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Old 5th December 2012, 07:14 PM   #711
smms73 is offline smms73  Portugal
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Yes George.
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Old 5th December 2012, 07:31 PM   #712
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Quote:
Originally Posted by smms73 View Post
last week i visited a audio show with a lot of high end products, and that make me want to build an amplifier without feedback, .
Did you visit Zen Audio room ?
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Old 5th December 2012, 07:37 PM   #713
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I think i did RCruz, why you ask ?
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Last edited by smms73; 5th December 2012 at 08:05 PM.
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Old 5th December 2012, 07:47 PM   #714
smms73 is offline smms73  Portugal
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Quote:
Originally Posted by Joachim Gerhard View Post
Big project, good luck and i look forward for your amp design.
I do not think that using feedback in the voltage amplifying stage is a problem but to make the output separate from the input feedback is certainly a good idea. I still have good memory when i first heard the Threshold Stasis, no sharpness and grain at all and a HUGE soundstage.
I have been away from audio from some years, and it seems that HD audio at 24bits is getting mature now. I have listening to some records at 24b/96K and i think it is a big step from cd 16bit quality. So i have to build an amplifier to get the best out of the increase resolution. I have some ecological concerns about pure class a amplifiers, i am thinking about using this very good idea from Matsushita

http://www.gtkc.net/files/class-a+.PDF

This was invented in the 70´s , nowadays we have much better components and i think it can be made a good amplifier based on this, i have already found some mosfet for the output. The output mosfets will have a current bias of 10 ampers and 1,8 volts each.

I also think that having feedback in the voltage stage is not a problem, but i will make the output current amplifier separate from the voltage amplifier , it will be like a giant buffer . So i can experiment with different designs in the voltage amplifier.
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Old 5th December 2012, 08:56 PM   #715
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Interesting concept, a kind of current dumper. I have a recent QUAD amp that works quite well. The only thing i do not like is that it has quite drastic bandwidth limiting over 20kHz.
I tried to open the case to do some modification but so far i could not get inside.
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Old 5th December 2012, 08:57 PM   #716
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Elite Series Quad
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Old 5th December 2012, 08:59 PM   #717
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Here is the review with some measurements :http://www.avrevolution.com.au/SiteM...ad_QSP_HFN.PDF
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Old 5th December 2012, 09:33 PM   #718
smms73 is offline smms73  Portugal
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Quote:
Originally Posted by Joachim Gerhard View Post
Interesting concept, a kind of current dumper. I have a recent QUAD amp that works quite well. The only thing i do not like is that it has quite drastic bandwidth limiting over 20kHz.
I tried to open the case to do some modification but so far i could not get inside.
No Joachim is not current dumper .
Is a amplifier in class A that has a floating power supply , and a amplifier in class AB that the only function is keep the midle of the power supply of class A amplifier equal to input signal, Both amplifiers have unitary voltage gain.
maybe this picture is more clear.
Attached Images
File Type: png class a+.png (15.7 KB, 225 views)
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Old 5th December 2012, 09:39 PM   #719
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this type of circuit permits that the output stage works on class a but with low dissipation as the voltage across the output mosfet or transistors are very low. Ofcourse one has to be carefull with the class ab stage also, i have made some simulations and it seems to work very good.
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Old 5th December 2012, 10:14 PM   #720
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OK, now i see it better. I expected the Class AB amp at the output but this is the other way around. Does that mean that the Class A amp modulates the artificial ground between
V1 and V2 ?
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