heres an odd one

[bob p]

I used the Enzo rule even then. If you are taking a cap out. Most of the time you just replace it. Your time is more valuable than the component.

That's a REALLY good rule to follow for small/inexpensive caps -- once they're out, it's a waste of time putting them back in and you're best off by just replacing them. Where meters really do help is in deciding which cap to take out (assuming that the circuit allows you to perform a useful in-circuit test. Sometimes you may have to lift one leg to get the answer. Sometimes that's better than removing the cap.).

Being constrained by time, I'll replace any low voltage cap if there's ever a reason to take it out, but I'll avoid replacing something like an inverter grade PSU cap unless I can prove that there's a reason to replace it.

I think that a low-voltage ESR test will give you useful information more often than not.

[loudthud]

About a week ago for the first time I heard the ripple modulation if a clipped guitar note. Now I can't unhear it.

[jamesmafyew]

Well, look at #2 in my post. If you are even somewhat skeptical about my ability to hear things like this, how do you explain the things i don't hear? Why no placebo effect there? theres really only one answer to that ! Everything is relative. If someone tells you you are using too much treble at one of your gigs and accuses you of having hearing damage, that makes no sense to me. Why? Because i am listening to all the other instruments too and I'm going to adjust my tone accordingly. If i crank the treble i would notice MY tone is much brighter than thiers. Again, everything is relative. I'm not tech, and i have no doubt i'm looked at here as an idiot because i know so little about electronics on the technical side. But ears have nothing to do with that. For all you know i may have ears that would make the proverbial EJ ears look tone deaf. No offense at all, just sayin...

I think the problem here is assigning causation to one particular (and very small) change, when there are a number of other, unaccounted variables in play that aren't acknowledged. One of the reasons quantified measurements are helpful is that they tell me, for example, that the dimensions of my cab and the dimensions of my room have an effect on sound orders of magnitude greater than my choice of components. For example, sometimes I tweak a value of a component in a circuit I'm prototyping. I listen to it and I think it makes a huge difference. But then often I'll mount that component-change to a switch so I can toggle back and forth on the fly. Then I find out that it's not really different at all --- what was different is that I'm playing the amp in a different part of the room and the angle between the speaker axis and my ears is different. Point is, sometimes we hear difference because there IS difference, but it's not the difference we think it is, it's caused by something we haven't accounted for. Then other times, we don't hear difference because the difference is in fact inaudible. Notice that none of this has to do with the quality of anybody's ears, or their particular tastes -- only the failure to account for ALL variables in the situation.

And all of that is just to try to establish correlation between thing A and thing B. But correlation isn't causation! Proving causation is much much harder to do.

[soundguruman]

Now this is my idea of silly:
Only $113 a pair...
But another thing you guys don't measure is the microphonics of the capacitor.
Like for example, orange drops, used as coupling caps, are quite microphonic. (go ahead, give it a tap tap while it's ON.)

When the chassis of the amp vibrates, so do the capacitors, and you are getting quite a lot of harmonic influx, just from the capacitors vibrating...or you can call it intermodulation...
this is part of why capacitors add their own sound to the amplifier. There are several other characteristics we never measure also.

Anyhow, despite the fact that these caps are microphonic as Fudd, the guitar players love them and insist they add major mojo to the sound.
I actually think they sound quite good also, compared to the Fender stock capacitors, in recent models.

[Chuck H]

But another thing you guys don't measure is the microphonics of the capacitor.
Like for example, orange drops, used as coupling caps, are quite microphonic. (go ahead, give it a tap tap while it's ON.)

That only works if you can isolate the tubes and caps entirely. Which you can't. What your most likely hearing is the vibration of the tap affecting the first preamp tube.

[R.G.]

Anti-microphonics trick: go to auto parts store, buy a tube of high temperature gasket gook, which is a high temperature silicon rubber that can be used on engine heads, up to about 500F. Goop some of this on the parts you want to be non-microphonic and let it cure. It's not perfect, but it's more dissipative than the hard glass and metal parts, and will damp a lot of microphonics.

