Ok. What you did is a bowl of cereal with ten tablespoons of sugar. Try the cereal with 1 tablespoon.
But very nice for those applications where the current draw is below the self-discharge of the battery. 🙂
Perhaps less relevant to a listening test, but useful when characterizing the components.
No. If the resistors all behave the same there is no output. You are welcome to work the math. The distortion from this test is lower than what a single resistor under test in a voltage divider with a perfect resistor would produce. It has the advantage of reciprocity and thus does not need a perfect reference resistor.
Scott,
Good point about harmonics vs frequency. So the thermal coefficient harmonics should decrease. That would highlight the non thermal distortion products. Of course only the poorer quality resistors (that I wouldn't be using) show any significant non-thermal distortion.
CC's won't though. Some in the same batch will compress a little more than others. They also behave differently in series than as terminators.
Just use ONE spoon of sugar on your cereal. It will taste good that way.
No CC's were used to harm any stray cats while generating this message.
Cats no....Hmm...
morinix, also done the test with low distortion reference resistors, where only carbon composition resistors were the distortion sources. If I find one I'll post it. The distortion profile stays the same. More interesting if I get around to it is the frequency variation.
Now wirewounds are not consistent enough to use 10 units. But the results for all the types have been out there for years and expanded on by others.
Ed, he want's the compressive distortion which is certainly fine, I just doubt there is more than a trivial amount in any sensible use.
The guitar guys made no sense they wanted to use 2W CC's to get "less" Johnson noise but still wanted the "sound".
Bear, Scott covered that earlier: essentially as tightly controlled as any other precision resistor you can buy. Bonus is they're all very nicely thermally coupled (and matched to themselves, if not absolutely), too.
Power demands in-circuit are far less, remember: the feedback network is much higher power in low-noise applications. (Which is conveniently external in the opamps in question!)
Power demands in-circuit are far less, remember: the feedback network is much higher power in low-noise applications. (Which is conveniently external in the opamps in question!)
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From the measurements of modern op-amps it is clearly not an issue, so what else do you want?
I can't hear anything. The difference between 0.00(lots)01 and 0.000(lots)01 THD escapes me.
The Hubble telescope (and it's successor) (and gravity waves) amaze me. The difference between a perfect Op-amp, a valve amp and a Perfect OP-amp don't do much....
Valves for instruments are great. Gibson valve amps with real springs in the reverb are great 😛
To argue 40 year old tech with modern kit is, well, a bit senseless 😱
Well, yes, from the present SOTA of measurements, I do agree.
However, I wonder if perhaps given the very small area of the resistive elements if it
was possible that there are thermal changes that are missed with certain types of measurements that only look at the output? Ok, maybe all that counts is the output... but how physically large are the resistors that are in the output circuits, and also is there any effect in resistive material (metal films?) when the element itself is getting down to "nano" dimensions??
Instantaneous changes? Is there a possible time constant working here? Is it being somewhat hidden by feedback? Probably not, but is there nothing here to consider at all?
Didn't someone say that certain surface mount resistors were so small that they were not working as desired? I seem to recall something along those lines...? Those are huge compared to what's on the chip itself...
The question that is on the table, is if the measurements tell all about what is heard or not. ABX/DBT or not, this remains the outstanding question. We're talking opamps.
I'm 100% for doing measurements and whatever tests are appropriate - I read another thread (was it mentioned here? not sure), now closed concerning an approach to DAC "output" that apparently involved some filtering tricks, but the important thing I'm getting at is that some here SY included offered to do testing if the hardware was supplied. I'm in favor of such explorations.
Ed has done some excellent testing/exploration on resistors (and other things). This sort of thing advances the understanding(s).
Let's do more of that, and less arguing and sniping that presumes what anyone thinks or wants or believes?
However, I wonder if perhaps given the very small area of the resistive elements if it
was possible that there are thermal changes that are missed with certain types of measurements that only look at the output? Ok, maybe all that counts is the output... but how physically large are the resistors that are in the output circuits, and also is there any effect in resistive material (metal films?) when the element itself is getting down to "nano" dimensions??
Instantaneous changes? Is there a possible time constant working here? Is it being somewhat hidden by feedback? Probably not, but is there nothing here to consider at all?
Didn't someone say that certain surface mount resistors were so small that they were not working as desired? I seem to recall something along those lines...? Those are huge compared to what's on the chip itself...
