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Old 17th July 2005, 04:39 PM   #31
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Default Michael started with this schematic, and i was following very close, as he asked me

To help him with the listening tests, he wanted to have a second, a third and a fourth opinion.

I have in close contact with him, since the intention to design his own amplifier, the first one was made with 21 Volts Symetrical, using BD139 if i can remember.

Everything was developed, step by step.

He also decided to construct some JLH reference amplifier, and the selected to show some JLH quality, was DOZ, because simple, fast to construct, inexpensive, and showing the JLH main characteristics.

He used this one as a reference, together Yamaha and Harman Kardon.

Many circuits were made, including a class D he designed because i asked him...he turn very tired, working 4 ours each nigth, and heavy work all day long...i got up and he got up too

Those schematics, that i will have no intention to publish, because all them superated by Symassym4 and Evolution 1 (symasym 5) were use as references to decide for a new aproach...and he never decided nothing by himself, many people was consulted about that, Including the King of Australia and the Baron of Saint Ivy...both of them with Gold titanium Berilium Diamond ears...the baron waste 40 years of live inside Professional Studios, learning day by day, how incompetent can be manking, including inside BBC Broadcasting Radio Studios.

The guys did not copy anything boys...he is really gooooood!

regards,

Carlos
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Old 17th July 2005, 04:42 PM   #32
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Default Yeah!..nobody told he copy nothing, but the accident, the simple existence

Of alike schematics, having some similarities, already represents, by itself, a finger pointed.

So, i decided to be very, very clear.

here is some images...just a small part of the ones i have, of his steps of research... 3 monthes, 4 hours each nigth..the one loose weigth and had some disease because of the effort, and small time to sleep

regards,

Carlos
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Old 17th July 2005, 04:48 PM   #33
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Default Here some more images...last one.

Was terrible to me, this guy appeared from nowhere... saying that was a computer programmer and will design an amplifier...


- I said:

WHAT!!!?

- And i want your cooperation Dx.


Was hard to me, having age to be my son...knowing three times more than I could learn with my gray hairs...having studied in Japan and worked for Sony

What a hell this chucrute!..how deer him, not beeing and EE, came here and say that will do that difficult job?

He made...he really made, i am testimony...hard to me in the first days...recognize, that this boy...very young boy related my age...he is really GOOOOOOOOD!

regards,

Carlos
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Old 18th July 2005, 09:34 AM   #34
djk is offline djk
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Just build an MC250 without the input impedance buffer section (unless you need a 200K input impedance) , makes the AKSA look complex.

http://berners.ch/McIntosh/Downloads/MC250_ser.zip
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Old 18th July 2005, 10:58 AM   #35
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Default There are secret parts on AKSA 55 that do not appear in your schematic.

And i ensure you that those parts are the ones that aid the beautifull, unbeatable treble.

There are small parts underboard, and some special components, not only related the material used to produce the parts, but also the strange and tuned values.

The board design also produces some coupling, and i could see some sandwitched board, and 3 caps in the middle.... those caps are SMD and painted with the same board colour.... almost invisible...have to put strong ligth to see them.

Hugh, despite beeing my friend, do not agree that exist something inside the boards sandwiched...he always tell us that do not exist, only some illusion.

Also has a magnetic coupling between the output coil with the input..... always near the oscilation.....near the threshold.

The King of Australia produces a wonderfull circuit...i cannot leave my life without the brigth of AKSA.... the voice of GEM and the Bass of Symassym....but all them can reproduce, alone, by themselves, full range of optimum sound.

If i have to decide with one to buy...i will go to Aksa.....also because the one that is there to be sold...ahahaha...the others we have to construct.

Also, in my point of view, only Jens Rasmussen and Jan Dupont can beat the AKSA board in design, will loose the tricks that are over there..... but they have no interest in that subject...so, the Royal Majesty, Hugh, the first and the great, the King of Australia, will continue to sell dozen units each day.

More than King of Australia, he is the king of frite potatoes with sweet ketchup, as his circuit is simple, and beating a lot of complicated designs, in treble, dinamics, purity, noise and distortions.

