One (1!!) transistor clapping...

Fuling · 23rd July 2003, 07:25 PM

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.

I´m thinking something Zen-like here, and I need all you fanatics out there to think with me...

HeadSh0T · 23rd July 2003, 07:35 PM

you sound like you're describing a Son of Zen amp.

till · 23rd July 2003, 07:42 PM

- 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.

Fuling · 23rd July 2003, 07:46 PM

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 it´s not that I need another one, I´m just doing this for the challenge.
I think the main problem will be to apply feedback that doesn´t require a stabilized power supply.
Don´t even now if it´s possible, but hey, that´s why I started this thread. If I already knew the answers I´d wait and post the results once finished...

Fuling · 23rd July 2003, 07:48 PM

till, yoy must have posted while I was writing

till · 23rd July 2003, 07:50 PM

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 don´t find ....

till · 23rd July 2003, 07:52 PM

http://www.diyaudio.com/forums/showt...8891#post78891

jan.didden · 23rd July 2003, 07:54 PM

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

Fuling · 23rd July 2003, 07:55 PM

I don´t 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 can´t 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.

Fuling · 23rd July 2003, 08:01 PM

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

23rd July 2003, 07:25 PM	#1
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	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. I´m thinking something Zen-like here, and I need all you fanatics out there to think with me...

23rd July 2003, 07:52 PM	#7
till Banned Join Date: Apr 2002 Location: Germany, Clausthal	ha! http://www.diyaudio.com/forums/showt...8891#post78891

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23rd July 2003, 07:35 PM	#2
HeadSh0T diyAudio Member Join Date: Sep 2002 Location: Toronto, Canada	you sound like you're describing a Son of Zen amp.

23rd July 2003, 07:42 PM	#3
till Banned Join Date: Apr 2002 Location: Germany, Clausthal	- 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.

23rd July 2003, 07:46 PM	#4
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	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 it´s not that I need another one, I´m just doing this for the challenge. I think the main problem will be to apply feedback that doesn´t require a stabilized power supply. Don´t even now if it´s possible, but hey, that´s why I started this thread. If I already knew the answers I´d wait and post the results once finished...

23rd July 2003, 07:48 PM	#5
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	till, yoy must have posted while I was writing

23rd July 2003, 07:50 PM	#6
till Banned Join Date: Apr 2002 Location: Germany, Clausthal	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 don´t find ....

23rd July 2003, 07:54 PM	#8
jan.didden diyAudio Member Join Date: May 2002 Location: Great City of Turnhout, Belgium Blog Entries: 6	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

23rd July 2003, 07:55 PM	#9
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	I don´t 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 can´t 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.

23rd July 2003, 08:01 PM	#10
Fuling diyAudio Member Join Date: Aug 2001 Location: Sweden (Mora)	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