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Old 23rd March 2005, 10:24 PM   #51
jmateus is offline jmateus  United States
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Default Same topic

Yes, wright, when?
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Old 23rd March 2005, 11:03 PM   #52
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When we have the last version heheh... Who make in the eagle?
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Old 24th March 2005, 04:56 AM   #53
X.G. is offline X.G.  China
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HI,the sch which destroyer X posted is almost same as a Chinese DIY's circuit in 1983 which is source from the "super A bias circuit" of japanese JVC,and I heard that JVC had even made a IC of "super A bias circuit"

the "super A bias circuit" can follow the working of the power stages.because of the 3 EF stages for power output,the key of the "super A bias circuit' now is that its V/I part have 3 Vbe ....sorry my poor english,I can't say more and clearer.

...if you have the JVC origional article(I don't have and don't know the name of it ,but the Chinese DIY's article maybe show all detail) ,you can know much about it.

cheers,
X.G.
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Old 24th March 2005, 09:12 AM   #54
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Default Yes X.G., we already discovered that was a JVC clone.

I was deceptive when i discover that all control was not made with a chip, and beeing out of the signal patch, as controls or commands, i appreciate complications, as they cannot destruct audio quality.

I imagine that an audio chip can control better and more functions, having more sensors of over current and things alike.

When they start to sell here..... i think was 1975 because of the car model i had those times, a Brazilian made German Passat 74 model... and people was saying that some chip was controlling whole thing...what a surprise when i saw three transistors in series, making the work analogue of one single resistor, having some better quality because can change resistance value to change bias...i was deceptive...but not entirely, as simple solutions are appreciate by me too....but, in reality, i was expecting something more sophisticated.

More recently, some year ago, people started to call Gradiente, as Gradwood..... if i can understand, this means Gradiente plus Kenwood...some joke we use to make here.... some Gradiente brand, and when you go to deep research, you find Kenwood signs painted over the board.... i am not sure if i am rigth about that conclusion, but, if Kenwood inside, and class A, switching to AB, i imagine that we can find the chip there.

Big efforts you make to write in English man...congratulations, not many Chinese have this courage...and made a clear communication....my Brazilian welcome to you, as my people, having some exceptions of course, but normally, my people like strangers...we have a lot of chinese here...they do not talk a word...they smile and laugh...and people runned to try to understand and help them....many have shops, and documents where obtained resulted of brazilian people that cooperate with them, going together to the public bureaucratic Departments to obtain the needed papers.

regards,

Carlos
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Old 24th March 2005, 10:11 AM   #55
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Gradiente sounds much better !

The Japanese are not very good in thinking up catching brand names, apparantly only find it important with luxury car brands.
(and still dont get it right)

I am often surprised by the quality of parts and extraordinary circuits in very old equipment.
Even today the components used in the Gradiente amplifier section is SOTA, some havent been produced for years.
I started using the 1095/2565 in the mid 80s, when they became available on the diy market, a few years later production stopped.
Up till today i have not seen output devices with higher performance figures.
To think that those devices were already used in late 70s japanese amplifiers.

Anyway, i find the floating bias thing on the Gradiente intrigueing.
I like to see if it works.
So count me in, i'll build the Gradiente too.
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Old 24th March 2005, 11:18 AM   #56
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btw:
personally i like to regular bias this at 5-10 watts/8 ohm, after that the floating bias jumps in.
I never felt for Japanese Super A things very much, with a proper regular class A level though this might become a high power semi-class A amplifier.
Suppose you have an amplifier that does 100 watts in full class A, with sliding bias up to +200.
Maybe something for the Super Leach?
Like the soft clipping transistors added, think i would like to try the amplifier without them first though.

Already reserved some components.
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Old 24th March 2005, 11:27 AM   #57
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Default You will not waste your time Jacco, the unit has as nice sound.

How i can describe it.

Sound is a little bit warm....has not scandalous brightness, not so clear fingers scratching an acoustic guitar... it is not sibilante, do not show too much air in the top highs, and do not distort hi frequencies turning it alike some noise of sanding some acoustic material.

The bass is Strong, have a fast punch and a nice decay, dinamics is interesting, not incredible, the Brazilian model had week supply, it works hot as a hell, can keep coffee in perfect temperature...just put the cup over it, with a small dish please.

CLASS, is the word, it has class in its sound, you can hear Frank Sinatra, singing New York in high volumes, the orchestra will be present, his voice will be strong, you will be moved by that sound...but will not make any scandle.... you will have not neighboors trying to kill you, as it distorts softly, can bother, but not too much.

Has an English man class.

When you put volume up, you have some idea that some Englishman is saying to you:

I beg you Pardon Sir, but some reduce of level can be adequate sir.

regards,

Carlos
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Old 24th March 2005, 11:52 AM   #58
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I have seen that kind of heatsinks before, thermal R is rather low.
I can imagine that it runs very hot.

An amplifier like this one deserves something bigger, i am thinking in the order of 0,50
At 10watts/8 in class A with 25vac toroids it would come down to a little over 55 watts dissipation.
That would keep a 0.50 heatsink at reasonable temperature with enough reserve for the added heat from the floating bias.

I have 20.000 square feet of garden around my home :
PUMP UP the volume !
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Old 24th March 2005, 12:05 PM   #59
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Default No No No!.... you born as a mistake man, better to have born as a prairie animal, to

Have more fun with that enormous garden to make holes and eat things there....as a human... with so big land.... may turn you too much lonely.

hehe.

Carlos
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Old 24th March 2005, 12:10 PM   #60
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Default Jacco, find the Leach amplifier constructed by Jens Rasmussen

It has 2 enormous heat sinks....each one at one of the amplifier sides...i think only one of them will be enougth to you, if external mounted....if internal...put some fan to help you.

Jens construct pretty amplifiers, also his partner, Jan Dupont, is very good in this field.

regards,

Carlos
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