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Old 23rd July 2003, 08:25 PM   #1
Fuling is offline Fuling  Sweden
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Default One (1!!) transistor clapping...

Ladies and gentlemen, I have dream...
A dream about a good sounding class A amp with about 5-6 W output power, full frequency range, fairly low distortion, descent input impedance and so on. Nothing special so far, right?

The thing is that I want to use one, no more, active device per channel. Power supply included (OK, except for the rectifier)
Did I mention that I want an efficiency of at least 35-40%??

In my dream I can visualize some items from my junkbox:
Some miscellanous power mosfets.
A box of mains toroids with a lot of different voltage/current ratings.
A pair of big EI chokes (DIY) that should function well as "Plate loads".
A pair of big heatsinks.

Iīm thinking something Zen-like here, and I need all you fanatics out there to think with me...
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Old 23rd July 2003, 08:35 PM   #2
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you sound like you're describing a Son of Zen amp.
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Old 23rd July 2003, 08:42 PM   #3
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- class A
- efficiency 35-40%??
- one active device



hmm. you want to use a big inductance instead of an ccs? i remember Nelson wrote something about that in the board some time ago. I have the problem how to set the bias in this circuit.
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Old 23rd July 2003, 08:46 PM   #4
Fuling is offline Fuling  Sweden
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Well, the SoZ has two active devices per channel.
I want one.
Why do I want one?
It would be...cool

I already own quite a few good power amps so itīs not that I need another one, Iīm just doing this for the challenge.
I think the main problem will be to apply feedback that doesnīt require a stabilized power supply.
Donīt even now if itīs possible, but hey, thatīs why I started this thread. If I already knew the answers Iīd wait and post the results once finished...
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Old 23rd July 2003, 08:48 PM   #5
Fuling is offline Fuling  Sweden
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till, yoy must have posted while I was writing
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Old 23rd July 2003, 08:50 PM   #6
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It MUST be possible, Nelson wrote it is. You need a coil of 1H or so. It must be a kind of circuit it old tube days when they had no ccs. I search but donīt find ....
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Old 23rd July 2003, 08:52 PM   #7
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Default ha!

http://www.diyaudio.com/forums/showt...8891#post78891
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Old 23rd July 2003, 08:54 PM   #8
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There was a design by Jean Hiraga, using a single power FET with in the drain lead a transformer from 64 Ohms to 8 Ohms. I'll see if I can dig it out.
Just last week I was offered a pair in Brussels. Damn!

Jan Didden
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Old 23rd July 2003, 08:55 PM   #9
Fuling is offline Fuling  Sweden
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I donīt think 1H is necessary. A while back I was messing around with a choke loaded source follower amp, those chokes where 100mH and they worked fine for an 8 ohm load.

I too have read something that Nelson has posted here about some choke loaded Zen, but I canīt seem to find it. Though, I remember he wrote something about feedback problems with unregulated DC, and looking at the (imagined) schematic, it seems logical.
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Old 23rd July 2003, 09:01 PM   #10
Fuling is offline Fuling  Sweden
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janneman, do you mean this one?

http://www.bonavolta.ch/hobby/en/audio/2sk135se.htm

Looks like something that I could rip...
Changing some voltages and currents and replacing the OPT with a choke and some output caps. Oh yeah, a coupling cap in the feedback loop, nothing fo the puritans
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