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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Thanks for a wonderful link! posted by Al Sekela on June 22, 2005 at 16:22:04:
>Some amps are sensitive to RF that gets in through the output terminals
Yes; that's true, and it's a pity. An admissible pity for PA sold $200, but a shame for those sold >$1000...
A well-designed equipment shall work as specified (and so, at the audiophile level for those PAs sold as audiophile) in any environment you can get in places where the equipment is intended to be used.
"any" environment includes standardized levels of RF pollution, radiated, inducted in coming out and coming in wires. Same with the AC power supply: common mode and differential RF current injection in wires, also variations in AC voltage (several limits depending of the duration of the perturbation), AC frequency, LF harmonics etc etc.
A necessary condition to say that an equipement is well-designed, again, is when it works as specifierd under those perturbation conditions, which means for an audiophile equipment you can't hear (and/or measure) any difference when perturbated or not.
Tha's the case of some equipement, happily.
For the others, you need external tweaks to get this result. In fact, you complete the weak design.
Is it so difficult to make by design equipments work in perturbated environment? Yes, it is often. And it cost about $10 for, say, a PA.
BTW, as audiophile equipment malfunctioning (or just working less-than-expected) is not life or property threatening, so risk of trials are null. So, emphasis is not put on these matters among manufacturers. Furthermore, since customers are happy to spend money for external tweaks and think it's normal, manufacturers have little encentive to make things better.
As for another area of consumer electronics, the automotive area , things are way different. During the first tests of ABS (anti-Blocking brake System), the equipement under test had the tendency to trigger at a tunnel entrance, from time to time. You bet the risks...However, the ABS passed the specified RF perturbation test.
It was shown that a military airbase radar was scanning some kilometers away, and when you get the beam just in the tunnel direction, constructive interference gave a RF level high enough to make the ABS computer to go havroc. Some time later, those higher than expected RF perturbation levels were included (with adequate margin) in the specification any critical automotive electronic equipment has to comply with in order to be certified and be put on the market.
If the car industry was like the audio, you would have to buy a separate shield for your ABS, to install by yourself. Some people would sell gold-plated shields (that work better, obviously) to set around the ABS box, some others would sell shields you put around the entire wheel, some would tell you you have to change the tires to their special rubber ones, cropped by wizards on leading moon nights on remote hevea trees in exotic countrie. Some would just sell nanostructure enabled Saint Christopher medals you pin on your dashboard.
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Follow Ups
- Re: Thanks for a wonderful link! - Jacques 00:58:02 06/23/05 (2)
- Thanks again for a thoroughly interesting discussion. - Al Sekela 13:44:54 06/23/05 (1)
- As with cars, except for those who buy Toyotas? Computers? Where not true? nt - Norm 14:00:02 06/23/05 (0)
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