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Not trying to stir this up, but can anyone explain why a different type of cap., even in the signal path, can change 'tone', so long as the cap is of the specified value? My limited understanding of the physics involved, and having built a few amps and repaired many more, suggests that capacitance is capacitance.
There are cases - pickup magnets for example - where magnetism isn't just magnetism, and different grades do seem to affect tone, but in those cases the differences in flux density etc are measurable. A capacitor is a passive component and I find it very hard to understand how different types of caps of the same value can have different, or 'sweeter' frequency roll-offs, unless they are indeed of different values.
Happy to be educated..
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11-30-2015 07:10 AM
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There's just too much hype these days on the vintage gear market, specially on the US. The difference between real value and hype value completely distorts prices. Too many rich hobbyist I guess
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But if he said "Eureka! It has the original blumonium caps!", would you turn down his money?
Originally Posted by GNAPPI
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Of course not, I can readily separate a fool from his money. Originally Posted by Jim Soloway
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Mathematically speaking, capacitance is a complex function, it therefore has a real and imaginary part. The real part we usually just call "capacitance", whilst the imaginary part divided by the real part is known as the loss (or tan delta). Whilst the loss could possibly effect what you hear, for most modern capacitors the performance in circuit is more than 99% determined by the capacitance value alone. Both parts can vary as a function of temperature and as a function of the applied voltage amplitude and frequency. The "best" caps for audio use are therefore those which have the lowest loss and the least variation with temperature, applied voltage or frequency - my definition of "best" being those that have the least unintended impact on the signal. More often than not these will be polymer capacitors and, as you suspect, you should not be able to notice a difference between capacitors that have the same nominal spec. Hence, there is really no reason why one should pay more than a few cents or pennies for a "tone" capacitor. Originally Posted by Franz 1997
The worst type of capacitor I can imagine, from the point of view of predictability, repeatability and reliability, would be a paper & oil capacitor, which is why nobody except nutters make them these days.
Also, whilst we are on the subject, there is nothing special about Sprague Orange Drop capacitors, except that the quaint name appears to have given then an undeserved reputation in guitar circles. I should also say that there is nothing bad about them either !
Should you believe anything I've said ? Not really, but I'd like to think that 10 years working as a scientist in the capacitor industry and 15 years as a professor of electronic materials at a major UK university might lend my opinions some credibility.
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Thanks. Makes sense to me. Those impressive creds seem fair enough.. Originally Posted by newsense
Your comment about paper and oil caps are interesting; aren't these the most hyped variant?
All this seems to lead to the conclusion that psycho-acoustics is indeed a powerful force
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It's real good to see your comments. Originally Posted by newsense
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Interesting stuff Newsense, and I wouldn't argue with you. I agree with Franz too, psycho-acoustics is a powerful force!
On a side note, while I was trying out the various caps in a tele, when I put in the orange drop and re-mounted the control plate I found the cap worked sometimes and not others. After a lot of fiddling and trying alternative OD caps with the same results, I discovered that if the cap was very close to the (grounded) control plate, this caused the effect. moving it away by even 1/8" (2mm) stopped it cutting out. A sort of 'proximity effect' I guess. Any comments, Newsense?
I'm not the only one who finds a mica cap sweetens the bright cap in a Fender amp, its a common mod. In contrast, I think it was the late Ken Fischer, designer/builder of the highly desirable Trainwreck amps who advised used a ceramic cap in some guitar circuits to give a more gritty 'early Fender' sound.
Psycho-acoustics Rule!!!
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The only reason I use Sprague orange drop caps is because they are big and the values are easy to read with my failing eyesight.
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Oldane, I know it's a common mod, I just wish I could hear this 'sweetness' that some talk about. Anyway, assuming Newsense is right, the perceived 'sweetness' must be due to the cap not being within correct spec. ( presumably of a higher value, and therefore rolling off at lower freq.) rather than the materials the cap is made from, which has been ruled out as a factor by someone who knows what he is talking about. Originally Posted by bananafist
Interesting stuff Newsense, and I wouldn't argue with you. I agree with Franz too, psycho-acoustics is a powerful force!
