audio2design
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I found this little ditty in one of his website,
Audio signals are AC. Cables cannot be directional any more than 2 + 2 can equal 5. Anyone prepared to believe this nonsense won't be capable of designing amplifiers, so there seems no point in further comment. (Doug Self)
Obviously in this post, Doug is saying the often repeated, but ridiculously incorrect statement that because audio signals are AC, that cables cannot be directional. Now for those with a half decent understanding of electronics and cables, you understand that a cable is essentially a network of resistors and inductors in series, with capacitors in parallel, with some parasitic additional inductance, resistance and capacitance. Since no cable is perfectly manufactured, those values will vary along the length of the cable, especially capacitance and inductance. Like any other two-port transfer function with capacitors and inductors, at AC frequencies, the input-output function is not the same as the output-input function, especially when source and load impedance is taken into account.
Simple fact, that excluding leakage current, the only time a cable is perfectly non directional is at DC. No this is not a statement of audibility. At audio frequencies, the two port function would be close enough to be the same in both direction, but, that is not what Doug's statement says. It says because the signals are AC, direction does not matter. That is wrong.
Now, I messaged Doug, expecting a "ya, that was not the most accurate statement". Nope, he doubled down on his statement claiming cables are symmetrical, which they absolutely are not as anyone who has done any good RF or even TDR work. I pointed this out, he just responded "you are wrong" and went off in a huff.
I have read much of his stuff, good, not exceptional, and remember thinking some conclusions / statements gave me pause. After this exchange, I have lost all respect for him, and fumbling such a simple concept, or at least being unable to admit a mistake, makes me question a lot more.
Audio signals are AC. Cables cannot be directional any more than 2 + 2 can equal 5. Anyone prepared to believe this nonsense won't be capable of designing amplifiers, so there seems no point in further comment. (Doug Self)
Obviously in this post, Doug is saying the often repeated, but ridiculously incorrect statement that because audio signals are AC, that cables cannot be directional. Now for those with a half decent understanding of electronics and cables, you understand that a cable is essentially a network of resistors and inductors in series, with capacitors in parallel, with some parasitic additional inductance, resistance and capacitance. Since no cable is perfectly manufactured, those values will vary along the length of the cable, especially capacitance and inductance. Like any other two-port transfer function with capacitors and inductors, at AC frequencies, the input-output function is not the same as the output-input function, especially when source and load impedance is taken into account.
Simple fact, that excluding leakage current, the only time a cable is perfectly non directional is at DC. No this is not a statement of audibility. At audio frequencies, the two port function would be close enough to be the same in both direction, but, that is not what Doug's statement says. It says because the signals are AC, direction does not matter. That is wrong.
Now, I messaged Doug, expecting a "ya, that was not the most accurate statement". Nope, he doubled down on his statement claiming cables are symmetrical, which they absolutely are not as anyone who has done any good RF or even TDR work. I pointed this out, he just responded "you are wrong" and went off in a huff.
I have read much of his stuff, good, not exceptional, and remember thinking some conclusions / statements gave me pause. After this exchange, I have lost all respect for him, and fumbling such a simple concept, or at least being unable to admit a mistake, makes me question a lot more.
