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Input power vs Output power in pro amps

Discussion in 'Audio' started by morongo, Jun 6, 2019.

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  1. dave9


    Mar 5, 2017
    You could say they caved in to trying to combat the false nonsense specs others state, or you could say they are just another part of the problem.

    It's somewhat irrelevant. If you want to dive into audio, you're going to get your feet wet and have to hold your breath for a while because the rabbit hole goes much deeper.

    Let's get back to reality here. Class D? What wattage do you "really" need? I'd be far more comfortable with 30W class A. I like to be able to hear things.... no hearing damage.
  2. Audioguru


    Sep 24, 2016
    Since the very high power PRO amplifier is lightweight then its power supply also must use switching technology.
  3. BobK


    Jan 5, 2010
    You mean a combination amplifier & toaster oven?

  4. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Indeed. A few years ago (late in the previous century), we were using electron-beam furnaces to evaporate magnesium oxide and allow the vapor to sublimate on a hastalloy stainless steel tape, supplied from a reel-to-reel in-vacuum dispensing system. In addition to the electron-beam furnace at one end, there were three high-frequency, cylindrical, sputter deposition targets that the tape passed through to obtain additional thin-film coatings. If the process was successful, it was the first steps in obtaining a flexible "high temperature" superconducting ribbon that would operate at liquid nitrogen (77K) temperatures.

    We had been cruisin' along for years using a linear programmable DC power supply to power the furnace at a few thousand volts and a few dozen amperes of electron-beam current. This worked just fine IMHO, but along comes the manufacturer with their "new and improved" AC power supply using switched-mode Class D amplifiers. Ten kilowatts RMS in a box you could carry in one hand, power supply included. Plus all sorts of bells and whistles we didn't even know we wanted (or needed). And all this at a special price because we would be their first customer.

    So the program manager bought one. And it was dead on arrival. Opening it up we found a mish-mash of wires and tacked together components more appropriate to an R&D effort than a finished product. Took lots of pictures and sent it back. A few months later a replacement arrived. Looked inside and it appeared to be freshly assembled at a real factory. So, I connected it up, applied power, and awaited the results. Nada. This one was DOA too! Since no one was paying me to troubleshoot and "repair" an obviously deficient design, I told Accounting not to pay for it and went back to using our original analog power supply.

    Shortly afterward, the Air Force cancelled our R&D program, apparently because American Superconductor (AMSC) already had a product by then. As it turned out, American Superconductor did have a patented product, but the company was almost buried by China who paid an AMSC employee to steal the patented high-temperature superconductor technology. China then refused to pay for components already ordered, refused to accept delivery of components still in the delivery pipeline, and refused to honor the ASMC patents or offer to pay royalties, instead brazenly counterfeiting the components it formerly purchased from American Superconductor. The result was American Superconductor revenue dropped from one hundred million to ten million dollars per month, its stock price plummeted and just about everybody on Wall Street wrote it off for dead.

    Lesson to be learned from this: be damned careful how you do business with China!

    The Crown amplifier is probably a very good audio amplifier. The bugs associated with Class D modulation, mainly related to proper filtering to remove the ultrasonic carrier frequencies and associated harmonics and inter-modulation products, were solved decades ago for car audio systems. There is no reason to believe the technology has not migrated by now to home theater and public address systems. It certainly has proliferated in low-power personal-use electronics because of its simplicity and inexpensive implementation.

    As for the "power out versus power in" controversy, why not connect a recording power-line analyzer and make some measurements? However, as long as no fires are occurring in the mains wiring while blasting away with Freddy Mercury and Queen in a performance of "We Will Rock You!" before fifty thousand or so paid spectators, why bother and who cares? Enjoy the music.
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