john curl said:
Well, at least the PIZZA-making procedure is pretty good!
- Tom Gootee
http://www.fullnet.com/~tomg/index.html
Hi all
pms'a interesting simulation should be treated carefully. The basic circuit started with - a basic diff amp with essentially no Re (0.1 ohm << internal Re at low currents). This is a weakly non-linear circuit! Applying signal at different levels will cause it to operate at different levels of distortion. THe spectrum comparison shows 1 kHz and 30 (33/34 kHz) signals at different levels in the two circumstances!
The interesting point I think is revealed by the measurements on actual amplifiers. But when feedback enclosing slower output transistors is applied, the input stages (i.e. diff amp) may overload (cut-off) if the signals are at relatively high levels.
John Curl - are you serious about oxygen-free copper?
What evidence is there that this has any effect whatsoever on audio quality? O2-free copper MAY have a lower resistivity. But that's it.
cheers
John
pms'a interesting simulation should be treated carefully. The basic circuit started with - a basic diff amp with essentially no Re (0.1 ohm << internal Re at low currents). This is a weakly non-linear circuit! Applying signal at different levels will cause it to operate at different levels of distortion. THe spectrum comparison shows 1 kHz and 30 (33/34 kHz) signals at different levels in the two circumstances!
The interesting point I think is revealed by the measurements on actual amplifiers. But when feedback enclosing slower output transistors is applied, the input stages (i.e. diff amp) may overload (cut-off) if the signals are at relatively high levels.
John Curl - are you serious about oxygen-free copper?
What evidence is there that this has any effect whatsoever on audio quality? O2-free copper MAY have a lower resistivity. But that's it.cheers
John
Re: Device and simple circuit simulations
Morricab,
Yes, we should really be looking at the threshold of audibility (you may want to scroll back to my post #1378). There I mentioned tests that showed that a very distinctive signal (2 KHz beeps) could hardly be detected 6 dB down in white noise - and that was when one was expecting it. Signals can be masked by noise! I would believe that signals 10 dB below noise and 4 - 5 dB below threshold-of-audibility would be quite inaudible, however related to anything. There was a test by a Scandinavian university but that was years ago and I unfortunately no longer have the report.
Your other very good points have been replied to equally well above.
Generally, one thing more: Oxygen-free copper? How oxygen-free? I tried to research this some time ago, and could not get any evidence from major wire manufacturers (such as Belden) that such exists, in the sense that all copper wire is oxygen free. The process of purifying copper precludes that. The comment was that to have even less oxygen than the usually quoted 0.0000?% would be such an expensive exercise that it would be prohibitive. At any rate the hi-fi industry comprised such a small sector of the market that probably no one would even consider making "special copper" for them. This apart from the point that it was chemically ridiculous to suppose that it would play any role in audio.
That was what my quieries yielded, and I have since ignored the matter.
Edit: Typo
morricab said:
Morricab,
Yes, we should really be looking at the threshold of audibility (you may want to scroll back to my post #1378). There I mentioned tests that showed that a very distinctive signal (2 KHz beeps) could hardly be detected 6 dB down in white noise - and that was when one was expecting it. Signals can be masked by noise! I would believe that signals 10 dB below noise and 4 - 5 dB below threshold-of-audibility would be quite inaudible, however related to anything. There was a test by a Scandinavian university but that was years ago and I unfortunately no longer have the report.
Your other very good points have been replied to equally well above.
Generally, one thing more: Oxygen-free copper? How oxygen-free? I tried to research this some time ago, and could not get any evidence from major wire manufacturers (such as Belden) that such exists, in the sense that all copper wire is oxygen free. The process of purifying copper precludes that. The comment was that to have even less oxygen than the usually quoted 0.0000?% would be such an expensive exercise that it would be prohibitive. At any rate the hi-fi industry comprised such a small sector of the market that probably no one would even consider making "special copper" for them. This apart from the point that it was chemically ridiculous to suppose that it would play any role in audio.
That was what my quieries yielded, and I have since ignored the matter.
