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Old 15th June 2007, 11:45 PM   #101
AKSA is offline AKSA  Australia
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Lineup,

Nice to have some explanation from the Variac, who I thought was very moderate, operating well below mains on this occasion.....

Thank you for your comments, yes, a couple of children, Soraya 21, and Alessandra, 19. The eldest is a girl racer, a real petrol head, like me.

P-A,

You must be tolerant of your own countryman. Lineup and Carlos both add something and dilute the objectionable egos which are a part of all forums!

Tony,

Possibly. However, it's innocent enough. BTW, how is it that your written English is magnificent, right down to the slang - I have a friend married to a high class Mexican lady and her English is better than most Australians. Spanish is reputedly the best language of all to express strong emotion; English is much more functionally oriented, without the intense color of your language. This clever lady is now a high powered executive here in Melbourne. I conclude that you have enjoyed a wonderful education, and we are privileged to talk with you, particularly if you like Pass gear.

On AKSAs,

This amp was deliberately designed to very slightly color the sound with typical levels of 0.04% H2 and H3. The principle was the known psychoacoustic masking of these harmonics on the higher order harmonics spuriously created in most SS, feedback amplifiers. The design is very, very simple, but no one looking at the circuit has ever been able to figure out precisely how it's been achieved, which has protected the IP better than any patent. But the amp definitely sounds a bit like a tube amp, but with the slam and sheer grunt of solid state, something the tube amps struggle to achieve.

I'm still selling them, but my latest amp has gone all out to reduce distortion to vanishingly low levels. I do not have figures, as I don't own an AP1, but THD should now be below 0.005% at all levels to full power. Nested feedback, phase lead and superlinear circuit blocks have brought improvement in resolution, with much more spatial information and almost zero congestion with heavy orchestral works, focussing deficiencies squarely on the speaker and source.

P-A, I've started using surface mount; the DMMT5401 supermatched pair for the LTP. You must be very careful not to draw breath while mounting them - they are so light they can be disturbed by air flow!! With six leads on a chip 1.6 x 2.7 mm you cannot do this job on a bad hair day........ I'm not sure I'll be able to mount these components if Parkinsons ever sets in!!

Cheers,

Hugh
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Old 16th June 2007, 06:33 AM   #102
Nordic is offline Nordic  South Africa
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Can we stick to the topic please? This is not a blog.
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Old 16th June 2007, 06:42 AM   #103
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Quote:
Originally posted by AKSA
P-A, I've started using surface mount; the DMMT5401 supermatched pair for the LTP. You must be very careful not to draw breath while mounting them - they are so light they can be disturbed by air flow!! With six leads on a chip 1.6 x 2.7 mm you cannot do this job on a bad hair day........ I'm not sure I'll be able to mount these components if Parkinsons ever sets in!!

Cheers,

Hugh
Wow Hugh Times they are changing Have you also started to make double sided boards? It's time you to upgrade your Nirvana kit to "Outer Space" kit.

If it is SOT363, they are not the easiest ones to solder by hand. EDIT: I see that they are SOT26, a bit bigger than SOT363.
Click the image to open in full size.
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Old 16th June 2007, 02:54 PM   #104
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Hugh,

Sorry but I couldn’t resist and of course you are right on with the comment.
I like class A amps for what they bring to the table but find them terribly inefficient, the AB’s I’ve made over the years (mostly Borbely designs) did not cut it, they were no AKSA of course which I haven’t had the pleasure to hear.

I do have some Zen and Aleph’s but drive them with vacuum line amps and in no way I’m married to Pass designs but like them for their simplicity and good sound. Time may come to try AKSA, been tempted for some time after hearing comments from many DIYaudio members.

BTW, my user name here is an acronym of my name Antonio Passalacqua with the added “gear” which many think it implies that I’m a Pass nut so to speak.

I appreciate your kind words, you are a real Gentleman
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Old 16th June 2007, 04:00 PM   #105
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Quote:
Originally posted by AKSA

On AKSAs,

This amp was deliberately designed to very slightly color the sound with typical levels of 0.04% H2 and H3. The principle was the known psychoacoustic masking of these harmonics on the higher order harmonics spuriously created in most SS, feedback amplifiers...

Cheers,

Hugh [/B]

Hello

Since the higher order harmonics are still there, how do H2 and H3 won't mix with them ?

Not that I doubt that it's working but I'm surprise of the principle.

Is there any good texts on the web about the psychoacoustic masking of H2 and H3 ?

Thank

Gaetan
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Old 17th June 2007, 07:49 AM   #106
AKSA is offline AKSA  Australia
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Gaetan,

E. Larsen and R.M. Aarts (2004), Audio Bandwidth extension. Application of Psychoacoustics, Signal Processing and Loudspeaker Design., J. Wiley.

E. Larsen and R.M. Aarts (2002), Reproducing low-pitched signals through small loudspeakers, J. Audio Eng. Soc., March, 50 (3), pp. 147-164.

Hugh
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Old 17th June 2007, 07:54 AM   #107
Hartono is offline Hartono  Indonesia
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"Is there any good texts on the web about the psychoacoustic masking of H2 and H3 ?"

In my observation , adding small level of low order harmonic, is like adding a little contrast on your TV.


Hartono
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Old 17th June 2007, 08:36 AM   #108
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Default Perfect Hartono!


You have the "vision"

regards,

Carlos
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Old 17th June 2007, 08:37 AM   #109
Hartono is offline Hartono  Indonesia
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thanks
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Old 17th June 2007, 08:57 AM   #110
AKN is offline AKN  Sweden
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Quote:
Originally posted by Hartono


In my observation , adding small level of low order harmonic, is like adding a little contrast on your TV.
Adding contrast (video) is like expand the dynamics (audio) in my vision.
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