dhaen said:This is much the same argument as that of interconnects.
The recording and broadcast industries pass the signals we listen to through vast lengths, with no apparent loss.
However, I'm not going to say that interconnect and opamp quality is irrelivant. I believe many percieved differences depend on local conditions.
I have used TLO74's for over a decade as unity gain buffers. I cannot hear the difference between those and NE5532's in this application IE a well laid out PCB with quiet linear PSU, balanced audio inputs and outputs, and metal case.
Now, whether there would be a difference in a CD player, where some gain was used to use it as a Sallen-Key or Butterworth filter, and loads of digital and RF mush around, is too complex to analyse.
Well said. I would extend this argument to all other passive and active components as well. One man's floor is another man's ceiling.
Jan Didden
I think one goal should be to not make a signal any worse than it already is.
That way it would make sense to use quality OP-AMPs, even when our program material went through heaps of crappy ones before.
Regards
Charles
That way it would make sense to use quality OP-AMPs, even when our program material went through heaps of crappy ones before.
Regards
Charles
dhaen :
TL074 has its limitations. It isn't too bad for high impedance low current circuits with low gain, maybe a bit noisy for today FET standards, but try to use it as a balanced line driver to put a 1Khz square wave on 30-150 meters of shielded twisted pair wire and look at the actual waveform [a NE5532 or even a cheap LM833 performed flawless on the same test]
In the other hand, I've looked inside some mixing consoles up to $10.000 and what I found was TL072 stuff, lots of polaryzed electros for unpolarized applications, 5% resistors and some NE5532
TL074 has its limitations. It isn't too bad for high impedance low current circuits with low gain, maybe a bit noisy for today FET standards, but try to use it as a balanced line driver to put a 1Khz square wave on 30-150 meters of shielded twisted pair wire and look at the actual waveform [a NE5532 or even a cheap LM833 performed flawless on the same test]
In the other hand, I've looked inside some mixing consoles up to $10.000 and what I found was TL072 stuff, lots of polaryzed electros for unpolarized applications, 5% resistors and some NE5532
Horses for courses...
Oh no, I wouldn't dream of it
That's what DRV134's were made for 😉
Eva said:
Oh no, I wouldn't dream of it
That's what DRV134's were made for 😉Null test:
I would prefer to evaluate the resulting difference signal
with a head phone.
I did this null test about ten years ago by an adjusted precision
differential amp and measured the output the with the scope.
Two drawbacks:
-It was difficult to adjust not only the gain but also the phase shift
correctly.
-The measured results just gave some number.
I don't know why I did not have the idea to listen to this
signal with the head phone. But from theory I would expect
that you will the old orignal signal at a massively suppressed
level and the distorsions without suppression. This should really directly give a audiophonic impression about the flaws of the design.
I' ll keep in mind!! 🙂
This might also give your ears some idea, to calibrate tehmselfes for the double blind test 😀
I would prefer to evaluate the resulting difference signal
with a head phone.
I did this null test about ten years ago by an adjusted precision
differential amp and measured the output the with the scope.
Two drawbacks:
-It was difficult to adjust not only the gain but also the phase shift
correctly.
-The measured results just gave some number.
I don't know why I did not have the idea to listen to this
signal with the head phone. But from theory I would expect
that you will the old orignal signal at a massively suppressed
level and the distorsions without suppression. This should really directly give a audiophonic impression about the flaws of the design.
I' ll keep in mind!! 🙂
This might also give your ears some idea, to calibrate tehmselfes for the double blind test 😀
Maybe It would be a good idea to load the 10 opamps by setting them each to a gain of 2 and then cut the output of each one in half with a voltage devider on the output
If the voltage dervider used something a 22k resistor on the output and then another 22k resistor to ground this would provide 44k load on each opamp and also provide a bit of source impedance for the next stage. This way each opamp has to do some work 😉 I suspect opamps number 2 to 9 in the origanal test are having a nice holiday
runing at unity each with an input and output buffer! 😀
Maybe loading will give more of a real world test to the opamps (times 10) 😉
Billy
If the voltage dervider used something a 22k resistor on the output and then another 22k resistor to ground this would provide 44k load on each opamp and also provide a bit of source impedance for the next stage. This way each opamp has to do some work 😉 I suspect opamps number 2 to 9 in the origanal test are having a nice holiday
runing at unity each with an input and output buffer! 😀 Maybe loading will give more of a real world test to the opamps (times 10) 😉
Billy
Interesting idea. But 44K is something of a holiday itself. Maybe 4.7K would get us closer to what the opamps are capable of driving. And they wouldn't add as much noise.
I thought that was the reason 'nonbelievers' gave for the *deeper* soundstage of tubes 🙂
Collapsing the residual CD soundstage to one foot requires more absolute deterioration of the source signal than to create a much more noticeable effect on the imaging of a high quality analog recording.
thor, depends on who you ask. The diehard analogists think that CD doesn't have any depth to begin with. 😉
Noise is a funny thing- as one possible analogy, think only of the miraculous properties of dither in quantized systems...