Edit: Typo
Guys, please give it up. Oxygen free copper is a well known process that many high end cable companies use. I should use any less? Oxided copper is OK? Impure copper is OK? Poorly handled copper is OK? Perhaps for amateurs. (I know, this will get me into trouble, sorry about that. I just don't know how to express myself any better. )
Andy_C:
It's important that the results of a given circuit not be generalized to all circuits regarding how feedback affects them. Also, they present results with distortion going down to 200 dBc, yet the models they use are very primitive. The SPICE models take into account many more different types of errors than the models Boyk and Sussman use, yet the SPICE models fall apart at much higher levels than that. So their data can be considered conceptually useful, but one cannot expect to get actual numbers that are anywhere near that in real circuits. Same for the SPICE simulations too. I took my graphs down to 140 dBc but it's extremely unlikely that the data down there are accurate.
Yes, especially if you consider that the time series that go to FFT
are created by stepwise numerical integration and RK-Iteration
to remove nonlinearities from the final G-matrix. I would not trust
any solver at -200 dBc.
Often it's hard enough to make it converge at all.
regards, Gerhard
It's important that the results of a given circuit not be generalized to all circuits regarding how feedback affects them. Also, they present results with distortion going down to 200 dBc, yet the models they use are very primitive. The SPICE models take into account many more different types of errors than the models Boyk and Sussman use, yet the SPICE models fall apart at much higher levels than that. So their data can be considered conceptually useful, but one cannot expect to get actual numbers that are anywhere near that in real circuits. Same for the SPICE simulations too. I took my graphs down to 140 dBc but it's extremely unlikely that the data down there are accurate.
Yes, especially if you consider that the time series that go to FFT
are created by stepwise numerical integration and RK-Iteration
to remove nonlinearities from the final G-matrix. I would not trust
any solver at -200 dBc.
Often it's hard enough to make it converge at all.
regards, Gerhard
Re: Re: Device and simple circuit simulations
John,
Not to hi-jack this thread, but ... I repeat: How oxygen-free?
Your very apt post slogan says "Condemnation without examination is prejudice". True.
Now if I have examined, and found no evidence where one would expect to find same, but found evidence to the opposite, again where one would expect to find such evidence .... am I not then entitled to - well, at least - doubt? (Decidedly, the process does not appear to be so "well known", except in promotional literature ... )
john curl said:
Johan Potgieter said:
John,
Not to hi-jack this thread, but ... I repeat: How oxygen-free?
Your very apt post slogan says "Condemnation without examination is prejudice". True.
Now if I have examined, and found no evidence where one would expect to find same, but found evidence to the opposite, again where one would expect to find such evidence .... am I not then entitled to - well, at least - doubt? (Decidedly, the process does not appear to be so "well known", except in promotional literature ... )
Andy_C:
>Sounds like you've done some studying of SPICE internals, Gerhard.
> I used to work for a simulator company, but I was pidgeonholed into UI work.
When I studied electronics, our CAD prof forced us to implement all
the relevant algorithms ourselves before we were given the spice 2g? sources.
That was Fortran time with card punches and line printers.
We had a book written by a guy named Director that could have been excellent
but that had so many misprints that it was close to useless without
a provided bug list.
The biggest thing I wrote at this time was a routine that plugged
bipolar transistors into a G-matrix ( apart of an 8080 cross assembler
and an 8080 floating point package.)
Nowadays I use Agilent ADS or Genesys (or LT-Spice at home), and I'm thankful,
appreciating the things that are buried in this software.
regards, Gerhard
>Sounds like you've done some studying of SPICE internals, Gerhard.
> I used to work for a simulator company, but I was pidgeonholed into UI work.
When I studied electronics, our CAD prof forced us to implement all
the relevant algorithms ourselves before we were given the spice 2g? sources.
That was Fortran time with card punches and line printers.
We had a book written by a guy named Director that could have been excellent
but that had so many misprints that it was close to useless without
a provided bug list.
The biggest thing I wrote at this time was a routine that plugged
bipolar transistors into a G-matrix ( apart of an 8080 cross assembler
and an 8080 floating point package.)
Nowadays I use Agilent ADS or Genesys (or LT-Spice at home), and I'm thankful,
appreciating the things that are buried in this software.
regards, Gerhard
Bob Cordell said:
Hmmm.....with a dominant pole frequency of 4kHz, 34dB is lost at just 200kHz. Even without an output coil, I think it would be possible to go higher than that.
