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Old 17th July 2005, 01:37 PM   #26
GEirin is offline GEirin  Argentina
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Hello

Destroyer X

Why " symassyn circuit is very modern and strange....?

Guillermo
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Old 17th July 2005, 01:58 PM   #27
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Default Made now a days and different in design

Not very standard for my eyes, a little bit crowdy, as AKSA produce quality using 7 transistors only, bootstraped, old and not strange it is.

Saludos hermano

Carlos
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Old 17th July 2005, 01:59 PM   #28
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the Dynaco 400:
http://home.indy.net/~gregdunn/dynac...400/index.html
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Old 17th July 2005, 02:07 PM   #29
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Default This one is strange too, sometimes the way people make the schematic

Some non standard way to draw differential and others usual circuits, produces the appearance that is a different amplifier, when studied with more attention, we can see the same traditional couplings, designed in other spatial position.

Thank you, this Dynaco is very interesting.

I will print it all, to have fun trying to understand it.

Thank you EVL or EDL, the guys from Paty, that made the kindness to post the link.

Will print now...thank you.

regards,

Carlos
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Old 17th July 2005, 02:26 PM   #30
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Default Oh! Epupa, i forgot to comment your information, that the design was founded in the..

Design of the seventies.

This produces to me, the confirmation of some suspections i already had.

That no one can produce something really new, because we are very poluted by the diagrams we use to see, and ideas we use to read and listen.... so, alike some noise in comunication, the noise in amplifier design may be this one... the memory of others for instance.

Or that everything you can imagine, someone probably, had the same idea, before you, or at the same time...we are no more isolated one each other....communications make things obbey some universal rules; connected to majority, price, reliability and quality.

Why i confirm to myself, my old suspections:

- I was with Michael, discussing by mail, daily and many times a day, related the best thopologie, my suggestion is that he could start from a Bootstrapped, and them simulate, construct and go researching to make it better than everyone.

- He decided to make his own design, starting from zero, by himself, since the first resistor, and to simulate each stage, watching distortions and wave forms in the Scope.

- Circuits gonne changing and changing, i have more than 15 circuits tested here, produced by him, they were constructed, simulated and compared...one, the evolution of the latter one, till he stopped satisfied with this, as he told me, could beat JLH, the Yamaha he has, a very expensive unit, and one Harman Kardon...he was satisfied, as the bass turns better than the Yamaha, voice and trebles was better than the 2 other ones.

And i could listen, and some friends also...the comparison was recorded... same speaker, same music, same level, 2 amplifiers beeing switched A to B, and recording going on.

This is some evidence that someone can start from nothing (only basic informs and design know how) and design something already done.

This is a little bit obvious, because if you use 35 volts, and decide by a 2 miliamps in the differential stage, you will have same resistor as hundreds of amplifiers, and almost all them use differential amplifiers....so, cannot scape too much of the "samething"

I ensure you all, the guy did not copy (with the purpose) nothing!...maybe, the good polution (old experiences, old memories, circuits he could see after, design books) he received year by year, could result in something already known.

This thopologie, the way was designed (sorry my ignorance) is the first one i could see.

Well, all life seaching amplifiers constructing, 46 years completed assembling amplifiers, more than 3.7K units constructed.... even beeing idiot, i have some experience about the subject, at least i watched many schematics.

In my computer, for instance, 3612 schematics are saved... and they are in 47 groups of different designs, different thopologies... but i have not all world schematics...this Dynaco i had not, for example.

And i was asking him (Michael) to copy, to start from something already considered good, not to loose time climbing stairs already climbed, not to re-discover the powder without smoke...but he finally insist to do everything by himself...since the first step.

But you have the rigth to observe similarities, also Hugh Dean, from Aksa, told us that he could see someone alike, made by Sanyo in the seventies, so...you may be rigth to observe that and to find some schematics that look alike.

I ensure you, this schematic, published, was designed by Michael

regards,

Carlos
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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
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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
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Hi Mike,

What equipment did you use to calculate THD.

Thanks,

Al
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Old 18th July 2005, 09:58 PM   #41
MikeB is offline MikeB  Germany
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Hi AAK,
I used the FFT-option in PSpice.

Mike
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Old 19th July 2005, 03:42 AM   #42
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Hello Mike,

Congratulations on your excellent design.......

happy amping,
K a n w a r
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Old 19th July 2005, 10:41 AM   #43
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Default Mike, Ich sprache nichst Englander..I do not speak english...so, have to make some

adaptations of my words.

Metalic when metal instruments are played...hitting metal, sound is metalic...grumpf!....grrrrr.

