Max, I might point out that there is a sort of a useful way to see, at a glance, the linearity of the op amp transfer function. You just get a TEK 577 (storage version)curve tracer and insert a TEK 178 op amp tester. Then you insert the IC and look at the transfer function. On the next input, I will show you of a typical example. Unfortunately, EVERYTHING that I made, even 40 years ago, did not deviate from a straight line with this test, only IC's and cheap power amps. Still, it shows something important, lost to many here.
Not really true. The LME family from National was designed for audio. The product manager for it at the time told me that National brought a real wizard in analog IC design out of retirement in Japan to make the best possible chips and the process guys worked for quite a while to optimize them.
JRC also has some audio specific opamps MUSES Official Website with prices reminiscent of the original LM301. ($50/ea at Digikey) They do have unusual aspects like copper leadframes etc.
I have been told by hardcore subjectivists that they sound good. . .
The newer versions MUSES8920,MUSES8920D,MUSES8920E (High Quality Audio J-FET Input Dual Operational Amplifier) | MUSES Official Website is back to reality with $5.00 pricing so it can't possibly be as good.
I suspect there are others out there, I just don't know. With surface mount packages becoming dominant swapping opamps and listening has may more variables.
Here in the post-1974 world, we can look on company websites.
Audio Amplifiers | Audio/Video Products | Analog Devices
Of course, those of us who have learned a few things since then can find the appropriate opamps for our applications without them being specifically labelled for "audio."
Would you kindly be more specific? This is too general statement. Almost no one uses THD or IM "testers" today, but everyone uses FFT analysis. If negative feedback created distortion not seen with FFT analysis how would it happen? Does it create random frequencies? Does it create non-periodic signals? Even if so, FFT would catch such frequency components, in smaller than real amplitude.
Okay,
So I have been shown to be incorrect and that there are audio specific opa's for audio. I should have brought up the monolithic power amplifiers but didn't. Now my question still stands, compare a modern opa to a discrete circuit and is there really a problem with using IC's in this regard or is that old comparisons that we seem to keep falling back to? Modern IC's vs brand new on the market discrete devices, not new old stock devices that can disappear at any time.
So I have been shown to be incorrect and that there are audio specific opa's for audio. I should have brought up the monolithic power amplifiers but didn't. Now my question still stands, compare a modern opa to a discrete circuit and is there really a problem with using IC's in this regard or is that old comparisons that we seem to keep falling back to? Modern IC's vs brand new on the market discrete devices, not new old stock devices that can disappear at any time.
I would have another question. Any electronic circuit adds something and changes the sound in its own way. Why not to replace Blowtorch with high quality stepped attenuator and resistor network? Stepped attenuator of 10k input impedance would have output impedance of 2.5k and less, when driven from low impedance signal source. This is not much more than Blowtorch's 1k output impedance and for practical listening volume setting like -20dB and less the output impedance of the 10k stepped attenuator would be lower than that of Blowtorch. So why not to avoid the electronic circuit that undoubtedly changes the sound in its own way (probably pleasant way?) to get something more neutral. Simpler is better, right?
Most test systems I know of have the DUT in a pretty static state when measuring. Even FFT won't easiily show a 1/2 second time constant on a resistor temp change.
Maybe we just need a test that shows what happens on longer time scales. Human hearing takes a finite time to process the stimulus. Is there any research on human response times to level changes etc?
Maybe we just need a test that shows what happens on longer time scales. Human hearing takes a finite time to process the stimulus. Is there any research on human response times to level changes etc?
I am more and more convinced that perfect signal transmission is the last thing audiophiles are seeking for.
Instead of that, loss of details is preferred. This loss of details is achieved by:
- higher background noise (tubes, vinyl records, tape hiss)
- non-linear distortion that rises noise floor for complex signals
Though higher background noise, and thus less real resolution, is generally preferred by audiophiles (tubes, groove noise, tape hiss), non-linear distortion must be thoroughly controlled to stay at pleasing side.
Instead of that, loss of details is preferred. This loss of details is achieved by:
- higher background noise (tubes, vinyl records, tape hiss)
- non-linear distortion that rises noise floor for complex signals
Though higher background noise, and thus less real resolution, is generally preferred by audiophiles (tubes, groove noise, tape hiss), non-linear distortion must be thoroughly controlled to stay at pleasing side.
You say that as if audio reproduction wasn't in the easiest 5% of jobs in electronics.
Gerhard
Depends on the high end designer and the particular "sound" they're trying to get; each has their own set of tricks to turn a box of gain into an effects box. It's trivially easy to make a clean amp- it takes some skill and imagination to make an effects box that hits the designer's target.
Mid-grade equipment is generally reliably transparent (assuming ears-only, of course), as is some high end gear when the designer truly does want a simple box of gain. IME, John's designs don't have an audible signature, for example.
This is an interesting question because it raises an issue for me about blowtorch o/p impedance.
I have found that amps very often sound better when driven by a low impedance.
I wonder how blowtorch manages to sound so good in systems with such high o/p impedance.
Is there something I'm missing here ?
mike
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