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In Reply to: RE: facing the loss posted by GSH on June 26, 2012 at 10:18:40
what you just discovered has been known for a long time, although not by everyone in the audio community! If you bypass a coupling cap, you will get a smeared result. If you don't hear it then your system has resolution problems. With coupling caps, you just have to give it your best shot.The problem has to do with the specs of the cap- series resistance and dissipation factor being two of the bigger players. Smaller caps tend to be better in these regards and can pass the signal in a 'faster' (that's how our ears hear it...) way. It is something that is measurable as well as audible- 'slow' caps will have less bandwidth although you might have to go quite high to see where the differences are.
Paper and oil caps are actually not bad in this regard and is why they are still around in audio. Teflon caps are good in this way too (but tend to be less prone to electrical leakage issues; they can be easily damaged with minor handling). The next best is polystyrene, which as some audio frequencies *can* be better than Teflon...
Edits: 06/26/12 06/26/12Follow Ups:
As stated, I only tried it on a PS cap, there is no "coupling" caps in a direct coupled SE amplifier, unless a cathode by-pass qualifies.
And yes, I see that caps have different speeds or bandwidth preferences, but this is NOT good! It means only very very high quality (if that exists) can "replace" the need to compensate with somehow "chosen" multiple small value paralleled caps. I hate it! But, I accept the challenge of at least trying to compensate for true losses. It is seemingly a necessary voodoo.
Can anyone recommend a cap that when paralleled with quality small caps,
doesn't sound ANY different? for example a 50uf/600VDC ? This to me would indicate that the speed/bandwidth performance of the main cap was "good enough" to not be enhanced by whatever "superior, less lossy" effects the additional caps could provide, along with whatever "smear" they are also adding?
Hi GSH,There is a difference between bypassing a power supply cap and a Rk cap.
Rk caps are somewhat more critical.
DynamiCaps allow for intelligent multiple film cap Rk bypassing, and according to Dennis Fraker, he finds they "add" very nicely.
A good solution / answer will be to use and trust your ears, to select bypass values and types. Use several differing values to get a linear music presentation.
There is no single Rk cap that will do all the frequencies at the speaker voice coil in a linear fashion. When you use a single cap on a Rk bypass, the music will unfortunately tune to the value of that one cap.
Cheers,
Jeff Medwin
Edits: 06/26/12
In your terms Drlowmu, what total Rk bypass value do you consider excessive?
It is excessive when the total value slows down the music's presentation.
Jeff Medwin
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