Or, explaining better; Metalic spoken as the quality, founded in some good amplifiers, that make them reproduce metalic sounds correctly, with all their harmonics, this reproduction makes them reproduce as bell as a real bell playing, not a bell sounding alike a plate beeing hitted.

hummm...think about that Miky...have to make some interpretation...some decodification... a gift for ya!

Uncle Charlie.
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Old 19th July 2005, 10:47 AM   #44
MikeB is offline MikeB  Germany
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Bratwurst !

Okay, got your point !

Mike
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Old 19th July 2005, 10:52 AM   #45
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Default Not only a a bratwurst... this is a roastbratwurst...visit Germany...a very...

nice place to visit or to stay.... land of Milk and honey. ahahaha!

Roast means toasted...people use to eat that with Rice, and some of them use to drink wine also.

regards,

Carlos
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Old 19th July 2005, 11:06 AM   #46
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Hi Mike,

Good design, very like the 1972 Hitachi AN double diff amp.

Point of difference is the cascoded drone side of the second diff pair; the Vbe multiplier, and the charge suckout on the output stage.

I'm a little concerned that you have only between four and five mA on the VAS stage, which is only 2.5mA at most driving the double emitter follower. Is this enough? You have measured 133 watts from the amp and strong imaging performance, which means phase shift is minimal, but is this drive current sufficient for current hungry loads?

Aside from that, and your conventional use of CCS and mirrors, it's a competent, well refined circuit and I give you credit. BUT, it's pretty standard fare, which in view of your earlier emitter drive for the VAS really surprised me!

Cheers,

Hugh
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Old 19th July 2005, 11:39 AM   #47
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Hi Hugh !

Thanks for the compliments,
I use this standard ccs to be independent from supplyvoltage,
and practical testings showed me that this 2bjt-ccs is the most
stable for PSRR.

I was also surprised that a low current vas is able to drive a
doubledarlington, even with these rloads and 660pf to gnd.
I have big 4ohm vented speakers, beeing quite hungry and the
syamasym plays effortless at high levels with these speakers.
It's correct that the idlebias of the vas is 2.8ma, but because of
the symetric nature of the vas this current goes up to 5.6ma
when swinging. Because of some interesting ft-effects in 2nd
diffamp this current peaks to 15ma when reaching slewratelimit.
So i have the advantage of using fast and linear smallsignal-bjts
for the VAS.

Yes, the amp is pretty standard topology, but outperformed my
other constructions, looks like old prooven concepts work best ?
The really difficult part was getting this gainmonster stable without
any overshooting or ringing...
Finetuning the feedbackcompensation seems to be the key to
good sounding amp.
The audible difference between symasym4 and 5 is not subtile,
but both are stable.

The phasehift of this amp is not very low, but very constant,
enforced by the "big" caps to gnd in the vas.
This seems to hide dynamic phasehifts, which might be the reason
for some amps to have poor soundstage ?

Mike
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Old 19th July 2005, 12:39 PM   #48
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Thank you Michael,

I will think hard on your comments. You have mixed in a lot of careful calculation and measurement; again, I give you full credit.

I agree that capacitor choice and dimensioning have the most profound effects in audio amplifier design. Of course, there are minor differences in designer style, but I recognise this as an excellent amplifier. You might now like to try voicing it for something really musical - an art, rather than a science - this is a wonderful approach that Carlos will help you with as well!

Thank you for sharing,

Hugh
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Old 19th July 2005, 02:48 PM   #49
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HI Mikeb! I didn't see you for a long time . ! Are you a programmer ?
Which way did you calculated TIM by?
Your schematic used 1 current mirror in VAS . Is it easy to build it ? Did you match these transistor ?

Thanks !
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Old 19th July 2005, 03:51 PM   #50
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Hi thanh !

Yes, we have met long time ago...
Yes, i am a programmer, the last days i hate it...

My TIM calculation is not very precise, that's why i've put a "~".
I mixed a 4khz and a 7khz signal (50:50), both having 6v swing
at output. In fft i've checked the frequencies, the peaks at 3khz
and 11khz are the IMD, all other freqs were much lower.
the 2 peaks were 150uv. 150uv/6v -> 0.0025%.
This is for sure not an accurate method...

This amp is easy to build, the transistors are matched by pairs,
the 2 mpsa18, the 2 2n5401 in 2nd diffamp, and the 2 2n5551
in currentmirror. Matching between 2n5401 and 2n5551 is not
necessary. Layout is critical because of the high gain, inputdiffamp
must use exactly the same gnd-level for input and feedback,
or will get massive hum.
For first powering up, i set the pot for bias to middle, and then
adjust the quiscent current to 50ma.

Mike
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