Scott,
I think we both get annoyed by data used out of context.
I suspect that when the data shows that a resistor's distortion is -95 db at 1/4 power, when used as the feed back resistor in a power amplifier where it might actually briefly see full power, that may be bad enough to be heard directly.
It is interesting to me that when I ask some folks for their impressions as to which resistor sounds best as a phono termination resistor their impressions track what is measured as a difference in the some of the harmonic distortion at a higher level.
Is it coincidence? Is there some related mechanism? I don't know.
But when I find a $.016 resistor that measures as well as a $12.00 part I'll use the $.016 piece.
If I find two of the same price resistors have different distortion levels at 1/4 power I will use the one with the lower distortion. Does it make a difference, don't know, but it would be silly to knowingly use an inferior part.
But the biggest lesson learned is don't use resistors close to their power rating in sensitive applications. And that is practical information that can be used for more than audio.
I am perfectly happy showing my method for making measurements and some of my results. I want anyone to be able to repeat the tests. When others do and get the same results that is real engineering.
When someone offers an opinion, I will gladly try it out. If it works I may try more of their suggestions, if it doesn't less and less until "Please go annoy someone else" or the much less polite version of that.
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Hi Scott,
I have heard that resistors formed in an IC can be non-linear. I have no experience with this, and I have read that steps can be taken to reduce this. You would seem to be an excellent person to ask if there is much truth to this. Please pardon me if this is a stupid question.
-Chris
No, it's not that kind of thing. Some resistors do have a value dependence on applied voltage. Carbon composition types are an example of this, as if there weren't enough problems with them already. I have even found inductive metal film resistors, discovered with an HP 4263A, a cheap HP LCR meter. That both surprised me and explained some odd circuit performance. I was just happy to understand why the circuit was behaving as it was. (CD player RF amp).
I have heard that resistors formed in an IC can be non-linear. I have no experience with this, and I have read that steps can be taken to reduce this. You would seem to be an excellent person to ask if there is much truth to this. Please pardon me if this is a stupid question.
No one who has read any data sheets! Another very worthwhile exercise, reading data sheets and app notes. That's where I've learned far more than was taught in school.
-Chris
Hi Simon7000,
I have to agree with everything there. If a difference can be measured, then whatever the difference is warrants concern. Otherwise it doesn't seem to matter very much. I would include being able to hear a difference as a valid test if what is heard can be proved statistically.
A practical example for people to learn from. The original part was either 0.6 watt or 1 watt metal film, I can't remember which. The "fix" was to put two twice valued resistors in parallel to handle additional power. Still too close to the hairy edge, but at least they stopped putting holes in the PCB.
What the devil was the reviewer doing when this happened I wonder? Probably something well out of the norm.
-Chris
I have to agree with everything there. If a difference can be measured, then whatever the difference is warrants concern. Otherwise it doesn't seem to matter very much. I would include being able to hear a difference as a valid test if what is heard can be proved statistically.
There was a Carver amplifier that had an under-rated feedback resistor from the output back. It not only would overheat, it would burn a large oval hole in the PCB on it's way to Valhalla. This resulted in things like blown outputs and badly abused speakers. It was an amazing thing to see (and smell).
A practical example for people to learn from. The original part was either 0.6 watt or 1 watt metal film, I can't remember which. The "fix" was to put two twice valued resistors in parallel to handle additional power. Still too close to the hairy edge, but at least they stopped putting holes in the PCB.
What the devil was the reviewer doing when this happened I wonder? Probably something well out of the norm.
-Chris
I doubt that, I would need some fairly compelling evidence. Too bad we still can't get folks from each side together and do even a casual "there did you hear that?" We went through the numbers before these effects go as V squared so we're talking -200dB or more at phono levels.
An IMPORTANT problem that is being ignored here, is the presence of crossover distortion artifacts that occur at low levels. Not every junction is perfect and actual physical spaces can exist that cannot be 'jumped over' at low levels.
Now, I am not a real NUT about phono loading resistor quality. I use the best, because I use it everywhere else, AND the devices I chose have very low EXCESS NOISE above and beyond the nominal noise.
Now, I am not a real NUT about phono loading resistor quality. I use the best, because I use it everywhere else, AND the devices I chose have very low EXCESS NOISE above and beyond the nominal noise.
however "conventional" engineering in my reading, practice designing industrial/scientific instrumentation electronics says that "excess noise" is only present with current flow and thus would be expected to be immeasurable for mV AC signal conditions of phono cart loading R
authors of books, app notes such as Ott, Morrison, Brown, Pease, Williams are all wrong?
Certainly low excess noise is also a property of lower tempco, vcoeff resistor types as well – but I wouldn’t consider it a valid selection criteria in this app
How about “electronic cooling” – treated in Self’s Small Signal Audio Design book – good for a extra dB or so with mm cart?
authors of books, app notes such as Ott, Morrison, Brown, Pease, Williams are all wrong?
Certainly low excess noise is also a property of lower tempco, vcoeff resistor types as well – but I wouldn’t consider it a valid selection criteria in this app
How about “electronic cooling” – treated in Self’s Small Signal Audio Design book – good for a extra dB or so with mm cart?
Try a magnet on the section of lead that goes through the glass, chances are it is Kovar...
Seeing as how you dislike magnetic materials in the path.
Wrinkle, you are RIGHT, AND the leads are MAGNETIC! But 30 years ago, when I bought these beautiful resistors, I didn't care if the leads were magnetic or not! Why should I? It was when my preamp design FAILED to sound good, that I had a second look at the resistors. I have the preamp prototype in my closet. It has a dual Penny and Giles linear throw, audio taper, studio attenuater, etc. Maybe, now that we 'know' that I must have imagined any audio problems, someone would like to take it over. I have a dozen projects like that around here. Lots of pretty resistors for sale, maybe I should offer them here, online.
Weeeelllll, I think you should look at this patent...
US3054067
Electronic circuit comprising complementary symmetrical transistors - Patent 3927333 and open the pdf to see the original
Just look at the filing date!!!
Wrinkle
Very interesting.
James Bongiorno had same ideas around that time in his SAE MarkIIICM amplifier....and also his GAS preamps!
SAE is Scientific Audio Electronics history and models
James Bongiorno Designs
Attachments
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I am officially an idiot, I should have checked my own link, that is much too late to be interesting. The link I should have given is
us patent 3054067
Transistor signal amplifier circuit - Patent 3054067
again open the pdf for the text in your browser or downloaded.
Wrinkle
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