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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old Today, 03:01 PM   #25521
scott wurcer is online now scott wurcer  United States
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Join Date: Jan 2004
Location: Belmont MA
Quote:
Originally Posted by Joe Rasmussen View Post
or maybe you are not a fan of Faraday?
I'm pretty sure Faraday understood complex algebra he certainly knew the current and voltage in an inductor were not in phase. Adding the modulus of the impedance of the resistor to that of the inductor is the wrong answer.
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Last edited by scott wurcer; Today at 03:07 PM.
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Old Today, 03:02 PM   #25522
AllenB is online now AllenB  Australia
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Quote:
Originally Posted by Joe Rasmussen View Post
And somebody (me) should tell "DF" that complex numbers are not needed to explain something that can already be explained by Ohm's Law.
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Old Today, 03:07 PM   #25523
simon7000 is offline simon7000  United States
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The issue started with Scott Wurcer denying that there were problems with dirty contacts not passing signal until a voltage threshold was reached and then they would work.

He then raised the issue of gas dielectric break over which really had nothing to do with the normal connector contact issue of air carried contamination.

After having a few folks confirm that audio contacts do get dirty and cleaning them helps he has gone back to his bit as how do relays work reliably.

That answer of course is use the right relay and for his particular case those would be sealed relays that for some strange reason don't suffer from air exposure.

Then reasonable folks asked why reed relays aren't used more for audio and the answer is simple, the reed needs to be magnetic and that introduces hysteresis in the signal based magnetic field. Yes that is at an extremely low level but since it is easily avoided by other types of relays reed relays are rarely used.

Western Electric developed the most reliable relays for use in the telephone system. These use bifurcated crossbar contacts so that there are four points of high pressure contact for each switch. They then made their own alloy to withstand the enormous number of closures they expected the relays to withstand. The modern version is of course much smaller and often uses gold over a silver base contacts. At the lowest levels the gold, which does not fail due to atmospheric junk, provides the contact surfaces. When the relay is used at higher voltage and current the gold burns off and you have the more rugged silver contacts. They would be effected by air carried junk except that the relay is handling enough voltage to clear such stuff in normal use. The problem is that once the relay has switched a high enough level to burn off the gold it should not be reused to carry the lower level signals.

Last edited by simon7000; Today at 03:09 PM.
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Old Today, 03:07 PM   #25524
Markw4 is online now Markw4  United States
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Joe,

Tutorial on Ohm's Law for AC circuits using complex algebra:
https://www.usna.edu/ECE/ee301/Lectu...0Impedance.pdf
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