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Old 27th December 2011, 05:38 AM   #201
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Hello All,
I run a Hk CIT II with early kT-90's.
I have run a few different preamps & sources; I have a HeathKit SP2 & have used other cit solid state preamps; the obviously 2nd harmonic rich Sp2 always won the listening time. Being an optical physicist I wanted the "clean" preamp to win but it simply didn't in front of the CITII. I still am looking to clean up the sound without losing whatever brings that dynamic alive, I hear it on the trailing edge of male vocals, close mike snare & in the"air" around tenor sax and trumpet lines.
But I digress, my main point was I just recently pulled some early Johnzer sealed 12 inch threee way's for some rectlinear III's which I am modding ( blown mid on one) with a modified focal7k011DB/tc90 pair. (previously used in a homemade 3 order x-over sub system)
The difference in performance from the CIT II under the vented woofer load was stunning. Now I really have to fix the preamp as it is coloring strongly past "raised voice talking level " 80-90dB.

I have heard quite few systems since my Uncle's AR3a/Marantz receiver set of the 1960's, I am always surprised none of them 30 dollars ->15000 ( within the limits of recording media) can reproduce the sound of live acoustic; Play a sax or bang an upright piano and surely any of you can hear delta.
What that delta is still not clear to me, but first order crossovers compared to third order crossovers seem to have a similar difference with first order more lifelike.
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Old 27th December 2011, 08:03 AM   #202
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vanderpol, your conclusions are interesting, but they are not very complete. 2'nd harmonic is tolerable, but real high fidelity reproduction does not add it deliberately. However, I suspect that less than 0.05% harmonic would be almost impossible to detect in normal listening. Every one of my designs is completely complementary push-pull, BUT I have heard some single ended systems that sounded pretty darn good, almost to to point of sounding like 'live acoustic'. You just can't judge without listening.
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Old 27th December 2011, 10:58 AM   #203
SY is offline SY  United States
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Quote:
Originally Posted by Wavebourn View Post
As were mentioned here several times, distortions that slip out of traditional measurements are of dynamic characted. That means, if you don't hear 10 Hz frequency, changes with such frequency still are audible as dirt.
Depends on how you define "traditional measurements." That sort of thing shows up as sidebands in spectral analysis (which is both common and trivial to do these days).
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Old 27th December 2011, 03:06 PM   #204
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SY, just how are we supposed to measure the sideband deviations with traditional spectral analysis? Do you imply that we could evaluate FM distortion this way? If so, please give me your procedure. Also, just because it may not be visible on a screen, does not mean that it could not be audible. It might be the limitation of the FFT resolution or the test equipment, I should think. AM distortion certainly is audible below what we see on an oscilloscope, normally, as a comparison.
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Old 27th December 2011, 03:18 PM   #205
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Hi John,
Yes I suppose one can say we never add harmonics on purpose but the truth is we may hear relative amplitude of odd/even harmonics and be senstive to this. That is what I think I am aiming for a "musical balance" down close to the noise floor, and perhaps under it...
Has anyone ever composed a table of the 1-4 odd and 1-4 even harmonics for say 10 amps/preamps? To me that would an interesting figure of merit.

I think another interesting measurement would a white/pink noise measurement; a fourier transform that transfer function, F(Noise out/Noise in)
might be very telling.

I think everyone would also agree that a single channel source is very different "sounding" then stereo. I suspect that the phase relationship of the odd order harmonics is what gives space to reproduced music; perhaps this why mono is "easy" to listen for long periods of time, again a straight forward measurement might be F(L+R Noise In/ Nout),in phase and F(L+R Noise In/ Nout), out of phase

Using these metrics I would be willing to bet a direct mapping of 70's transistor, 90's FET's, 50's push pull and modern amp designs would be differentable.

In closing check out
Brass instrument (lip reed) acoustics: an introduction
the mute/no mute is very interesting; wonder if a THD/IMD measurement would show any measurement of the non harmonic envelope under the harmonic structure

Lou
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Old 27th December 2011, 03:20 PM   #206
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Spectral resolution is pretty straightforward- with a typical computer setup, better than 1Hz is easy. The sidebands that result from FM or plain old amplitude distortion are pretty characteristic. $200 gets you nearly 100 kHz of bandwidth, better than -150dB noise floor, and better than 1Hz resolution.

This capability cost six figures when I was at Nicolet. I am still totally amazed at how easy and reliable modern implementations are.
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Old 27th December 2011, 03:27 PM   #207
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Vanderpol, what do you think that we do as audio designers? First of all, NOT ALL harmonics are the same in effect or annoyance. This has been stated in the 'Radiotron Designers Handbook' for more than 70 years, and their original estimates are amazingly similar to what we find today, especially in relative amplitudes, as to what we can detect and what to avoid when designing audio electronics.
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Old 27th December 2011, 04:51 PM   #208
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Stick a negative feedback and bias knob on the front panel, with good tweaking one could get ,

1. Class-a sound
2. Class-d sound ( dial back the bias, wack out the NFB)
3. Toob sound ( resistor box for damping control, dial back feedback/up bias )
4. Class-a/ab sound

An amp for everyone ...........
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Old 27th December 2011, 04:56 PM   #209
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Quote:
Originally Posted by SY View Post
Spectral resolution is pretty straightforward- with a typical computer setup, better than 1Hz is easy. The sidebands that result from FM or plain old amplitude distortion are pretty characteristic. $200 gets you nearly 100 kHz of bandwidth, better than -150dB noise floor, and better than 1Hz resolution.

This capability cost six figures when I was at Nicolet. I am still totally amazed at how easy and reliable modern implementations are.
could you elaborate more on your setup ..? what is an a typical PC setup.?
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Old 27th December 2011, 05:08 PM   #210
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Quote:
Originally Posted by SY View Post
Depends on how you define "traditional measurements." That sort of thing shows up as sidebands in spectral analysis (which is both common and trivial to do these days).
Traditional means static measurements using sinewave generators, notch filters, AC voltmeters. However, spectrum analyzer is the way to observe dynamic behavior, but you can't name and calibrate all possible dynamic flaws of all possible topologies, to define a new tradition of measurements.
And even if you do, how many would agree with your new standards? At least, Stereophile always has own opinions, independent on engineers'.
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