"The sum of the square roots of any two sides of an isosceles triangle is equal to the square root of the remaining side."
Napoleon is said to have made to Robert Fulton: "What sir, you would make a ship sail against the wind and currents by lighting a bonfire under her decks? I pray you excuse me. I have no time to listen to such nonsense."
He thought Fulton was trying to trap him.
(actually, Napoleon funded Fulton's first attempt to build a sub)
(actually, Napoleon funded Fulton's first attempt to build a sub)
I wasn't arguing with his enthusiasm, but his statements. Does his physics degree mean nobody is allowed to disagree with him? That is not the way most physicists see things.john curl said:
Maybe you have seen a different version of the article. In the linked version he doesn't actually say what the problem was, and how he fixed it. He just makes some inaccurate statements about phase shift oscillators (e.g. that a not-quite oscillating circuit maintains a flat frequency response), and compares them with an ordinary amplifier. He doesn't seem to distinguish between capacitors carefully chosen to create a phase shift and capacitors carefully chosen not to create a phase shift.
It is conceivable that women's hearing is different from men, and they may be sensitive to different degrees of distortion. Your anecdote seems to confirm the importance of careful measurement and good theory to explain what people think they are hearing, because our ears are easily fooled.
Campbell pointed out that HIS phase shift oscillator was V1 and V2 of his input tubes, and V3, one of the output tubes. P5 middle top.
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Well I have to confess, I have TRIED Scientology, and it worked for me, as well.
I shared an office at Ampex Research with a guy who taught it. He put me on an E meter, one day. I was impressed. However, I elected not to go in that direction. AND I do not particularly like the means and methods of the group, and I don't consider it a religion.
I shared an office at Ampex Research with a guy who taught it. He put me on an E meter, one day. I was impressed. However, I elected not to go in that direction. AND I do not particularly like the means and methods of the group, and I don't consider it a religion.
Actually very few people stop at BS in physics, they are virtually unemployable.
A "cult" is whatever religion you don't believe in. But whatever, they call themselves a church, the IRS allows them to be tax exempt, and thus any discussion is outside the rules of the forum.
Thermal/memory distorsions in amplifier input stages
With reference to ( Memory Distortion Philosophies - Part 1 : Theory )
A good candidate to proove the (non-)existence of thermal/memory distorsion of a standard diff input stage is the Schlotzaur voltage follower because bias conditions of its input stage and its output stage can be set independently.
Its best perfomances are attained when having an input stage made of a standard LTP loaded by a CCS and an output stage made of a common collector loaded by a CCS. Input and output stage can have different power supplies.
Using no load at the output, if thermal/memory distorsion occurs in the input stage with varying signals, it is logical to say that varying DC working conditions when fed with a fixed signal would show different harmonic distorsion spectra, implying different voltage transfer functions.
I obtain the following results, expressed as distorsion increases in dB, using a 1 kHz / 4 Vrms sine input signal with a sophisticated Schlotzaur circuit as described above (output stage power supply fixed at 30 V)
We see that more than doubling the current, from 2*0.4 mA to 2*0.85 mA, or increasing the power supply voltage by 6 V, from 24 V to 30 V, barely affect the distorsion components and this, with a signal voltage equal to two to four times the maximum input voltage of power amps. The bias and voltage variations during the test are far larger than those which ever occur in the real life of differential input stages of power amps. No significative misbehaviour which could be interpreted as thermal or memory distorsions has been shown.
With reference to ( Memory Distortion Philosophies - Part 1 : Theory )
A good candidate to proove the (non-)existence of thermal/memory distorsion of a standard diff input stage is the Schlotzaur voltage follower because bias conditions of its input stage and its output stage can be set independently.
Its best perfomances are attained when having an input stage made of a standard LTP loaded by a CCS and an output stage made of a common collector loaded by a CCS. Input and output stage can have different power supplies.
An externally hosted image should be here but it was not working when we last tested it.
Using no load at the output, if thermal/memory distorsion occurs in the input stage with varying signals, it is logical to say that varying DC working conditions when fed with a fixed signal would show different harmonic distorsion spectra, implying different voltage transfer functions.
I obtain the following results, expressed as distorsion increases in dB, using a 1 kHz / 4 Vrms sine input signal with a sophisticated Schlotzaur circuit as described above (output stage power supply fixed at 30 V)
Code:
[SIZE=2]varying the current of the CCS,
power supply constant at 30 V
H2 H3 H4 H5 H7
sine gen disto -130.5 -130 133 -132 -132
2 * 0.25 mA 3 1 0 0 0
2 * 0.40 mA 0.5 0 0 0 0
2 * 0.85 mA 0 0.5 0 0 0
2 * 3.00 mA 2 0 0 0.5 0
Keeping the current constant at 2 * 0.85 mA
but varying the power supply voltage
H2 H3
12V +7 +1
18V +2 0
24V +0.5 0
30V +0.5 0[/SIZE]We see that more than doubling the current, from 2*0.4 mA to 2*0.85 mA, or increasing the power supply voltage by 6 V, from 24 V to 30 V, barely affect the distorsion components and this, with a signal voltage equal to two to four times the maximum input voltage of power amps. The bias and voltage variations during the test are far larger than those which ever occur in the real life of differential input stages of power amps. No significative misbehaviour which could be interpreted as thermal or memory distorsions has been shown.
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Well Scott, I seem to have been given employment for the last 45 years. Charles Hansen, as well. A first degree in physics is a great tool to develop new audio products.
Ploying a trade as a research physicist? I don't think so. You both spend a lot of time throwing stones at some very basic principles, how about backing it up with some experimental physics.
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It might be that that getting 'more' academic education, such as a PhD in physics, 'might' inhibit our creativity. I like to keep an open mind. I have been studying engineering-physics all my life, since graduation. I sure that I put more time and energy into it than most.
I am now watching a documentary about Fractal mathematics, and Dr. Mandelbrot was once being attacked very much like I find many people's ideas are attacked here. Least we forget!
You should recognise my avatar after that then John 😉 Fractal mathematics is facinating, so many things seen in nature tend to pop up in fractal graphics, and all just from a simple formula.
Tony.
Tony.
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