Capacitor microphonics can indeed be a big deal, and it's dependent not only on the cap, but also the speakers, speaker bolt tightening, gluing of the enclosure, any damping materials, chassis bolt tightening, wire, dress - it goes on and on, anything that affects the transmission of sound from the speakers to the capacitor, which is also a microphone, and everthing in the path is resonant at some frequency or other.

This can also be why one tube sounds different from another, BTW. Resonances in the glass+metal setups holding the electrodes.

[R.G.]

But another thing you guys don't measure is the microphonics of the capacitor.
Like for example, orange drops, used as coupling caps, are quite microphonic. (go ahead, give it a tap tap while it's ON.)
When the chassis of the amp vibrates, so do the capacitors, and you are getting quite a lot of harmonic influx, just from the capacitors vibrating...or you can call it intermodulation...
this is part of why capacitors add their own sound to the amplifier. There are several other characteristics we never measure also.

Thank you for backing off the "ear is so good you can't measure it" malarkey. It's refreshing to see some real technical content and a pointer to a real - and measurable, if not often measured, physical effect.

[soundguruman]

That only works if you can isolate the tubes and caps entirely. Which you can't. What your most likely hearing is the vibration of the tap affecting the first preamp tube.

There is no question that tubes also are microphonic, or at least the circuits we use them in promote microphonics.
Nope, it's the capacitors, try it yourself.
When a note is played, the circuit board vibrates from the speaker, and re-introduces that note back into the audio path thru the microphonic capacitor.
It causes intermodulation if you will, "distortion."...
That's part of what makes it sound the way it does...
As a matter fact, that's only one of the many, many, many things that we never pay the slightest attention to.

Somebody thought of oil filled paper metal capacitors to "dampen" that vibration and isolate the component from being affected by vibrations. Or to soften the affect.
We would think of the oils as dielectric. But that was not the only intention. It was also to make the cap less microphonic.
And you can see, that a well constructed oil filled cap is far less microphonic than it's solid constructed counterpart. - try it.

At first, people cried that the oil was toxic. Now the caps are made with vegetable oil.

[soundguruman]

Thank you for backing off the "ear is so good you can't measure it" malarkey. It's refreshing to see some real technical content and a pointer to a real - and measurable, if not often measured, physical effect.

Your brain with ears attached is finer than any test equipment or computer ever made. I do not back off.
Stop giving so much credit to machines. The machines are only extensions of your own senses.

[daz]

Your brain with ears attached is finer than any test equipment or computer ever made. I do not back off.
Stop giving so much credit to machines. The machines are only extensions of your own senses.

It's really quite simple i think....each is better in a different way. I think what you are trying to say, and i believe this to be true, is that in the case of audio electronics, everything used to test, measure, calculate, etc etc etc, are all nothing more than a means to an end, and that end is to please the ear. And much of those measurements and all cannot tell you how they will effect what you hear, good or bad. Therefore the ear is the final judge and the only thing that matters in the end. What the others are arguing is that the tech side can determine things the ear cannot. But in the end you are correct in that the ear is the final judge because it is that which you are ultimately trying to please. I think you're both right in what you are trying to say, but you are both looking at it from different perspectives. I go by the ear for the most part because thats what i know. I only know enough electronics theory to know how to build and amp and from there my ear takes over and with what little i know i am able to find my way to good tone like a blind person uses sound to find thier way.

[Enzo]

Guruman is trying to confuse a philosophical point and a technological point. You ears are not measuring devices, they are transducers. You cannot provide any measurements your ears ever made, all you can provide is a description of the experience they gave you. Are they exquisitely sensitive aural pickups? Of course they are. But this isn't man versus machine. The argument is whether or not we can measure things that our ears can hear. The argument is not whether machines are better than ears.

We have sensing equipment that can sense the footfalls of an insect, our ears can never come close. We have scales that can weigh single molecules, nothing in a human body can remotely come close. We can detect temperature changes of millionths of a degree, and they can do that from just about absolute zero up to the temperature of nuclear fusion, the human body cannot come remotely close to that. We have instruments that can measure anything the body can sense, and do it orders of magnitude better. To claim otherwise is to cling to some sort of romantic notion of human perfection.

There may be things we do not yet know how to properly measure, or we may not have a good idea how to put measurements into a meaningful context, but that is not at all the same thing as being not measurable.

