cost and appearance.
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« Reply #6 on: October 04, 2022, 03:50:06 PM »

I have a thing for Orange Drop capacitors myself, just like the way they look. Over on the bay they have orange drops especially for guitars for just four or five bucks each, or you can splurge and buy the super deluxe 920D reproduction vintage oil filled 0.047 caps for only $56 each with free shipping! Just imagine how “smooth” maybe even “oily” you would sound with a preamp and modulator running all 920D custom oil filed!  The add says that they develop vintage sound as the oil ages.

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« Reply #7 on: October 04, 2022, 05:58:03 PM »

I've done the comparison Opcom relates to.

My ears can hear a difference thru a good Altec speaker system, driven by identical mono amplifiers.

Neither one is bad (film or oil), but the oil is just sweeter to listen to.

That is, with full range music as the source.

73DG
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« Reply #8 on: October 04, 2022, 09:46:24 PM »

I have confidence in your opinion but I can't relate to 'sweeter'. I would have to do the same as you did so I could have a comparison.
It's also possible that my hearing isn't good enough to be sure of a distinction. If it can be heard it should be measurable but how?
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« Reply #9 on: October 05, 2022, 09:31:34 AM »

With an attitude like that Patrick you would never make it in the field of Broadcast Processing! Having spent years in broadcasting and having to work with Program Directors who obsess about brightness, presents, clarity, punch and energy I found that I never had a good idea what any of that means but would just crank on the knobs in the old days and eventually everything became loading different presets until we had processing that makes them happy.
General managers and often the jocks just wanted the loudest station on the dial, often to the point of driving the agc full up and limiting so much that looking at the modulation monitor it would just sit at 105% and wiggle, but I learned years ago that engineering’s job is to make certain that you can hear it but not what it sounds like. At least that was my experience.
The people with the “golden ears” have the ability to tell the difference between if you were using black, green or orange microphone cables and what sounds brightest and has the most energy is something that you cannot question, even if you can’t hear it they can.


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« Reply #10 on: October 05, 2022, 09:54:05 AM »

Greetings to all.
Has anyone tried oil capacitors in audio frequency tube stages? Regarding polyester capacitors, hardly a difference is heard in terms of distortion. It is less with oil capacitors. What caught my attention is that this phenomenon is audible in headphones. Oil capacitors ARE NOT devalued.
The preamp vacumm tube is an EF86, and +B is 120VDC

In fact you have your conclusions backwards.

A polypropylene cap measures *less distortion* than a PIO (paper in oil) or similar.

OTOH, the oil cap likely sounds nicer to your ears.
So, it's fine to use the oil cap.

Yes, audio people are known to favor oil caps because they are heard to be "sweeter", have
less "edge" and "warmer". They are not crazy.

Assuming you can still hear highs, like to 14kHz or above, it ought to be easy to hear in a
tweeter crossover, the substitution of an oil cap for whatever is in there now. Likely to be
quite radically different between an electrolytic cap and an oil cap. Noticeable between a
film cap (mylar or polypropylene) and an oil cap.

It's not voodoo. Guaranteed.

                  _-_-bear (who ran a high-end audio mfg biz)
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« Reply #11 on: October 05, 2022, 11:30:06 AM »

Don't forget that being able to discern if a tube amp is using tube rings and oxygen free cable is essential! Wink
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« Reply #12 on: October 05, 2022, 01:23:29 PM »

not to be disrespectful but can you define the terms, Sweeter, edge and Warmer?
Presents is one I always wondered about, maybe something to do with mid-range. Loudness is about the only one I have a understanding of. Maybe its like pornography, cant describe it but know it when I see it?



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« Reply #13 on: October 05, 2022, 01:33:06 PM »

Presence.

I like presents, too. Wink
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« Reply #14 on: October 10, 2022, 09:22:51 PM »

With an attitude like that Patrick you would never make it in the field of Broadcast Processing! Having spent years in broadcasting and having to work with Program Directors who obsess about brightness, presents, clarity, punch and energy I found that I never had a good idea what any of that means but would just crank on the knobs in the old days and eventually everything became loading different presets until we had processing that makes them happy.
General managers and often the jocks just wanted the loudest station on the dial, often to the point of driving the agc full up and limiting so much that looking at the modulation monitor it would just sit at 105% and wiggle, but I learned years ago that engineering’s job is to make certain that you can hear it but not what it sounds like. At least that was my experience.
The people with the “golden ears” have the ability to tell the difference between if you were using black, green or orange microphone cables and what sounds brightest and has the most energy is something that you cannot question, even if you can’t hear it they can.




