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I hear people in the asylum advocating for mixing capacitor dielectrics thoughout an amplifier. Right now I'm listening to coupling capacitors in a breadboarded amp. I'm swapping film and foil, paper-in-oil, teflon, and waxed/oiled paper and foil.
My questions: I have a selection of caps in values of 0.1 muF, .047 muF, .068 muF, etc. I would like to try mixing dielectrics in a lower ratio than 10:1, which I understand to be a typical rule of thumb. For example, I'd like to parallel .068 and .047, 0.1 and 0.068, or even 0.047 and 0.047, each a different cap type within the paralleled set. What might be the upside and downside effects or risk in doing this? Would any characteristics of dielectrics be synergistic or would they tend toward neutralizing each other? Is the 10:1 ratio mostly a nod to keeping costs down, or are there other reasons for it?
My goal is three-fold: (1) transparency/accuracy, (2) full extension of bass and treble, and (3) still keeping some liveliness in the music. Perhaps unrealistic, but this is what I'm listening for. I like accurate sound without its becoming dull.
I am currently listening to and swapping FT-3, K40Y-9, K42Y-2, Panasonic film and foil ECQ-P(U), and vintage paper Good Alls (surprisingly extended and neutral!). The coupling cap value range I'm shooting for is 0.1 - 0.2 muF. I'm thinking about ordering some micas and kbgs to try as well.
Any thoughts on mixing dielectrics in the coupling capacitor location while also breaking the 10:1 ratio guideline?
Thanks,
Jeff
Follow Ups:
The russian ones, there is the SSG and one that has bigger vales, I think it's called KSG.
The SSG cap is the best sounding (like it's not there) cap I've heard.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Probably the best sounding .01 uF cap out there is the DynamiCap Hotrod version from Percy, but it costs real money sir.
Jeff Medwin
Years ago I came to the conclusion that bypassing a coupling cap ALWAYS introduced undesired side effects, so I never do it these days. If I had to use a very high value coupler, e.g., 1.0uF or above, I would consider touching it up with .01uF bypass using a cap of the same type. I would not ever recommend using a bypass cap that differs in construction from the main cap. This can give interesting and "technicolor" effects at times, but to me it usually does not sound like real music. This is really just my opinion based on my personal tastes or on my mental vision of what I am after in sonics. I don't think you can "fix" the sound of a coupler by adding another cap in parallel, without introducing unforeseen new issues.
I agree as well. I don't like bypassing either. If you are not happy with the sound of your circuit, cap rolling is unlikely to fix it. Try different circuit approaches.Best regards
Thomas
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http://vinylsavor.blogspot.com/
Edits: 03/12/11
Hi, Thomas,
I really like the sound of this amp. It's on the bench, so I'm cap rolling to see how things sound, not really trying to fix anything. Mostly personal curiosity to see what all the cap fuss is about. It's all good so far. In fact, the differences in the caps I mentioned in my original post are very subtle in this amp, and as they continue to take turns in the coupling spot, they are merging toward one another in detail and extension. It may come down to primarily size and space considerations.
Hi!
That's a good sign that the caps don't make big differences. This is an indication of a good design! Don't get fussed up about caps and enjoy your amp then!
Best regards
Thomas
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http://vinylsavor.blogspot.com/
A bypass cap always introduces problems for me. For example, adding a .01uf bypass across a coupling cap may impress initially with "speed" and "imaging focus" but, to my ears, these turn out to be colorations rather than improvements. It's like adding a super-tweeter to a speaker that is already well balanced. You notice the air and detail right away, but later conclude there is a discontinuity between the drivers. In my book, if you can hear the super-tweeter (or bypass cap), then it's a problem, not a solution.
I think it's far better to choose a better cap to begin with and then use it without a bypass. I like V-Caps for couplers.
I'm with Lew. Install a quality cap in the first place.
Thanks Lew and Neff,
I have good caps to select from; just checking to see what people think about this idea of mixed dielectrics in the coupling spot. I will be using a mix of capacitor types elsewhere around the amp, especially in the power supply, bypassing 'lytics with films or motor runs. I certainly don't want "technicolor" results for coupling; just the opposite, in fact.
--Jeff
Bypass there has solid reasoning behind it. Morgan Jones recommends the "1% Rule" (not 10%, but he's not dogmatic about it), and that's what I generally do.
... with the cathode bypass cap?I did this with an EL84 SET amp (made in Japan) and it did wonders for transparency - as though the caps cancelled themselves out of the signal chain.
Ymmv.
Edits: 03/11/11
Hi mpathus,
If you have one cathode bias cap, even a high quality cap - say a film cap, the music tends to tune to that one cap's value. It is better to plan to use a variety of Rk values, listening to the speaker's response (at the voice coil), so as to carefully determine your values, and cap types.
I have been told that the film caps that mix values best, and maintain relative coherency, are DynamiCaps, hence I use mostly them across my Rks, and in other places, in multiple values.
Be advised, there is NO one brand that makes great sounding caps in ALL values, certain values will sound better than others, and it differs with brand.
This is where some of the "art" in "audio-art" exists. No one I personally know of in audio comes close to my old friend Dennis Fraker in knowing all about this, for at least the last 20 years, and executing this to the Queen's taste. Cheers.
Jeff Medwin
Interesting idea! In this case, I'm using LEDs for bias with no bypass in the driver tube, but I will keep this in mind for another amp that uses cathode bypass, or perhaps for the output tube finals' bypass.
It's DIY so there are no guidelines :) Use whatever ratio/cap combination you find sounds best
Al
I like your perspective, Al!
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