I think the physical construction/layout of the JC-1 would probably have just as great a bearing here - two long rows of RET's on opposite sides of a rather large case.
Cheers,
Glen
Re: Re: Re: Device and simple circuit simulations
Hi Johan,
(Thanks, very much, for your earlier response to me, by the way.)
I had never given the "oxygen-free copper" a second thought, assuming it was only audiophool territory. But now I'm wondering if maybe it is simply something fairly trivial, which just occurred to me: We know that various oxides can form in the surface layers of metals that are exposed to air, and that their presence can affect the electrical properties (especially for higher frequencies I would guess, where skin-effect is more predominant). So, perhaps the "oxygen-free" copper is merely copper that has been coated with something like lacquer before it has been exposed to any O2-containing air, or, alternatively, at least almost-immediately after being made into wire. I'm just guessing, about all of this. But at least it would be a simple explanation, if correct. And it's easy-enough to imagine the marketing hype being developed, to tout a little extra care, or slightly-more-demanding processing, during the wire manufacturing, especially if it could be, in any way, construed to have improved the quality, or to be "high-end".
I hope that someone who really knows will comment.
- Tom Gootee
http://www.fullnet.com/~tomg/index.html
Johan Potgieter said:
Hi Johan,
(Thanks, very much, for your earlier response to me, by the way.)
I had never given the "oxygen-free copper" a second thought, assuming it was only audiophool territory. But now I'm wondering if maybe it is simply something fairly trivial, which just occurred to me: We know that various oxides can form in the surface layers of metals that are exposed to air, and that their presence can affect the electrical properties (especially for higher frequencies I would guess, where skin-effect is more predominant). So, perhaps the "oxygen-free" copper is merely copper that has been coated with something like lacquer before it has been exposed to any O2-containing air, or, alternatively, at least almost-immediately after being made into wire. I'm just guessing, about all of this. But at least it would be a simple explanation, if correct. And it's easy-enough to imagine the marketing hype being developed, to tout a little extra care, or slightly-more-demanding processing, during the wire manufacturing, especially if it could be, in any way, construed to have improved the quality, or to be "high-end".
I hope that someone who really knows will comment.
- Tom Gootee
http://www.fullnet.com/~tomg/index.html
Tom, you know what 'Google' is don't you? You also know the Wikipedia? Why don't you do a little checking about 'oxygen free copper' before you speculate. I say this in the best sense, since many here speak out before checking facts.
Actually, I use linear crystal 6 9's pure silver teflon coated wire in the Blowtorch preamp. It is VERY expensive and we have to break it in electrically in advance for weeks, and then again after we cut and solder it in. I have heard the difference between identical units, one made of the best oxygen free copper wire, and the silver wire. The copper wire sounds OK, but slightly softer.
Ask Bear on this website, if you have any questions.
Actually, I use linear crystal 6 9's pure silver teflon coated wire in the Blowtorch preamp. It is VERY expensive and we have to break it in electrically in advance for weeks, and then again after we cut and solder it in. I have heard the difference between identical units, one made of the best oxygen free copper wire, and the silver wire. The copper wire sounds OK, but slightly softer.
Ask Bear on this website, if you have any questions.
john curl said:
Everyone knows that audible softness can be more than amply compensated for by avoiding telfon wire, aligning the preamplifier 15% to the horizon and turkey slapping it continuously during the breaking in preriod.
PS
I hope your PCB's use oxygen free copper too.
Cheers,
Glen
john curl said:
John,
Nobody doubts your preference, but the fact remains that Johan seems to have actually researched this, and stated his findings. Now, he may have overlooked something, and if you have a source of information to support or counter his findings, that would be great. If not, then maybe we shall conclude that "O2-free" preference is based on personal opinion? Which is OK, and then we can move on.
Jan Didden
john curl said:
It is not easy to see it on instrument screen. Simulation is pretty helpful, it enables to subtract output - (input x exact multiple of "steady state" transfer coefficient). The subtraction must be tuned precisely and then you can see what feedback has to control
. This is "optimal class B bias" (some 47mA) for lowest distortion NUMBER. Though distortion seems low (like 0.02%), its spectrum is horrible. No real NFB can cure it.