I'm not the only one who finds a mica cap sweetens the bright cap in a Fender amp, its a common mod. In contrast, I think it was the late Ken Fischer, designer/builder of the highly desirable Trainwreck amps who advised used a ceramic cap in some guitar circuits to give a more gritty 'early Fender' sound.
Psycho-acoustics Rule!!!
Apart from a psycho-acoustic factor, of course.......we/ve all done the thing where, when installing a new pickup or whatever, we have convinced ourselves that there's a real improvement. Probably without psycho-acoustics, there would be no 'boutique' guitar parts industry, everyone would order spares from a commodity electronics warehouse somewhere.
Much less fun, much less to talk about, much less profit in it...
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There have been many so-called 'White Papers" written on why this cap sounds different than that cap, or why this one is superior to that one. I read ones with graphs from spectrum analyzers and impedance bridges and the data is used to 'prove' the original assertion. It can be very convincing but in the end I'm left with the impression that this could all be junk science and is really nothing more than marketing disguised as scientific proof, designed to justify the exorbitant pricing. I'm still in newsense's camp.
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Just to be clear - I think I said the nominal cap value accounts for 99% of the performance. Now, the other 1% is in the magnitude of dielectric loss and the frequency dependence of cap and loss, which can vary between capacitor types. Maybe that 1% difference between a mica and a ceramic cap, for example, is the sweetness people talk about. I guess they must have better ears than I have !
See, I'm a typical scientist - we give you all the science we know and then say "but maybe......", giving us an ideal opportunity to point out the last few details we're not sure about. We do this is in the hope that someone will pay us to answer these unanswered questions. Or to put it another way, I'm just looking for a legit opportunity to take some guitars into the lab and play with my impedance analyzers.
My other area of research is piezoelectric materials and someday I hope to answer the question why piezo pickups sound "scratchy".
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When I worked at IBM I worked in a component reliability (Mil-Hdbk 217-D analysis to be dating myself) and life testing lab for several years and I had lots of spare time and millions of dollars of lab equipment at my disposal. I was into synthesizers at the time and had built a rather elaborate PAIA synth and started diddling with the summing amplifiers to get 100% accurate octaves with patching panels. Then I thought about caps in guitars... why not? :-) Originally Posted by newsense
I had (or made) the opportunity to jury rig a guitar volume / tone circuit to a little amp and send known signals at the same amplitude thru the tone ckt with a function generator and change out cap types (same values) I had from home, power it up and record the waveshapes at various tone control levels on a TEK DSA-602 (with a FET probe) and later on recall the stored images.
No actual git was used because I figured I could never duplicate the ADSR 100% of the time by picking and fretting a string and no pups were installed, but the restored waveshapes overlaid each other favorably enough (and the waveform math calculator agreed) that over the years I just look (or hear) the other way when magic voodoo caps are mentioned.
From Seymour Duncan's site:
The capacitor only contributes to guitar’s tone when you lower the tone pot. If you always play with your tone pot wide open, none of this matters.
The value of the capacitor—denoted by a number—is what matters. However, the type of capacitor makes no audible difference whatsoever, though it can make a sizable difference on your wallet. (If that statement makes your hackles rise, read the postscript below.)Last edited by GNAPPI; 12-03-2015 at 01:28 AM.
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Multiple reasons from what I have read. Originally Posted by newsense
First, they send large voltage spikes to the preamp on the attack of the note and cause clipping for a fraction of a second. Using an 18v preamp reduces this by providing for more headroom. Notice that the piezo quack becomes more prominent when you pick or pluck harder because the attack transient is higher.
Second, the piezo is probably more accurately reproducing the sound of the string than does a magnetic pickup or a wooden guitar body. The piezo hears the note unmodified by the body at first with all the overtones being sent to the amp.
Third, it's a bridge pickup. Pick right by the bridge on any guitar and is sounds more like a piezo; pick by the 19th fret and you get a fat warm sound.
