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Old 31st January 2013, 12:02 PM   #33881
DF96 is offline DF96  England
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Interesting! A sharp filter causes the appearance of ringing on a sharp transient, not by adding anything but by removing the higher frequencies which would otherwise cancel the appearance of ringing. So is it the phase shifts below the stopband whch were heard, or the absence of expected components above the stopband which were then misinterpreted by the ear/brain as the presence of transients?
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Old 31st January 2013, 12:13 PM   #33882
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Interesting question
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Old 31st January 2013, 01:00 PM   #33883
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Quote:
Originally Posted by RNMarsh View Post
Regarding roll-off frequencies ---> group-delay is still important to keep under a certain threshold. Dean Jensen (Jensen Transformer founder and designer) made his fame by winding his transformers for low group-delay distortion (esp. at low end).... little known at the time. But, bares repeating from time to time. especially when talking about filters. CD and the filters used are not always minimum group-delay and can/do exceed audible thresholds. It is also one to test for as a complete end-to-end system. Thx-RNMarsh
And yet, when a zip cord is used between a low impedance source and a wildly varying low impedance load, the group delay caused by the transmission line effects are ignored.

Do you have any idea what level of delay Dean found and corrected for?
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Old 31st January 2013, 01:23 PM   #33884
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There is a lot to explore, about this bandwidth limitation question. There can be some side effects depending of the enclosures used for listening comparisons, by example. If they are not time aligned, it is possible a low pass filter add some phase shift with correct (or worsen) the group delay in this particular circumstance ?
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Old 31st January 2013, 01:24 PM   #33885
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Originally Posted by jan.didden View Post

Of four participants, one stepped out because he admitted not hearing any difference. The remaining three, yours truly among them, all identified correctly the two different situations but inverted: we thought that the situation with the filter switched in sounded the best! We also had similar descriptions of that 'best' situation: brighter, more attack, more transients. As I said, humbling.
I would rather say understandable - you have used a poor audio system for your test. 95% or maybe even more audio systems are poor, including so-called highend.
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Old 31st January 2013, 01:50 PM   #33886
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Originally Posted by vacuphile View Post
Nobody has ever been able to hear ultrasonic, sort of definitional.
Ultrasound - Wikipedia, the free encyclopedia

Humans

The upper frequency limit in humans (approximately 20 kHz) is due to limitations of the middle ear, which acts as a low-pass filter. Ultrasonic hearing can occur if ultrasound is fed directly into the skull bone and reaches the cochlea through bone conduction without passing through the middle ear.[3]


3. Corso, J. F. (1963). "Bone-conduction thresholds for sonic and ultrasonic frequencies". Journal of the Acoustical Society of America 35 (11): 1738–1743. Bibcode 1963ASAJ...35.1738C. doi:10.1121/1.1918804.
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Old 31st January 2013, 01:53 PM   #33887
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after new listening tests of the buffered AD797 I find this opamp very, or I would say extremely transparent, with great resolution of highs and details, and tight solid bass. In the past I have probably not implemented it well.
I would like to return to this post. After a week of listening tests, I would like to emphasize that the preamp based on AD797 with buffered output sounds great. It is extremely transparent with fantastic resolution and in the same time it is not aggressive. I mostly listen to classical philharmonic orchestra music when evaluating audio component. DGG Beethoven symphonies sets conducted by Harnoncourt and Gardiner are great through this opamp. No muffling, no blending, no rounding and also no aggressiveness. Hats off.
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Old 31st January 2013, 01:54 PM   #33888
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Jan, my Slot book show this info between pages 50-56.
Graph on p. 52.
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Old 31st January 2013, 01:55 PM   #33889
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Originally Posted by Esperado View Post
"But the fact that the listeners preferred full-range sound, if undistorted, had now been proved. "

OMHO, i prefer my speakers without tweeters (horn up to 16KHz, time aligned) but i prefer my electronic as fast as possible, and, as i said, a bandwidth up to 200Khz for my amp, and no brickwall for my CD. Hard to explain.
Perhaps the physical processes responsible for the roll-off at the speaker end produce different types of distortions/alterations than the high freq distortion produced by the the various electronics.

Last edited by AudioLapDance; 31st January 2013 at 02:08 PM.
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Old 31st January 2013, 02:05 PM   #33890
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I just found this nifty PowerPoint presentation that goes over some of the basics:

11.1 Fundamental Concepts
11.2 High-Frequency Models of Transistors
11.3 Analysis Procedure
11.4 Frequency Response of CE and CS Stages
11.5 Frequency Response of CB and CG Stages
11.6 Frequency Response of Followers
11.7 Frequency Response of Cascode Stage
11.8 Frequency Response of Differential Pairs
11.9 Additional Examples

www.ee.ucla.edu/~brweb/teaching/ch11_new.ppt


Lots of good tidbits from an electronics course:

Index of /~brweb/teaching
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