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Old 25th February 2012, 08:29 PM   #2751
wahab is offline wahab  Algeria
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Quote:
Originally Posted by ThorstenL View Post
Hi,
So the SPL is around 80dB at 1m and probably lower than that at listening distance. The human hearing becomes more sensitive at these fairly low levels.

Speaker HD would arguably be low.
Also human listening is more linear at such levels , tympani
compression is low.
Quote:
Originally Posted by ThorstenL View Post
So it is not 0.1% THD, but over 0.5%, a difference of more than 14dB compared to your claim.

Can 0.5% THD with harmonic structure like you show be heard on an 80dB SPL pure tone? Yes, very likely.

Now can 0.1% almost pure 2nd HD be heard at 108dB SPL with pure tones?

Ciao T
Yes but it s audible with values as low as 0.1% , particularly
if there s significant H3 , H5.

One who is musician will notice the presence of a fifth
and a third very clearly, while a not musicaly trained ear will
still have the impression of a sound that sound...false !!....

The H2 and H4 are more subtle in that they are octaves
of the fundamental , but basicaly their effect , also audible
at relatively low level , is to add some kind of punch to the sound,
as would do an exciter.

The mix of all these even and odd harmonics render the sound
quite unpleasant.

All this is with a 1KHZ sine as signal , so all else being equal ,
this must be kept in this context as musical signals are a different
matter in respect of added harmonics tolerance and audibility.
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Old 25th February 2012, 09:11 PM   #2752
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Right, in case of musical signals intermodulation causes dirt, not Fourier analysis.
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The Devil is not so terrible as his math model is!
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Old 25th February 2012, 09:24 PM   #2753
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Quote:
Originally Posted by wahab View Post
Also human listening is more linear at such levels , tympani compression is low.
Yeah, but mechanical hysteresis of the ear-bones is prevalent.
The ear is a better sensor at medium-high average levels. Actually this is indirect reflected in any audiometry chart.

Last edited by SoNic_real_one; 25th February 2012 at 09:27 PM.
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Old 25th February 2012, 10:07 PM   #2754
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by bcarso View Post
What puzzles me is who might be left in the vast Harman empire who knows how to design non-switching amps. The company has been IMO on a downward spiral of truly ghastly proportions, with the occasional glimmer of hope here and there, since a CEO with no audio experience whatsoever took over, moved corporate HQ to Connecticut and replaced all of his direct reports. The company has since shed a plethora of talented people. Whatever issues one may have had with Sidney Harman, people used to say we could do a lot worse. They are being vindicated in that judgment! So it goes. Of course we have Bose and Monster et al. to compare to, which makes the situation seem less bad I suppose.
Looks like JA was impressed ...

"Harman Kardon's HK 990 is a powerhouse of an amplifier with, overall, superb measured performance. While high-quality outboard phono stages and D/A processors will give better measured performance than the HK 990's equivalents, there is no other sign of any aspect of its performance having been compromised to include so many versatile features. I am impressed."

óJohn Atkinson
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Old 25th February 2012, 10:12 PM   #2755
a.wayne is offline a.wayne  United States
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Default Harman Kardon HK 990, Direct Path, distortion (%)vs 1kHz continuous output power into

A power house for sure .....2 ohm ...
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Old 25th February 2012, 10:24 PM   #2756
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Hi,

Quote:
Originally Posted by wahab View Post
Yes but it s audible with values as low as 0.1% , particularly if there s significant H3 , H5.
Again, 0.1%3rd (or worse 5th) Harmonic at 80dB SPL can be readily audible with pure tones.

Your initial post made it seem that you claimed 0.1% THD of the 2nd Harmonics dominant spectrum you showed was readily audible with pure tones. Even at 80dB SPL I would somewhat doubt that.

Ciao T

PS, what is the HD level of your speakers?
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Old 25th February 2012, 10:45 PM   #2757
wahab is offline wahab  Algeria
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Quote:
Originally Posted by ThorstenL View Post
Hi,

Again, 0.1%3rd (or worse 5th) Harmonic at 80dB SPL can be readily audible with pure tones.

Your initial post made it seem that you claimed 0.1% THD of the 2nd Harmonics dominant spectrum you showed was readily audible with pure tones. Even at 80dB SPL I would somewhat doubt that.

Ciao T

PS, what is the HD level of your speakers?
I will do a test dedicated to even harmonics to have
some clues about it...

As for my speaker s HD content , i dont know since i ve no
accurate enough microphone to perform a valuable measurement.

I dont use DIY speakers , i just bought them used in a studio ,
for a mere 250 euros for the pair....

Monitoring systems - studio speakers. Welcome to the world of QUESTED

http://www.quested.com/data-sheets/H108.pdf

Last edited by wahab; 25th February 2012 at 10:51 PM.
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Old 25th February 2012, 11:04 PM   #2758
wahab is offline wahab  Algeria
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Quote:
Originally Posted by SoNic_real_one View Post
Yeah, but mechanical hysteresis of the ear-bones is prevalent.
The ear is a better sensor at medium-high average levels. Actually this is indirect reflected in any audiometry chart.
At what level is "medium" ??...

At high average level i suppose that you ll have to take account
of the very same ear-bones own resonnances that are distinct
of the listened signal, hence discrimination capability may not be as good.

For the test i did , it was about 80dB SPL , with THD contents
trimed from below 0.1% to 0.5% , wich render them clearly audible
thanks to the ear not being saturated by the fundamental.
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Old 26th February 2012, 12:31 AM   #2759
tvrgeek is offline tvrgeek  United States
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Status report on the DH-120 saga.
With the repairs done, it sounded OK. About where I started which is below par to the Rotels and Parasound. Parts came so I went to bench it and get good before measurements. One side I had only 25mA bias. The VAS CCS was not working correctly. Fixed that and changed the fixed resistors in the spreader to get a full 110mA on both sides. Adjusted the "symmetry" for equal swing on the scope. Depending on temp, this puppy is barely stable. It was OK at 90mA bias, but at 110, when cold it would ring about 900Khz on the positive side for a few seconds if you put in a 10K square wave at 1V p-p. Gain is not quite the same right to left, 19V on left, 20 on right with 1V RMS 20K sine wave. Full power Bandwidth seems to be above 30K with a 8 Ohm resistor load. It is less stable with no load. I put in the corrected gate resistors as per the changed outputs. Made it even touchier, but the square wave was a shade more square. Think I'll sleep on it and decide if I am going to continue beating the original design into submission, or if I should jump to the end game as modeled in SPICE and then fix the ugly realities I expect. Sitting here, I think I just came up with a way to get the gate resistors right on the sockets and not break them. This is not really an easy layout to work on.
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Old 26th February 2012, 01:17 AM   #2760
bcarso is offline bcarso  United States
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Quote:
Originally Posted by a.wayne View Post
A power house for sure .....2 ohm ...
I'll have to find out who did that.
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