Resistor Sound Quality?

[Christer]

Yes, I realize there is thermal inertia, so we wouldn't get any distorsion in the normal sense, like THD. However, what if there is a fortissimo passage so the resistor will dissipate a high power for a while. It will warm up slowly and if it is the feedback resistor, that means the gain of the amp will change slowly. Whether such an effect would be audible is another issue.

[Upupa Epops]

To Christer : Thermal inertia is faster, than you mean... By some papers caused rise of distortion on low frequency during only each periode ....

[Christer]

Originally posted by Upupa Epops
To Christer : Thermal inertia is faster, than you mean... By some papers caused rise of distortion on low frequency during only each periode ....

OK, well I had no idea how quick or slow it is, but since SY seemed to say it is very slow, I assumed it is.

Do you have any opinion on my suggestion that the feedback resistor would be the most sensitive to these effects in normal amps?

[Upupa Epops]

Yes, I agree...I'm using at this position in every time " overdimensioned " resistors...

[Christer]

Originally posted by Upupa Epops
Yes, I agree...I'm using at this position in every time " overdimensioned " resistors...

Interesting. That was what I had in mind, but so far it has only been a theoretical speculation from my side that it might be a good idea to overdimension it. Seems I wasn't too wrong there then.

[SY]

It is indeed slow- try measuring it.

In many uses (e.g., collector/drain/plate loads), the presence or absence of AC signal will not change the dissipation. Not true of feedback resistors, of course, where you want the lowest TCR and VCR attainable.

[jackinnj]

Carbon comps absorb humidity over time -- and the values change -- particularly true if you are using a carbon comp for the plate resistor in a preamp -- where it's going to get heated.

Carbon comps resistance becomes non-linear above a few hundred volts.

If you have a problem with the "drill-size" for the Allen Bradley cc resistors, just create a new component in your pcb software with the proper drill size.

The 1/4 and 0.4 w Yaego metal film resistors sold by Digikey use a 21 mil drill. A 1/2 W AB uses a 27 mil drill, 1 Watt AB use a 39 mil drill, for 2W use a 49 mil drill.

[sagarverma]

if what jack is sayin is right,then my component box is destined for a serious change

[StevenOH]

A lot of good info about different resistors can be found in Ben Duncan article "Piece de resistance" (recommended):
The Audio Amateur, 1994, 2-4, (revised and expanded).
Reprinted from: Hi-Fi News & Record Review, 1987, March.
Every good local library will have them.
You can find useful info about carbon composition resistors in "Art of Electronics" (Horowitz & Hill), p. 372, fig. 6.53.

[jcarr]

Dear Christer:

That was what I had in mind, but so far it has only been a theoretical speculation from my side that it might be a good idea to overdimension it. Seems I wasn't too wrong there then.

In the past, I have posted about nearly the same thing as you and Upupa Epops. Please see the following:

NFB resistor types vs. THD.

hth, jonathan carr