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Post by jkemmery on Aug 3, 2007 11:00:24 GMT -5
This is directed at those of us who actually believe that ceramic tone caps sound significantly different from other types of caps, specifically poly-film caps.
My question is what are the general thoughts on caps for trebel retainer circuits. Are ceramics acceptable for this application, or not? Since the value is so low and the effect somewhat minimal (compared to a tone cap) does it make a difference if it's an Orange Drop or a Mallory or a plain old ceramic. The adjuct to the question is, if all you have is a ceramic, is it better or worse than no trebel retainer cap at all?
Just some thoughts. Since I'm working on a rear-route guitar, I may take some time to do an A/B comparison ...
For what it's worth, I'll probably stick to polys unless the ceramic surprises me, since as has been pointed out before, the cost difference while as a percentage is great, a couple of bucks, at the most, for the cap does not significantly add to the cost of a build or upgrade. I was just curious about the thoughts of others on the board.
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Post by JohnH on Aug 3, 2007 15:08:24 GMT -5
This is directed at those of us who actually believe that ceramic tone caps sound significantly different from other types of caps, specifically poly-film caps. I'm disqualified straight away, since I don't believe that. However Ive heard it said quite a few times. My LP came with ceramic discs, and they sound like, well, tone caps. But I haven't done an A/B. I would think that if there is a benefit in a treble bleed cap, then its worth having it even with just a ceramic type. BTW, I use 1nF in parallel with a 220k resistor. cheers John |
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Apprentice Shielder
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Post by blank on Aug 3, 2007 15:10:51 GMT -5
damn, I never really gave it that much thought ya know? I feel like no matter what it's made of it's better to have it because turning the volume down without one is just useless to my ears. Just too MUDDY. If I didn't have a treble bleed cap on the volume I'd rather just have an on/off switch.
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Post by sumgai on Aug 4, 2007 13:47:57 GMT -5
John and/or Chris, Do your Spice proggies make any distinctions at all about what type of cap is being modeled? I should think that if there truly were major (audible) differences between cap types, then any decent Spice software would ask the designer for that info. Chris, you've noted that there are differences in quality that affect a capacitor's performance, but everything you mentioned is quantifiable, and therefore it's data that can be stored and manipulated just as any other parameter in the Spice engine.  Which prompts the question, are the engines "sparse" or are they that detailed? sumgai |
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Post by JohnH on Aug 4, 2007 15:37:24 GMT -5
Chris will know more certainly, but my understanding is that the simple components such as caps and resistors in Spice models are just perfect theoretical ones. eg, a cap has no leakage or inductance. If these secondary parameters for real-world components area measurable however, then they could be added. One might add a resistor across a cap to model leakage for example.
John
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Post by UnklMickey on Aug 4, 2007 18:14:29 GMT -5
Chris will know more certainly, but my understanding is that the simple components such as caps and resistors in Spice models are just perfect theoretical ones. eg, a cap has no leakage or inductance. If these secondary parameters for real-world components area measurable however, then they could be added. One might add a resistor across a cap to model leakage for example.
John John, back-in-the-day I was skeptical about what the "hi-fi" guys had to say about ceramics, but eventually accepted it, and took it on faith. Steve Bench did a bit of testing and his result seem to support the premise that ceramics are non-linear. It doesn't look like using a resistor in series will be enough to model this behaviour. members.aol.com/sbench102/caps.htmlOne facet to this discussion I find interesting is when we are talking about a guitar, we are often talking about desirable tone that is derived from artifacts that would be considered very undesirable in the hifi world. All the harmonic distortion that we revel in is considered pure evil for them. Leo has used ceramic caps in guitars for decades. If one is truly in search of the elusive "vintage tone", it would seem the "dirt" caused by ceramic tone caps might be a necessary part of the equation. Back to reality:I personally would avoid the ceramics, but I doubt it makes all that much difference. It will still have an effect with treble-bleed even though the values are small. If you are avoiding them, avoid them here as well. And if the loss of highs when rolling down the volume is an issue that is important for you to mitigate, using a ceramic cap would certainly be better than no cap. IMHO the resistor in the treble-bleed network is very important to keep any cap there from being too effective, and over-compensating. |
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Post by JohnH on Aug 4, 2007 20:16:21 GMT -5
Those Steve Bench 'Bench' tests do indeed show something non-linear with the ceramics. But he notes that the signal level is based on 70V. I think if I had a 70V signal in my guitar, it would be very non-linear, for all sorts of other reasons!
John
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Post by ChrisK on Aug 4, 2007 20:18:14 GMT -5
Ceramic caps have the potential to be lousy for audio work. They can have significant internal leakage (certainly bad for audio and high-impedance work) and piezo electric effects.
The internal leakage causes apparent/effective parallel resistance which changes the loading from ideal to unfortunately real. Film caps generally do not have this effect, but they can absorb moisture as well if not well sealed.
The piezo-electric effect is similar to dielectric absorption (if I have to explain it you likely won't understand it anyway) in its distortion added to the signal.
Heck, even carbon composition resistors (uh, like pot elements) generate noise IN AND OF THEMSELVES! (And I don't mean when their shafts are turned!)
I know of the leakage effect first-hand in having shipped automation products with high resolution analog sensor inputs in the 100,000's. If I could save a penny, I would, but knew when to spend when it was important. I used gazillions of ceramic caps, but only the right cap for each application. Z5U's for supply bypass (the cheap ceramic), X7R's for higher impedances (the better ceramic), NPO/COG for the important HF/RF stuff (the best ceramics), and film caps in polycarbonate when applicable and polypropylene when necessary.
These ranged from $0.02 to $2.00 in volume.
The problem is that the caps sold in the guitar parts industry are completely stripped of all specificity by the time they reach the vendors (and virtually all consumers thereof know nothing of specificity anyway).
It boils down to generalizations: film caps are generally better for tone (preservation) than ceramics.
pSpice can have resistance and inductance added to cap models (and resistance and capacitance to inductor models).
It's like the hunter that spends $1,000 for a new rifle, $1,000 for a new scope (what, you put cheap scopes on expensive rifles too?), $3,000 for the trip of a lifetime, and buys the cheapest ammo that he can find.
If you're going to take the time to invest in modding your guitar, use the best stuff, Sparky.
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Which prompts the question, are the engines "sparse" or are they that detailed?
