Scott,
Did you read the thread?
We are not discussing Vishay bulk film resistors!!!
The issue was is there a Vishay resistor that in a feedback loop by itself will cause enough distortion to be noticed. I showed measurements on a not as good as the rest Vishay resistor model.
I also discussed how unweighted THD numbers can be misleading.
To produce an amplifier that has .01% THD at full power is by today's standards not very hard.
However such an amplifier can still not sound "State of the art" if the distortion rises as the level drops. There is nothing new or out of the mainstream about those issues.
If it weren't such a silly issue I would breadboard a circuit for you and show the results that can differ from just different types of feedback resistors. Op-amps today are being made with such small distortion that it is making the quality of other components more important. Or are you going to argue that opamps are inherently evil!
ES
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Ok drop it, no more comments without a full example to talk around. The distortion rising with drop in level is exactly the opposite of all these voltage coefficient issues. This is just a waste of time, post complete circuits so I know what you are talking about or just let it be.
Scott,
That would violate the unmentioned requirement to always be rude here.
However since things are really cooking here you will have to forgive me for violating that rule.
ES
It is known that SOME resistors can cause a significant amount of distortion. Richard Heyser described this to me, back in 1968. Back in those days, Allen Bradley was good enough for me. Six years later, in 1974, I ordered thousands of dollars of lab stock, including Allen Bradley potentiometers, that were sent from the USA to Switzerland. After all, Ampex used them, how could they be 'flawed'?
However, during a listening test John Meyer, and another associate noticed that my JC-2 was the apparent culprit, which at first, I could not believe. But finally, I said: 'Don't touch the volume control, etc, and I moved the JC-2 to my test bench with a Crown IMA distortion analyzer, that could measure to .001% reliably.
And there it was! Distortion, and some higher order distortion too! Move the pot and the distortion went away. Put the pot back in the same place and the distortion jumped up.
Then, I tried the Allen Bradley pots. They ALL distorted, usually lower order, but over a larger range of operation. It was there, but nobody ever looked. If I had not listened and believed Richard Heyser, perhaps 6 years earlier, I would probably not have been so open to the fact that a 'Waters' $20 dual pot (perhaps $100 today) could possibly have a significant amount of distortion with a nominal voltage through it. Expensive German pots were not free of distortion, either.
However, during a listening test John Meyer, and another associate noticed that my JC-2 was the apparent culprit, which at first, I could not believe. But finally, I said: 'Don't touch the volume control, etc, and I moved the JC-2 to my test bench with a Crown IMA distortion analyzer, that could measure to .001% reliably.
And there it was! Distortion, and some higher order distortion too! Move the pot and the distortion went away. Put the pot back in the same place and the distortion jumped up.
Then, I tried the Allen Bradley pots. They ALL distorted, usually lower order, but over a larger range of operation. It was there, but nobody ever looked. If I had not listened and believed Richard Heyser, perhaps 6 years earlier, I would probably not have been so open to the fact that a 'Waters' $20 dual pot (perhaps $100 today) could possibly have a significant amount of distortion with a nominal voltage through it. Expensive German pots were not free of distortion, either.
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Granted that some resistors (and potentiometer elements) have substantial voltage coefficients, to the extent that they are consistent among samples of the same value, one should be able to make voltage dividers using multiple parts in series and to a first approximation eliminate the voltage coefficient distortion --- and as well any thermal distortions. Of course for large division ratios this means a lot of resistors.
As far as excess noise (so-called "current" noise, not to be confused with normal thermal noise), I learned the hard way how terrible thick film SM parts can be (ghastly!). Some will say Well don't run d.c. through them. But the noise will then appear with signal swing, so although the system may have a reasonable noise floor at zero signal, there will be noise that is modulated by signal level.
As far as excess noise (so-called "current" noise, not to be confused with normal thermal noise), I learned the hard way how terrible thick film SM parts can be (ghastly!). Some will say Well don't run d.c. through them. But the noise will then appear with signal swing, so although the system may have a reasonable noise floor at zero signal, there will be noise that is modulated by signal level.
So what? Have you ever bothered to measure a pot? If not, why not? Are you careful how you use it in audio applications? Why would a first class company, like Allen Bradley, make a 2'd class professional pot? Why was there no warning on the spec sheet?
Waters was an extremely expensive precision pot. Yet we had to discontinue it, because of the distortion generating bad spots on the rotation.
Interestingly enough, neither Bourns, Clarostat, or P&G have the same problem, so far as we could measure, even though some pots looked almost exactly like the AB Mod. pot, go figure!
Waters was an extremely expensive precision pot. Yet we had to discontinue it, because of the distortion generating bad spots on the rotation.