Noise is a funny thing- as one possible analogy, think only of the miraculous properties of dither in quantized systems...
Hello -
First of all, my hat's off to Circlotron. Performing experiments like that are *exactly* how progress gets made in making better sounding audio gear.
However, I would tend to disagree with his conclusion and am also surprised that everyone else posting agreed with his conclusion. To me the interesting thing is this -- he *heard* a difference!
To me this is very interesting. Here is a person that (as far as I can tell from reading his postings) believes that adding the op-amps won't make any difference, but then he hears a difference when he actually tries the test.
Now I don't know all of the details of the experiment, but he posted enough for me to know that this was not the most sensitive experiment he could have performed. And yet he still heard a difference!
Best regards,
Charles Hansen
First of all, my hat's off to Circlotron. Performing experiments like that are *exactly* how progress gets made in making better sounding audio gear.
However, I would tend to disagree with his conclusion and am also surprised that everyone else posting agreed with his conclusion. To me the interesting thing is this -- he *heard* a difference!
To me this is very interesting. Here is a person that (as far as I can tell from reading his postings) believes that adding the op-amps won't make any difference, but then he hears a difference when he actually tries the test.
Now I don't know all of the details of the experiment, but he posted enough for me to know that this was not the most sensitive experiment he could have performed. And yet he still heard a difference!
Best regards,
Charles Hansen
Actually I was expecting it to make a very *big* difference so I could justify turning up my nose at opamps. But when it only made a very small difference - one that I could hear only after 10 minutes of listening - that's when I was surprised.
The fact that it didn't do what I was expecting to happen makes me think the effect is real, though slight.
The fact that it didn't do what I was expecting to happen makes me think the effect is real, though slight.
Great experiment! I wonder, though, if someone with 20/20 hearing (so to speak), would hear a bigger difference?
JF
JF
The fact that Circlotron heard a difference means that he has trained his ears well, just as a blind person trains their fingertips to distinguish Braille. I think if he had a properly set up (i.e., "tweaked") high resolution system he would have heard a bigger difference.
Let me give an example that illustrates two points pertinent to Circlotron's test. When we were selecting an input switch one time we did a careful comparison between a small-signal relay with gold plated contacts and a solid silver contact rotary switch. The test was done by inserting the DUT in the "hot" conductor of the interconnect going to the power amp.
We made a fixture that had the ground of a rhodium-plated female RCA soldered directly to the ground of a rhodium-plated male RCA. The "hot" lead of the control fixture was connected by two short wires soldered together. Duplicate fixtures were made with the DUT soldered in place between the two wires in the "hot" lead. This allowed us to hold everything constant when comparing to the control fixture, including the number of solder joints, et cetera.
The silver contact rotary switch produced almost no change in sound whatsoever. Perhaps a 1% loss of resolution, and no change in tonal balance. When we first connected the gold-plated relay, we were shocked to find that it sounded *better* than the "bypass" control fixture. This of course made no sense. How could inserting a passive device make an improvement?
So we spent about 30 minutes "tweaking" the system. We oriented the AC power cords to get the minimum leakage current on the chassis, we put different "footer" devices under the components, we double checked the speaker toe-in, et cetera.
Then when we repeated the test, we could now hear that the gold-plated relay was actually adding a slight but noticeable brightness that created a "halo" effect around each instrument. It was actually appealing sounding when played through the lower resolution, un-tweaked system. But in the higher resolution, tweaked system you could hear the problems it was creating.
Best regards,
Charles Hansen
Let me give an example that illustrates two points pertinent to Circlotron's test. When we were selecting an input switch one time we did a careful comparison between a small-signal relay with gold plated contacts and a solid silver contact rotary switch. The test was done by inserting the DUT in the "hot" conductor of the interconnect going to the power amp.
We made a fixture that had the ground of a rhodium-plated female RCA soldered directly to the ground of a rhodium-plated male RCA. The "hot" lead of the control fixture was connected by two short wires soldered together. Duplicate fixtures were made with the DUT soldered in place between the two wires in the "hot" lead. This allowed us to hold everything constant when comparing to the control fixture, including the number of solder joints, et cetera.
The silver contact rotary switch produced almost no change in sound whatsoever. Perhaps a 1% loss of resolution, and no change in tonal balance. When we first connected the gold-plated relay, we were shocked to find that it sounded *better* than the "bypass" control fixture. This of course made no sense. How could inserting a passive device make an improvement?
So we spent about 30 minutes "tweaking" the system. We oriented the AC power cords to get the minimum leakage current on the chassis, we put different "footer" devices under the components, we double checked the speaker toe-in, et cetera.
Then when we repeated the test, we could now hear that the gold-plated relay was actually adding a slight but noticeable brightness that created a "halo" effect around each instrument. It was actually appealing sounding when played through the lower resolution, un-tweaked system. But in the higher resolution, tweaked system you could hear the problems it was creating.
Best regards,
Charles Hansen
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