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On Sat, 5 Mar 2011 08:33:54 -0800, Arny Krueger wrote
(in article ): A high gain stage might call for 33,000 Ohm resistor. OK, fine. I'll use a 33,000 Ohm resistor. But if I choose a carbon composition resistor instead of a metal film, that high gain stage will be noisy. You're joking, right? Nobody is using carbon composition resistors these days. No, I'm not joking. I was using an extreme case to make a point, and that SHOULD be obvious to even the most casual observer. Of course, nobody uses carbon comp resistors any more, but if one did use them throughout an amp design, that amp would sound different from one using metal film resistors. Same thing with capacitor selection. If my design called for a a series of coupling capacitors capacitor in the signal path and I used tantalum capacitors in those spots instead of a some kind of low DA film capacitor like a polypropylene or a mylar film capacitor, the amp circuit is going to sound different than it would had I used the low DA types of capacitors. Same story. I even had a well-known capacitor dielectric maven whose named rhymed with bung send me some good and bad capacitors to try in some projects. The so-called bad capacitors were simply not the part that long accepted wisdom said should be used in the application. The good capacitors were film capacitors but in actual use there was no measuable or audible benefit as compared again to what long accepted wisdom said should be used. IOW, Walt sent you some tantalums (or maybe some aluminum) electrolytics and some Polypropylenes? Tantalums shouldn't be used in audio circuits for a number of reasons, and you are right, the wisdom not use them is well known and long established, and I know that. But again, this is an extreme example to show that component type and quality can change the quality of an otherwise decent design. DA is important in sample-and-hold circuits and afew other applications. The fallacies associated with audio enthusiast misunderstandings of DA have been explained well by well-known and highly regarded experts such as Robert Pease of National Semiconductor. I know that he disagrees with Mr. Jung et al on this issue, but blind tests between two Hafler preamp kits, many years ago, one wired per the factory, and the other wired with "Wondercaps" in place of the factory supplied capacitors, showed conclusively that the "Wondercap" wired Hafler sounded much cleaner than the one wired with the factory caps. That and an experience where I replaced the Mylar film caps with "Wondercaps" in my Magnaplanar Tympani 3Cs (the ones with the eight panels) showed me conclusively (as far as I'm concerned) that Jung was correct about capacitor sound. |
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