I did answer that already - Copper Oxide was the first form of a semiconductor. And any oxygen means there will, eventually, be oxydation of the crystal copper, yielding what should be conductor to become an unending series of diodes connected in random directions.
Nope. Sorry my friend but you don't know what you're talking about. Just more audiophile mythology based on ignorance.
First, Cu/CuO/Cu, which is the scenario you're describing here, does not make a diode. For that you need Cu/CuO and then something OTHER than Cu to make a diode. Look up the construction of a real copper oxide diode. I believe lead was pretty commonly used.
Second, you clearly don't even understand how a diode works. I'll spare you the solid state physics behind it and just leave it this.
Even if the scenario you give above did create a bunch of copper oxide diodes, what you have to understand about semiconductor diodes, even before they will begin to conduct current in the direction they're supposed to conduct current (in other words the opposite of the direction that it isn't supposed to conduct current and be "off"), the voltage across the diode must equal or exceed its forward conducting voltage. In the case of copper oxide, this is about 0.3 volts. In the case of silicon, about 0.7 volts.
In the microscopically small span of these diodes you're talking about, there would never be a voltage across that micro diode that equaled or exceeded 0.3 volts. So there would never be any current flowing through them in either direction, let alone current flowing in one direction and being blocked in the other, which is what happens when a real diode is functioning.
Third, ETP copper, while an "oxygenated" copper, only uses very small (on the order of 0.04%), very precisely controlled amounts of oxygen. ETP starts out with pretty pure copper to begin with. At least 99.95%. The purpose of the oxygen is to scavenge the remaining impurities and remove them from solution. The result is a copper with a higher conductivity. In other words, a copper with the same percentage of impurities, has a lower conductivity than the same copper employing oxygen scavenging. And with the oxygen bound to the impurities, it can't react with the copper to form the copper oxide you're so deathly afraid of.
To test this theory, Japanese went to the most extreme possible of extremes - mercury cables. ZERO crystals (as mercury is liquid - except at terminations ), sealed from the atmosphere, whatever oxygen still entering the equation, would not be enough to "rot" anything but the surface of the mercury. These cables allegedly sounded superb - out of this world superb.
That's the problem when people are ignorant of the facts, fantasize about "problems" that don't exist, and then come up with a "cure" for those non-existent problems. But because they're convinced that the "cure" must result in a cable that's "better," then those subjective biases will tend to "confirm" that it sounds better.
To "test this theory" would have required nothing more than a simple distortion test. Diodes are nonlinear. So any diodic action going on in the cable will produce harmonic and intermodulation distortion.
Several years ago I provided a number of cables to Bruno Putzeys, currently with Hypex but at the time was with Philips.
He found no distortion down to about -145 dB, which was the noise limit of the measurements. And one of the cables I sent him was a cheap cable I'd bought at Radio Shack that was about 10 years old. And I'd bet if I pulled out some of the 60+ year old AC wiring from my walls, cleaned off the ends and soldered some connectors to it, you would get the same result. The "theory" is based on a complete lack of understanding.
Practical realization was oxygen free copper with as long crystals as possible (on the order of half a metre or so...) - all intended to approximate the performance of the impractical (not to mention poisenous...) holy grail of cables - the mercury cable.
Pure nonsense.
The only "problem" with ETP copper is when you heat it in a reducing atmosphere, such as hydrogen as you might find in a hydrogen annealing furnace, like my transformer guy uses to anneal his transformer laminations. The hydrogen can penetrate the copper and react with the oxygen which can embrittle the copper and cause it to fail.
That's what oxygen free copper is for. But it was latched onto by a bunch of audiophiles many years ago as a "superior" copper and has been a meaningless buzzword ever since. At least until they latched onto OCC.
If you want to learn about materials properties, the absolute LAST place you should go to get it is a bunch of neurotic audiophiles and "high end" audio manufacturers. Get a REAL materials properties text. I recommend Hummel's
Electronic Properties of Materials as a good place to start. Otherwise, all you're doing is embarrassing yourself by perpetuating all this mythological nonsense.
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