The question that is on the table, is if the measurements tell all about what is heard or not. ABX/DBT or not, this remains the outstanding question. We're talking opamps.
I'm 100% for doing measurements and whatever tests are appropriate - I read another thread (was it mentioned here? not sure), now closed concerning an approach to DAC "output" that apparently involved some filtering tricks, but the important thing I'm getting at is that some here SY included offered to do testing if the hardware was supplied. I'm in favor of such explorations.
Ed has done some excellent testing/exploration on resistors (and other things). This sort of thing advances the understanding(s).
Let's do more of that, and less arguing and sniping that presumes what anyone thinks or wants or believes?
Right, you can't hear anything. Your words. Which is fine. Not a problem.
However, the question is under what conditions have you not heard anything? That's a serious question.
Almost nobody here is willing to say.
I can speculate why that is, but I'm not interested in slinging mud.
I'm interested in getting to the bottom of what is a ROYAL PIA, that being that I've yet to hear two opamps that DO sound the same (I don't mean two of the same type and brand). There are some that do sound pretty darn close, maybe close enough so as to not really matter or make enough difference. This has been said.
But assuming that you or anyone else "can't hear anything". Then why pound this same drum over and over? Yes, yes, "measurements". I know. But anyone who has lived long enough and done audio long enough can remember full well when all sorts of bona fide experts proclaimed that the new-fangled solid state amps with "0.001" distortion all were inaudibly different, all had distortion products too low to hear, and were virtually perfect.
Turns out not so.
So, now the distortion product measurements have been cranked down another order of magnitude (maybe more??) and the same claims are made by bona fide experts. (sound familiar?)
And there was a majority of people then, as now that agreed with this, and came with pitchforks and tar to roust the infidels who (honestly) disagreed.
Why not try to explore NEW directions of study (like Simon7000 did with resistors, etc.) and see what as a group we can COME UP WITH that may just possibly REVEAL something - even if that something is that the measurements do NOT show any differences that we OUGHT TO BE ABLE TO HEAR??
Rather than beat the same old drum. Rather than that.
You can look at the AD8229 datasheet, from the schematic there are 2 - 3K thin film resistors that form a divider with an external gain resistor. The resistor thermal error appears directly at the output ~+-1ppm @ 10V, not bad for a few hundred atoms. BTW the 4 resistors in the output bridge tend to cancel each other out since most of the time the voltages are all equal.
EDIT - I have no idea why the G = 1 and G = 1000 errors are the same (which would indicate that there is no error from the resistors). So I can only say the 1 ppm @ 10V sets the max error. I might repeat the measurement though I did not do it in the first place. Try the AD620 I did do those measurements, using the actual referred to output error voltage disambiguates the data. The curvature is still on the order of low ppm. Though I fixed it on the AD621 (some is from contact potential TC).
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Bear, I don't know what to tell you, what Ed's work does is complement datasheets (as those distortion tests aren't exactly in there), whereas the very data you're looking for is in the datasheets of the opamps. I suppose one could make a bridge circuit of different opamps and see what the differences are, but that would quickly become a wild goose chase where we're looking for residuals in the PPM or smaller.
Yes, the proof is in the pudding, which IS the output. However the heck you get it.
So all those things you're ostensibly wondering about (i.e. in-chip resistor linearity) are baked into the opamps ultimate performance. Dimitry recently linked Bruce Hofer's powerpoint presentation on high-performance analog, which talks about thermal modulation among other topics. Comes recommended.
If you want to tell if XYZ opamp is first audible, then some very careful tests need to be made. But how do you reconcile talking about many opamps being good enough for SOTA measurement equipment and yet somehow audibly different? That points to absolutely needing a heroic experiment to divine.
Yes, the proof is in the pudding, which IS the output. However the heck you get it.
So all those things you're ostensibly wondering about (i.e. in-chip resistor linearity) are baked into the opamps ultimate performance. Dimitry recently linked Bruce Hofer's powerpoint presentation on high-performance analog, which talks about thermal modulation among other topics. Comes recommended.
If you want to tell if XYZ opamp is first audible, then some very careful tests need to be made. But how do you reconcile talking about many opamps being good enough for SOTA measurement equipment and yet somehow audibly different? That points to absolutely needing a heroic experiment to divine.
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They think they like the distortion sound of carbon and bakelite (there are better sounds).....never mind.
Dan.
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