[sdiy] Carbon composition... vs carbon film resistors.. original question..

[Jean-Pierre Desrochers]

Thanks Tom for the very detailed info about the specific differences !

JP

----- Original Message ----- 
From: "Tom Farrand" <mbedtom at gmail.com>
To: "Jean-Pierre Desrochers" <jpdesroc at oricom.ca>
Cc: <Synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, February 13, 2013 1:14 AM
Subject: Re: [sdiy] Carbon composition... vs carbon film resistors.. 
original question..


Jean-Pierre,

Carbon composition resistors have a larger voltage coefficient than
carbon film types.  That means the resistors themselves will introduce
more distortion in audio circuits than carbon film.  (Carbon Comp ~
350PPM, Carbon Film ~ 100 PPM voltage coefficient.)  Carbon film has a
better resistance versus operating temperature coefficient, than
carbon composition.  (Less resistance variation over temperature.)
Metal film is about the best, by the way.

In practical terms the behavior will be "similar" but not identical.
The outcomes you will get depend on the specific application.  For low
level signal amplification and processing, metal film is preferred by
a significant margin.  Carbon composition would probably be dead last
in preference and carbon film, slightly better than carbon
composition.  If the load is pulsed, as is common in "snubber"
circuits for TRIACs and motor control, carbon composition is king.

Carbon composition resistors cost more.  I just checked Digi-Key as an
example, for a 10K 1/4W resistor.  A 10K 1/4W carbon composition
resistor costs $19.31 per 100 units ($0.19 each).  A 10K 1/4W carbon
film resistor costs $2.20 per 100 units ($0.022 each).  The carbon
composition has a -700 to +400PPM temperature tolerance.  The carbon
film resistor has +/- 350 PPM temperature tolerance.  For price and
performance, the carbon film resistor is qualitatively "better".  But
at about $4.00 per 100 units, a metal film resistor has +/- 100 PPM
temperature tolerance and essentially a zero voltage coefficient ...
much better!

Unless the application requires a pulse withstand capability, I would
not use a carbon composition resistor for anything.  If you are
willing to pay for carbon composition resistors, buy metal film units
instead!

Specific enough?

Tom Farrand


On Tue, Feb 12, 2013 at 12:40 PM, Jean-Pierre Desrochers
<jpdesroc at oricom.ca> wrote:
>
> The actual going on this post is going very far from
> where the original question was...
> Here again my original post question:
>
> Reading the following info about resistor types :
> http://www.electronics-tutorials.ws/resistor/res_1.html
>
> Can I conclude that 5% -> carbon film <- type resistors like these :
> http://www.yageo.com/documents/recent/Leaded-R_CFR_2011.pdf
>
> will show the same audio circuit behaviours as the following 5% -> carbon 
> composition <- type :
> http://www.seielect.com/catalog/SEI-RC.pdf
>
> I already used the Yageo 5% resistors with Ok results
> where noise was not a big issue.. but I like very much the look of the
> Stackpole's
>
> Any differences between both types or they are the same overall..??
>
> JP
>
> -----------------------------------------------------------------------------------
>
> Le 2013-02-12 13:04, Barry Klein a écrit :
>>
>> Check this thread:
>>
>> http://www.geotech1.com/forums/showthread.php?20169-Need-advice-on-Minelab-11-quot-coil-repair-and-design
>> The resistor I am talking about is shown in comparison to the
>> original in-circuit one.
>> I suspect metal film.  No capacitance involved unless it's in the meter 
>> :-)
>> It is interesting to learn as - in the first place I did not expect
>> to see a damping resistor on an RX coil - then it skews the inductance
>> measurement of the coil and thus if you try and copy an existing
>> design you need to know whether there is a resistor there or not.
>> Too many hobbies already BTW.  I need to remain clueless with the ones I 
>> have.
>>
>> Barry
>>
>>
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Paul
>> Schreiber
>> Sent: Monday, February 11, 2013 10:37 PM
>> To: 'synth-diy'
>> Subject: Re: [sdiy] Carbon composition... vs carbon film resistors..
>>
>>> LC102 for inductance and got 233uH
>>
>>
>> According to the "math", that inductance would have to be in series
>> or parallel with *at least* 0.28uf just to have an effect at 20KHz.
>>
>> If your pc boards have 0.28uf of stay capacitance, get another hobby :)
>>
>> Paul S.
>>
>>
>>
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>
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