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Old 14th August 2011, 07:35 AM   #31
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Quote:
Originally Posted by Nico Ras View Post
Here is a very simple amp schematic that has excellent performance that I published here some five years ago.

Nico
This circuit is close by those circuit, that was published in the german magazine "ELRAD" - go to post 13 about
Anybody have scan of AN-483B (Motorola)?
to download pdf file.
Also this thread could be of intetesrt in this case:
Edwin 20 watt (Elektor 1970 - May)
What means "I published here" ??
Here on diyaudio?
Or mean you an electronic magazine in your country?
Independent of this - can you give some advices about vintage and currently available electronic magazines from your country about
Overview from world's best historical and currently available electr/audio Magazines
Thank you very much therefore.
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Old 14th August 2011, 10:24 AM   #32
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Quote:
Originally Posted by Nico Ras View Post
Here is a very simple amp schematic that has excellent performance that I published here some five years ago.

Nico
What is the value of X1?
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Old 14th August 2011, 10:39 AM   #33
wahab is offline wahab  Algeria
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Originally Posted by ingenieus View Post
What is the value of X1?
Such that it makes with R49 a divisor with about a 2 ratio.
So R49 value is rather 220K , and same for X1.
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Old 14th August 2011, 10:55 AM   #34
tomat is offline tomat  Indonesia
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Originally Posted by wahab View Post
Such that it makes with R49 a divisor with about a 2 ratio.
So R49 value is rather 220K , and same for X1.

Wahaabb... my friend.. glad to see you agaiinn
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Old 14th August 2011, 10:58 AM   #35
wahab is offline wahab  Algeria
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Originally Posted by tomat View Post
Wahaabb... my friend.. glad to see you agaiinn
Hi , Tomat,
Good to see you by there.
Did your hybrid feedbackless amp finally become reasonnable ?..
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Old 14th August 2011, 11:07 AM   #36
tomat is offline tomat  Indonesia
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Originally Posted by wahab View Post
Hi , Tomat,
Good to see you by there.
Did your hybrid feedbackless amp finally become reasonnable ?..

yess.. i still enjoy it till now.. and that because your help too many thanks my friend
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Old 14th August 2011, 11:16 AM   #37
wahab is offline wahab  Algeria
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Originally Posted by tomat View Post
yess.. i still enjoy it till now.. and that because your help too many thanks my friend
That s great , running all that time means it is very reliable..

Last edited by wahab; 14th August 2011 at 11:19 AM.
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Old 14th August 2011, 02:33 PM   #38
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Quote:
Originally Posted by Nico Ras View Post
Here is a very simple amp schematic that has excellent performance that I published here some five years ago.

Nico
This is probably more in keeping with the title of this thread. Perhaps I should have titled it "Class B amp with low component count." Then again, the internals of the NE5534 and LM334 are not that simple and they have lots of components.
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Old 14th August 2011, 02:42 PM   #39
Bigun is offline Bigun  Canada
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Ingenious,

It's not clear that this offers lower parts count but thought you may like to read the article. Scroll down to the section with the title "Class B amplifier has automatic bias"

http://www.edn.com/contents/images/6702272.pdf
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Old 14th August 2011, 05:01 PM   #40
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Originally Posted by Bigun View Post
Ingenious,

It's not clear that this offers lower parts count but thought you may like to read the article. Scroll down to the section with the title "Class B amplifier has automatic bias"
Thanks. It look very interesting. The example given is for a headphone amp but the design should scale up well.

Automatic bias is something I have tried a few years ago. All I could prove then was that it is easy to fry transistors. This one makes me feel like getting back on that horse again.

I have had another look at the circuit in post one. It seems that the constant current delivered by the LM334 means that the resistors values for the Vbe multiplier can vary quite a lot while the circuit keeps working. There is an optimum setup that gives the lowest THD of course, but if one is willing to live with a compromise it should be possible to spec values that will work. This means that the dreaded pot is no longer needed.

Of course this has to be verified by building an actual version. For the price of a Big Mac in components(*) how can one resist?

You will also notice that I have tweaked the frequency response a bit, and made the symbols look a bit nicer.

(*) Excluding power supply, heat sink, PCB, cabinet e.a.
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