IME the best sounding under-saddle pickup is the D-TAR stuff from Seymour Duncan and Rick Turner. The piezo element hears in multiple directions and the 18v preamp provides a clearer signal to the amp. There are high and low pass filters to reduce "top thump" sensitivity and overtones, plus a regular tone and volume control. On my guitar with the tone at 50% the quack is gone but it still sounds acoustic (it's a Turner RN-6 and is actually a semi-hollow nylon string that sounds more acoustic amplified than any real acoustic-electric classical I've heard. The Godin is similar in construction and also sounds remarkably good).
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The genetic difference between humans and the chimpanzees is less than 2%. But the rest of the 98.x% is the same. I can't swing from branch to branch as fast as a chimp. And I don't have prehensile left and right feet. And chimps I meet at the zoo are miles cuter and more personable. Originally Posted by newsense
More's the pity.Last edited by Jabberwocky; 12-03-2015 at 04:14 AM.
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Well, IMHO, this comparison is a bit like comparing apples to oranges. Once I experimented with different caps, salvaged from different old radios and TV's. From what I remember, their type sort of mattered when they were in the signal path. When shunting the signal to ground, not that much, with the exception of ceramic capacitors, and especially those older ones, from the simple reason that they can be somewhat, or as I discovered during a gig once, a lot microphonic. Namely, during those experiments I found some caps that to my ears sounded almost like a wah back then, and that was long time ago. So, I say great, those are staying in there, and I went to a gig, which was a loud, rock gig. Every time I'd try to roll off the tone knob, to enjoy my invention, there was a nasty squeal - quite opposite of what happens when you have a microphonic pickup, right? Originally Posted by Jabberwocky
Some few years ago, after reading all the hype about PIO caps, and regretting of dumping my electronic junk stash, I found some cheap Russian PIO caps and put them in my LP type guitar. Well, I didn't hear much of a difference, that "woody tone" as they describe it, after replacing the regular film caps that were in there previously, except that, being large voltage caps, they are bulky and they take some more place in there.
So in my experience, it's all a snake oil, elixir of youth, or emperor's clothes, if you will. And the guy who decided to scan, and then to disassemble those Gibson "bumblebees" did the right thing. But funnier were the responses on the Gibson site, when those pics appeared for the first time. It was like, "oh, well, the magic and value is not only in the physics, but in a certain mojo, and we provide that mojo to our customers." And I bet those customers can hear the fake bumblebee mojo in a live band situation, with an overly processed signal.
I don't want to be rude, but, from where I come from there is a saying, roughly translated like this: "As long as there are sheep, there'll be wool".
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Where I come from there is also a saying that goes, Don't cast pearls before swine...or something to that effect...
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Well, in this context, I find that quote to be hilarious and arche-typical
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You guys with your "scientific tests." Of course you don't hear the difference between one capacitor and another. You're not using $200 cables to plug your guitar in, so how could you?
John
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I can't see air, but it's there, I can't see electricity but I believe in it, likewise I can't see a supreme being yet I believe. Originally Posted by John A.
Now what I "CAN" reveal with technology and actually see? I'll take as fact. Everything else is placebo.
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Holy epistemology Batman! We've created a monster (cable). Originally Posted by GNAPPI
John
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Vintage paper capacitors are notoriously unreliable. They are likely to change capacitance value or have insulators fail.
Cheap ceramic capacitors or modern capacitors are far superior to the old bumblebees. The bumblebee cosmetic reproductions are for the sole purpose of maintaining the cosmetic appearance of vintage instruments.
The only parameters that matter in tone caps are capacitance value and (if they are failing) insulation resistance. If two caps seem to have a different tone, either one of those parameters is different, there's a bad solder joint, or we're in the realm of psychoacoustics.
For those with a deep interest in vintage capacitors, here's the best info I've found.
http://antiqueradio.org/recap.htmLast edited by KirkP; 12-04-2015 at 12:43 PM.
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Sorry for reviving a month-old thread, but someone posted the following link on another thread and it seemed like excellent info to add to this one. Besides having audible examples of changing tone cap values, he makes a strong case that in an A-B test, any two capacitors with the same capacitance values will be indistinguishable in a tone control. Choose a reliable modern capacitor and don't worry about "mojo".
http://www.seymourduncan.com/tonefie...ize-your-caps/
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Everyone knows piezo pickups are made from ducks Originally Posted by newsense
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