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Resistor noise notes 
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1N4001 - Signed up
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Joined: Tue Jun 10, 2008 5:17 pm
Posts: 1607
As found here. viewtopic.php?f=58&t=1218&start=146

The high lights, a 5% resistor can be obtained with specific technologies. 1% resistors costs about the same and use a different technology. The % spec isn't just the long term resistor ratting, but also the short term. Variations will happen as you pump in an AC signal, which will cause a wave of heat across the chip. This wave of heat will cause a wave of thermal expansion, which will cause the resistor to wonder in the 5% range. In an amplifier design(s), this can cause noticeable acoustic noise when driving a speaker. So might as well use the 1% resistors, as they cost nearly the same, and are better.

Here's a copy of Fred's post,
Vishay application note:

"Carbon composition resistors can exhibit a noise index of 0 dB while bulk metal foil resistors may have a noise index of -40 dB, usually making the excess noise of metal foil resistors insignificant." ... rmal_noise

Yes, I realise that it's not really applicable to engine management, but you may as well have the best where you can have them with no downsides including no excess cost :-)

Sun Jul 24, 2011 11:44 am
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Joined: Tue Jan 15, 2008 2:31 pm
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BTW, my old MS2/V3.0 was built entirely with 1/4W packaging, 1/2W dissipation, 1%, MF resistors, even in the locations intended for 1/8W packaging, though I know this is not ideal for vibration resistance. The MF stuff also tends to handle heat better. They're just generally superior, really. Good idea to stash it here. I really should rename this section.

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Sun Jul 24, 2011 4:38 pm
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