One is obliged to change one's externally-expressed attitude and way of interaction depending on the paid work one wishes to do. I've always been successful in whatever electronics work I have chosen over the decades, though have never been that interested in professional broadcast station audio work, more interested in the transmitter side of things. There are reasons why it's fruitless to argue with those who prefer different colors, thicknesses, feels, etc.. of electrically identical cables. If someone is paying for it, they have the right to decide whatever they want. Why mess that up?
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« Reply #15 on: October 10, 2022, 09:39:14 PM »


A polypropylene cap measures *less distortion* than a PIO (paper in oil) or similar.

It's not voodoo. Guaranteed.

                  _-_-bear (who ran a high-end audio mfg biz)

Test equipment has changed a lot since I had access to the good stuff. What is needed to measure the distortion caused by a capacitor, and how is the DC voltage applied to it? I am thinking about at least 300-400VDC across the cap.

A very simple power amp to try this out with might be the Altec 1570B due to only a very few coupling capacitors, though it's not something to use headphones with.
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« Reply #16 on: October 11, 2022, 04:53:33 PM »

The 1570B is one of my favorite tube amps.
It's not a low distortion design, has a rather mediocre output transformer.
It is full of carbon comp resistors.
Has a marginal power supply in terms of noise and hum.

It also exhibits nasty ringing due to the feedback. Look at a square wave, you
will see.

(oh and btw, it sounds fantastic on Acoustat electrostatic speakers! Go figure!)

These and other factors tend to dictate against the probability that a difference
between an oil cap and a film cap will be terribly apparent. It might be anyhow.

Best shot, imo, is to put together a system that is extremely good in most regards,
and none too shabby in its compromises. Then sub out the caps in the tweeter xover.

What that means "extremely good" has very little to price, cost, various bogus adjectives,
look, oxygen free, or anything like that. I'd be willing to discuss it, but it is sufficient to say
that most people in the audio game A) really can't hear particularly well to begin with and B)
do not actually have an "extremely good" system, and since they can't hear very well would not
know one if they sat in front of it... (regardless of size or $$ lavished...)

                        _-_-bear, who knows more than he should about high-end audio...
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« Reply #17 on: October 11, 2022, 05:04:23 PM »

not to be disrespectful but can you define the terms, Sweeter, edge and Warmer?
Presents is one I always wondered about, maybe something to do with mid-range. Loudness is about the only one I have a understanding of. Maybe its like pornography, cant describe it but know it when I see it?

Okay.
Not to difficult to explain, I think?

Edge is the opposite of "sweeter", and sweeter is the opposite of "grain" or "grainy".

So, edge and grain refer to a physical analog of what is being heard - the sound of sandpaper
has "edge". Obviously in an ideal reproduction it would sound like it has "edge". But usually people
are trying to reproduce music and vocals, not sandpaper. Some systems would be good for reproducing
the sound of sandpaper! Unintentionally, I expect?

What the ideal hifi system wants to do is to reproduce a very "natural" sound. One that is difficult to
not confuse with the "real thing". For example the human voice (very difficult to reproduce, btw) should
sound exactly like someone is physically present. One should NOT be aware of high frequencies, or where
the sound is coming from. IF the reproduction sounds false, electronic, or "mechanical", that is what is not
wanted.

The better one's high frequency hearing is, the easier it is to discern this sort of thing.

Frankly, just about everyone who is on here is too old and has likely damaged and hurt their hearing over
time, and is no longer (if they ever could) able to distinguish these things. So, for them, and most people, in reality
none of these subtle differences *exist*. Me too, my hearing (alas) has declined as well. Sad

                                _-_-bear

Oh, yes, warmer refers to the perception of more "fullness', which could be associated with midbass. Although,
the opposite is "thin" or "thinner", which is more highs, or less midbass. Think of a good Tenor voice, one could refer
to that as a "rich" sound? If it lacks that "richness" - which should be compared to how that voice is presumed to sound
in person - then it is too "thin" and one might wish for it to be "warmer".

(this is all really a matter of the amplitude of harmonics as they are altered and so reproduced by a system, or even in the recording process)

Ideally, one should get what is on the recording, but that is a discussion for another time...
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« Reply #18 on: October 14, 2022, 09:55:17 AM »




A polypropylene cap measures *less distortion* than a PIO (paper in oil) or similar.



Do you have one or more references for this information? Someone must have done tests. I read that a Mr. Bates did some tests and published them in Audio & Electronics World, but searching there I found articles by a Mr. Bateman on the topic. I have not yet read all of it but I have not seen mention of oil capacitors in the test results. The results contain as expected the many measurable and contributory qualities that capacitors have in common.
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