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Old 1st June 2003, 03:31 AM   #1
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Default does the resistor's ppm affect the sound?

newb question

low ppm resistors are more expensive (i am looking at dale rn60e/d family at mouser)...i was wondering if someone could educate me a little bit about the subjet and also if low ppm = better sound


thank you all
m.
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Old 1st June 2003, 04:13 AM   #2
haldor is offline haldor  United States
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Low ppm means that the resistors value doesn't change much as the temperature of the part changes.

This characteristic can have a huge impact on sound quality or it can be totally irrelevant. What the resistor is being used in the circuit determines if this is so.

For example I use 5 ppm resistors in a custom resistor array to set the gain of signal conditioning front end instrument amps (measuring a 10 mV differential signal to 20 bit precision). For emitter resistors on parallel output devices in a power amp I could care less about ppm.

Phil
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Old 1st June 2003, 04:22 AM   #3
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This is totally anecdotal, but I have rebuilt a lot of vintage tube amps, and I frequently listen to them for a while before rebuilding them (when possible). The originals almost always have carbon comp resistors, which are more temperature sensors than resistors. And the amps typically change their character audibly as they warm up. After a rebuild (almost invariably the same topology with modern high quality parts) they don't change their character with warm-up like they used to. The warm-up changes are very subtle if present at all.


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Old 1st June 2003, 06:22 AM   #4
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Question Sound of resistors

Quote:
Originally posted by stokessd
This is totally anecdotal, but I have rebuilt a lot of vintage tube amps, and I frequently listen to them for a while before rebuilding them (when possible). The originals almost always have carbon comp resistors, which are more temperature sensors than resistors. And the amps typically change their character audibly as they warm up. After a rebuild (almost invariably the same topology with modern high quality parts) they don't change their character with warm-up like they used to. The warm-up changes are very subtle if present at all.


Sheldon

Hi Sheldon,
And how does the sound of the rebuilt unit compare to the original with the carbon comp resistors?
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Old 1st June 2003, 10:23 AM   #5
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Metal film resistors definitely don't make as much "hiss" in low level stages as carbon resistors. ALL resistors make some noise though, the higher the R the greater the noise. Part of "the cussedness of Nature".
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Old 1st June 2003, 10:41 AM   #6
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Default White Noise Is A Mathmatical Construct...

Quote:
Originally posted by Circlotron
Metal film resistors definitely don't make as much "hiss" in low level stages as carbon resistors. ALL resistors make some noise though, the higher the R the greater the noise. Part of "the cussedness of Nature".
Yes the noise levels are different according to Carbon/Mf, and the spectrums are different too.

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Old 2nd June 2003, 01:40 AM   #7
Arzela is offline Arzela  United States
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What is "ppm" excatly? I
assume there is a linear relationship between
resistance and temperature throghout
a normal temperature range. Is ppm the
slope of the corresponding line? If
so, what are the standard units?

Sorry for the ignorant question...
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Old 2nd June 2003, 06:23 AM   #8
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hi Arzela

check this page....
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Old 4th June 2003, 04:19 AM   #9
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Default Re: Sound of resistors

Quote:
Originally posted by Elso Kwak
And how does the sound of the rebuilt unit compare to the original with the carbon comp resistors?
Different for sure. Typically the Carbon Comp resistors I pull out are drfted from their nominal values by a bit. So with the correct value resistors replacing them, I am now listening to an amp at different operating points.

Typically the sound of the carbon comp resistors and paper caps is a bit wooly, and recessed, but not really in a polite way.

A rebuilt amp sounds much more accurate and truthful to the signals I'm putting through it (I've recorded some of the material myself and I'm very familiar with it).

Sheldon
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Old 4th June 2003, 04:21 AM   #10
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Quote:
Originally posted by Arzela
What is "ppm" excatly? I
assume there is a linear relationship between
resistance and temperature throghout
a normal temperature range. Is ppm the
slope of the corresponding line? If
so, what are the standard units?

Sorry for the ignorant question...
It's parts per million, as in particulate counts etc. Think of it as a way to represent really small percentages. 1 PPM is really 0.0001% It's easier to write 33 PPM than 0.0033%

For resistors it's typically something like 50 ppm/deg c Or 0.005%/deg c.



Sheldon
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