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Old 15th May 2006, 07:09 PM   #1
masag is offline masag  Germany
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Default Japanese amp design

Dear members of this forum,

this is my first thread.

I found in the web some interesting japanese amp-designs.
http://www.geocities.jp/mutsu562000/

One of them seems to me very attractive because it is well dokumentated too.

Could somebody take a look at it and give me some advice about expected power, oe even it is easy or difficult to build?
http://www.geocities.jp/mutsu562000/...m/e/hp037e.htm

I have attached the schematic of the amp

Thank you very much

Sam
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Old 15th May 2006, 07:20 PM   #2
MikeB is offline MikeB  Germany
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I am sorry, 5.5% THD at 1watt ? There are even simpler amps performing better not using feedback...
This is not an amp, it's a harmonizer / musical instrument.

Mike
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Old 15th May 2006, 07:36 PM   #3
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Interesting, a negative output resistance Class A amp.
Forr on this forum has being experimenting with this feedback arrangement.
If you are a beginner I would not recommend this design, something a bit more conventional to start with e.g Gainclone
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Old 15th May 2006, 07:49 PM   #4
MikeB is offline MikeB  Germany
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The author writes that negative outputimpedance is not possible with this circuit.

Mike
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Old 15th May 2006, 09:43 PM   #5
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Probably this positive current feedback network just lowers output impedance but still keeps it positive, with higher open loop gain it would be possible to go negative. 330mA for +-27V rails in class A single ended makes completely no sense and nearly zero efficiecy. I would go for something like +-10V and 1A to possibly call it 'power' amplifier.
Masag, leave it. It is nonsense and a lesson taken from it should be 'never trust transistor beta'.

cheers
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Old 15th May 2006, 10:03 PM   #6
masag is offline masag  Germany
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Thank you very much, for your fast replay!

Maybe I should try your amp Mike?

What's about that design? I t is on the same website?
http://www.geocities.jp/mutsu562000/...m/e/hp179e.htm
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Old 16th May 2006, 03:54 AM   #7
EUVL is offline EUVL  Europe
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This last one is the Kaneda Full Symmetry design, which was first published some 20 years ago. There have been many many different versions built, including Power JFETs, all MOSFETs, UHC-MOSFETs, .... both in Class A ans Class AB. You can even buy a book from Kaneda on Amazon.co.jp that gives full instructions how to build one (in Japanese). No PCBs, all point-to-point wiring. Beautiful craftmanship.

The ISBN number of the book is 4-416-10405-7 @ 3200 Yen.

Amongst others, you need to match all transistors; and you need to know how the circuit works. I am sure there are enough experienced builder here who can give it a go.


Patrick
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Old 16th May 2006, 07:48 AM   #8
MikeB is offline MikeB  Germany
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masag, your last shown looks quite good, if i am right you will need lateral mosfets to have it thermal stable.
If you try mine you have the advantage that you can order all parts necessary at once at www.reichelt.de except the mpsa18 and outputdevices maybe.

Mike
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Old 16th May 2006, 07:54 AM   #9
EUVL is offline EUVL  Europe
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> if i am right you will need lateral mosfets to have it thermal stable.

Not necessarily.

As I mentioned, there are all sorts of versions being built in Japan with different output device types, including bipolar.

In addition, the 150R resistor shown at the drain of the second diff pair is a temperature dependent device (if I am not wrong NTC) to be mounted close to the Power FETs for temperature compensation.

And in my own experience, Toshiba 2SK1529, e.g., has negative temperature coefficient at bias < 1.3A (Vds up to 25V), and would be fine in that circuit with minor modifications.


Patrick
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Old 16th May 2006, 08:58 AM   #10
EUVL is offline EUVL  Europe
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Attached front covers of the latest books by Kaneda.
Book 1 is phono & preamp
Book 2 is power amp

Patrick
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File Type: jpg kaneda book 1.jpg (54.4 KB, 1725 views)
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