Interestingly enough, neither Bourns, Clarostat, or P&G have the same problem, so far as we could measure, even though some pots looked almost exactly like the AB Mod. pot, go figure!
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Hi,
Well, as far as the "magic" part AMR uses, I am not allowed to say. But i have no problem if you mention which ones you found to be good.
What I can say is without reservation, that in my experience the best resistor for Audio are the Rohpoint precision Non-Inductive Wirewound resistors. I have been using them (and some other wirewounds) nearly exclusively for all my best personal stuff. They are a trifle expensive, but not forbiddingly so. You should test them.
I must admit also to using 10 Turn precision wirewound potentiomers as Volume control in the 80's (I even integrated them with a string based mechanism into professional mixer cassette faders). But the dual mono thing drove me nuts and the physiological EQ curve I could realise with these was suboptimal.
I was very much German Studio Gear influenced at the time, so I changed to a 30 position switched resistor attenuator with very complex RC networks for the loudness compensation EQ derived from the original Eckmiller faders...
Ciao T
Well, as far as the "magic" part AMR uses, I am not allowed to say. But i have no problem if you mention which ones you found to be good.
What I can say is without reservation, that in my experience the best resistor for Audio are the Rohpoint precision Non-Inductive Wirewound resistors. I have been using them (and some other wirewounds) nearly exclusively for all my best personal stuff. They are a trifle expensive, but not forbiddingly so. You should test them.
I must admit also to using 10 Turn precision wirewound potentiomers as Volume control in the 80's (I even integrated them with a string based mechanism into professional mixer cassette faders). But the dual mono thing drove me nuts and the physiological EQ curve I could realise with these was suboptimal.
I was very much German Studio Gear influenced at the time, so I changed to a 30 position switched resistor attenuator with very complex RC networks for the loudness compensation EQ derived from the original Eckmiller faders...
Ciao T
Hi,
Now, I tried to associate this number with anything and came up blanks. Care to illuminise me a little?
As for the rest, the problem on both sides is that actual fact and observation is replaced by Dogma and Belief. And most people are by far more comfortable with any false belief that results in the illusion that they understand what is going on and know something (preferably something others don't), than to honestly admit (to themselves at least) that something is going on and we know and understand feck-all about...
I personally find that the levels of my ignorance are positively staggering, but it causes me few headaches or gripes, except on a bad trip...
Ciao T
Now, I tried to associate this number with anything and came up blanks. Care to illuminise me a little?
As for the rest, the problem on both sides is that actual fact and observation is replaced by Dogma and Belief. And most people are by far more comfortable with any false belief that results in the illusion that they understand what is going on and know something (preferably something others don't), than to honestly admit (to themselves at least) that something is going on and we know and understand feck-all about...
I personally find that the levels of my ignorance are positively staggering, but it causes me few headaches or gripes, except on a bad trip...
Ciao T
How one would comment on using this kind of attenuators
http://www.thlaudio.com/indexE.htm
Attenuators/Switches: section, Amtrans
Do AMTRANS resistors really that good?
http://www.thlaudio.com/indexE.htm
Attenuators/Switches: section, Amtrans
Do AMTRANS resistors really that good?
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Hi,
The Amtrans look okay, however, gentlemen, if you want a "premium resistor", please consider this:
http://www.rhopointcomponents.com/images/econistor.pdf
http://www.rhopointcomponents.com/images/squaristor.pdf
I will happily entertain any suggestions of equal performance 5 cent resistors...
Ciao T
The Amtrans look okay, however, gentlemen, if you want a "premium resistor", please consider this:
http://www.rhopointcomponents.com/images/econistor.pdf
http://www.rhopointcomponents.com/images/squaristor.pdf
I will happily entertain any suggestions of equal performance 5 cent resistors...
Ciao T
For my present needs, an ideal would be 5W 500...1000 Ohms non-inductive resistor for high-end needs, to be used in the current NFB divider.
The RHOPOINT resistors seem to be low-wattage ones.
Hi,
If you need such low values and high power, try Mills MRA5. I use these where Rhopoint don't go...
Ciao T
If you need such low values and high power, try Mills MRA5. I use these where Rhopoint don't go...
Ciao T
Possibly they are a good choice. But, in general, one still can doubt, whether 1m of Nickel alloy wire in the signal path is better than 2cm of carefully deposited carbon-boron composition. Also having the Mills resistors at hand, I would check that their impedance modulus does not rise at 1MHz (better not to have this behaviour at NFB resistor position).
Ed it's just frustration, I'm sure Vishay would be interested in a configuration of their precision resistors that has .05% distortion (without gross mis-application). That is a pretty extraordinary claim.
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