More than thousand stereo units sold, no complain!

If you hear one Aksa, with the parts hugh will send to you, and try to beat it, as i tried to do and i failed, you will give a shot in others circuit that have some identities, similarities with Hugh design...as those details, all together, are making the difference.

I made it, and tested, and i called friends to judge, 2 meetings to judge, blind A to B comparison testings were made.

But success and money are things from Devil guys... when you have money, you have not time to have fun with it.

Now Hugh is rich, you have to wait 15 days to have your circuits mailed...as busy he is...having not time enougth to scratch his own backs.....so.... cannot spend the money that is entering...have not also time to make good acountings.... the money may be under the cushion...ahahahaha.

Kidding, as usual guys...

regards,

Carlos
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Old 18th July 2005, 09:08 PM   #36
MikeB is offline MikeB  Germany
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Hi !

Okay, time for some details about this amp:

I like this amp, it's "easy" to build, no complementary
transistor matching is necessary (except outputstage),
no exotic and hard to get vas-transistors, very
reliable, low DC-offset, excellent thermal stability...

My impressions about the sound:

Very clear, transparent, detailed and alive sound, and
frightening dynamics, the amp plays effortless at high
levels, having good control over the speakers resulting
in very tight deep bass.
Voices are reproduced like with a DoZ, simply stunning !
Guitars and pianos are a real pleasure...

My biggest surprise was the soundstage, that wide that
i checked speakerpolarity at first powerup, but when
listening to music, every instrument was pinpointlocatable.

And now, the numbers !

All values taken from sims...

Max swing at 4ohm: 32.6v (133watts)
Openloopgain: 1:32000 (gbw: 237mhz)
Closedloop: 1:45 (0.7v drives amp to max)
Feedbackratio: 57db
TIM: ~0.003% (4+7khz)
Slewrate: ~19v/us

Dampingfactor with outputcoil:
20khz into 8ohms: 120
1khz into 8ohms: 2400
100hz into 8ohms: 12000

Dampingfactor without outputcoil:
20khz into 8ohms: 6000
1khz into 8ohms: 12000

THD-values:

2.8v into 4ohms 20khz: 0.005%
2.8v into 8ohms 20khz: 0.004%

12v into 4ohms 20khz: 0.008%
12v into 8ohms 20khz: 0.007%

28v into 4ohms 20khz: 0.023%
28v into 8ohms 20khz: 0.016%

2.8v into 4ohms 1khz: 0.003%
2.8v into 8ohms 1khz: 0.002%

12v into 4ohms 1khz: 0.002%
12v into 8ohms 1khz: 0.002%

28v into 4ohms 1khz: 0.019%
28v into 8ohms 1khz: 0.007%

I personally believe that thd-levels below 0.003%
for a poweramp are nonsense, this represents the
resolution of a single bit from 16bit-CD.

I also attached "symasym5", using slightly different
feedbackcompensation. This versions gives a softer/sweeter
sound, sounding more precise, revealing even more details...
Carlos did not like it, too soft for his taste ?
THD numbers drop slightly for no5.
Soundstage becomes slightly less wide, but deeper.

And yes, i know that this topology is not new...
(But it's a damn good one !)

Michael
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Old 18th July 2005, 09:11 PM   #37
MikeB is offline MikeB  Germany
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Ah, i think Carlos forgot to show the upper side of the PCB...
(Of course, this heatsink is too small for longtime full power)
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Old 18th July 2005, 09:19 PM   #38
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Default I do not dislike it...but I prefer the Symassym4, with the standard RC from colector

to colector.... sounded best than the Miller cap 68 pf experience we made.

This one is good.... a softer amplifier, less agressive than Symassym 4, the one may broke Cristal glasses with its powerfull metalic treble.

regards,

Carlos
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Old 18th July 2005, 09:25 PM   #39
MikeB is offline MikeB  Germany
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"metallic trebles" ?
That's a very bad thing to tell about an amp...

Mike
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Old 18th July 2005, 09:32 PM   #40
AAK is offline AAK  United States
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Hi Mike,

What equipment did you use to calculate THD.

Thanks,

Al
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