Re: Ignorance is Bliss
virtual.ray wrote: Hi Skippy, thanks for your interesting story. I'll freely admit I've never heard of some of the stuff you mentioned in it, and from the outcome of the tale, I'm glad that this is the case.
Oh, yes indeed. I wish that I'd never heard of some of it: it's like learning to see the cue dots while watching movies, or learning the sound of a tape splice made with a razor blade that wasn't properly demagnetized. That's the sort of knowledge that messes with your mind...
Background: in the late '70s and early '80s, one particular camp of activist audiophiles took it upon themselves to preach the gospel of "DC blocking caps are bad". These weren't the kind that write nasty equipment reviews: they had soldering irons, and they weren't afraid to use them.
Nerd talk follows. In circuit design, designers often build gain stages that have different DC operating points. To couple the output of one stage to the input of the next, you pass the signal through a capacitor: it passes the AC component that you care about, and blocks the DC component so that the two stages do not attempt to debias one another (which sometimes lets the Magic Smoke out). You size the cap so that the low frequency rolloff caused by the RC highpass filter you just built (cap value vs. driving point impedance) is below the frequency band of interest, yadda yadda. No big deal- it is (or used to be, anyway) first year EE stuff.
These days, most designers are more comfortable designing DC-coupled equipment (because of the ready availability of monolithic opamps that really make it pretty easy to do). This just ties gain stages together with a piece of wire, and eliminates those caps. It used to take a lot more circuitry to do direct-coupled, but since that's now all included inside those little multilegged platic things, it's no longer too expensive to consider... But that's fast-forwarding a couple of decades.
Now, as with all ideas run amok, there is more than a little truth to the "blocking caps are bad" idea. The temptation certainly exists to use an electrolytic capacitor for the DC blocking function: they tend to be very small for their values, relative to dry types. However, the ones you can afford to use in a commercial design are polar: they have a very definite + and - end, and biasing them up in reverse polarity leads to some problems. And they exhibit a hysteresis curve when you pass large signals: i.e., if you crank big voltage swings through them with no feedback, they actually can be shown to induce significant and measurable harmonic distortion.
There, I said it: if you're a freakin' screwup, you can design equipment with higher-than-necessary distortion numbers by using them. True fact, not in question. Now, you can also control this problem by decent circuit design practices. Many, if not most, of the most revered pieces of recording and reproduction equipment did and still do use good old gnarly nasty electros for this function. However, that was regarded as beside the point by the anointed. The bunch of crazies I let into my room decided that if any of them were bad, they must *all* be bad.
This was also the time in which wet-slug tantalum electrolytics were really beginning to come down in price, and be used a lot. This variation of the electrolytic capacitor is part of what has made miniaturization of modern gear possible: they pack an obscene amount of surface area into a teensy package, letting really big caps be put into really small places. The audiophile brigade immediately announced that they could be *heard* ("They induce a certain distinct graininess in the 11-11.25 kHz range, you putz!"), and away they went.
Of course, I shouldn't have been suprised. These guys would look through bins of components with a magnet, trying to find resistors and capacitors with pure copper leads (instead of copper-plated steel), since they could "hear the ringing cause by the inductance of the steel leads"). Good luck, dudes: essentially _all_ modern big ol' components have steel leads, so that they won't fall off the board if you shake it.
Sigh.
What followed was a two-year jihad against the electrolytic capacitor (and especially the never-to-be-sufficiently-damned tantalum!) carried out on the battlefield of my control room. I ended up with some equipment that was pretty ugly on the inside: replacing a little 1/4" teardrop tantalum with a fist-size polyester film cap in parallel with a little teeny mica cap (with copper leads, of course, for "transparency on the high end"). My compressors looked like they'd developed tumors, or something. I should have been a lot more bastardly in insisting on seeing the circuit design calculations. Hell, I shoulda had my _head examined_.
The speaker wire thing was much the same, but I've had enough sadistic necropheliac bestiality for one day: which is to say, enough beating the dead horse, already. Anyway, I'm quite convinced that these guys were hearing the voices of the angels, and their shared delusion was a sight to behold. It was also one of the major reasons that I sold the studio, stopped designing audio gear, stopped playing music at all, and went off to do other things with my life: I couldn't freakin' _stand_ it.
So now I'm getting back in after well over a decade on vacation from music. I'm glad to hear that those jihads have been abandoned. Presumably, the fashions have changed and the audiophiles have found something else to chase down: I can damned near smell the smoke, already. And you can bet your buns that whatever it is, I'll *ignore it*!