[R.G.]

Your brain with ears attached is finer than any test equipment or computer ever made.

I like to think that MY ears and brain are the finest things ever, too. Well, there was this girl in high school, but that's another story.

Think about Lord Kelvin's quote. I put it here for you to think about. Your ears and brain cannot come up with any repeatable measurements.

Let me repeat that. Your ears and brain cannot do repeatable measurements. Your ears and brain cannot put things in numbers. Period.

Your brain can dig signals out of noise better than anything else we've ever found. [I note here that it's better in real time, although there are some computer applications that can do a better job, given enough time. Someday, the computers will get enough horsepower do better us in real time on general purpose applications.]

It has also been demonstrated to flatly make up signals where there are none. Worse yet, the brain has been found to delude itself, seeing and hearing things that are not there, and also making little slips of both perception and veracity to suit the personal ambitions of the owner. Measurement devices do not do self delusion. That is an unbelievable advantage in some cases.

The ears plus brain are indicators. They are not measurement devices. That's a fundamental difference you're missing.
The brain *invented* measurement devices to make up this lack itself. As you yourself say:

The machines are only extensions of your own senses.

Yes, they are. They do things for us that our senses cannot. Can your ears and brain tell you how much intermodulation distortion (to use a term you seem to be fond of) is in a sound? In either percent or db from a reference? Can it tell you the frequencies being intermodulated?

It seems that you are incapable of perceiving this difference. That's too bad.

I do not back off.

I'm sorry for you. Willful refusal to consider new data is another thing that measurement devices don't do.

Let's do a little thought experiment. Do you contend that the ears+brain is "finer than any test equipment or computer ever made" *up to this moment*, leaving open that there may one day be a better setup, or the ears and brain better than any test equipment or computer than CAN EVER be built?

By the way, before we get done, you're going to have to define what exactly you mean by "finer", too.

[Chuck H]

Somebody thought of oil filled paper metal capacitors to "dampen" that vibration and isolate the component from being affected by vibrations. Or to soften the affect.

Well, back in "the day" they didn't have the same materials, machinery or precision that we enjoy today. I'm sure a comparably loose wrapped and entirely un-filled capacitor could surely be microphonic. But now they are very tightly wrapped and filled with space age goop. And I HAVE tried it. My limited personal experience on the matter has never revealed a microphonic film capacitor. To think such I would need to hear a louder noise tapping the capacitor than I do the resistor right next to it. That hasn't happened to me yet. The noise is always the same and loudest when I tap the first preamp tube. So I've concluded that it has always been vibration transfer to the tube itself. But this only reflects my personal experience. And I probably wouldn't be surprised to find a microphonic cap someday. As R.G. indicated, at some frequency all components will resonate and with enough energy will become microphonic.

Incidentally, When you go for the gasket goop don't get the black stuff. Get the blue stuff. IME some black automotive and plumbing products, like tubing and O-rings, have enough carbon in them to be conductive. I wouldn't take the chance with the black gasket material because of this experience.

[Enzo]

I have found disc ceramics sometimes microphonic, but not usually overly so. I have found more microphonic pieces of shielded cable than I have caps, frankly.

[R.G.]

Guruman is trying to confuse a philosophical point and a technological point. You ears are not measuring devices, they are transducers. ... To claim otherwise is to cling to some sort of romantic notion of human perfection.

There may be things we do not yet know how to properly measure, or we may not have a good idea how to put measurements into a meaningful context, but that is not at all the same thing as being not measurable.

Very well said, indeed Enzo.

Your post apparently went up while I was typing.

I have found disc ceramics sometimes microphonic, but not usually overly so. I have found more microphonic pieces of shielded cable than I have caps, frankly.

I've run into a very few *very* microphonic ceramic caps, but I'm nearly always amazed at the noise one gets from input cables as well.

The solution to many microphonics issues is damping. In lots of cases, the actual amount of microphonic sensitivity is not huge. But mechanical resonances have huge Q's, much larger than we can get in electronics without active amplification. So the actual vibration-to-electricity gets made larger because the amplitude of the mechanical vibrations is multiplied hundreds of times by the resonance. Even a little damping cuts that down a lot.