24.13.232.33
In Reply to: RE: Measuring properties or changing operation? posted by bjh on June 24, 2009 at 11:40:54
"things like power line conditioning and power cords *do* often still make a difference. "
Yes, it's true perhaps but when it's true then also it is evidence that the power supply design is incomplete.
Noise "can" be a problem if your design doesn't deal with it, then an external bandaid can help beyond decoration.
Since it is possible to make power supplies which are extremly immune to huge line noise, possible to make radio transmitters with sensitive audio circuitry, even possible to make sensitive electronics operate in close proximity to an xenon arc lamp, what would be the reason (other than cost or knowledge) not to design for noise immunity like that in modern hifi gear?
This problem is not new either, one couldn't design a tube amplifier in the old days without addressing RF and noise.
Most output tubes and all small signal tubes would work perfectly happily up to Citizen's band (27 MHz) if allowed to, not like transistors which have vastly lower open bandwidth.
In the old days there were mare severe sources of noise too, in the last 20 years these sources were replaced to permit the cell phone and wireless era high up in frequency.
My point is as a designer, one is left thinking the job is not done if an external shield / AC cord etc actually changes the operation.
Think about it this way, It is "foolish engineering" to leave the proper operation of a circuit or system to depend on having "the right" kind of AC, especially since one can remove that issue at least over some range with proper design.
Testing the actual operating voltage range and tolerance / immunity to input distortion / noise is normal stuff, at least when making test equipment.
Possible reasons for the way it is;
Audio design, especially power analogue circuitry, is a much much smaller business than "test equipment", fewer Ham's and DIY'rs now in the field, who are good self taught designers and perhaps the very presence of the "mystery of the magic cord" and such enhances part of the industry's image and romance among the buyers
Just a wild guess.
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