IXYS depletion MOSFETs: What are they good for? - Page 2 - diyAudio
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Old 28th October 2009, 02:56 AM   #11
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Let us know when you figure out the name... The use of a depletion mode FET simplifies the design and makes it more tube-like in concept, if not in sound. I prefer to view the Ixys depletion mode fets as pentodes without heaters and extra annoying pins. Treating them as such may prove to be interesting.
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Old 28th October 2009, 04:13 AM   #12
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I think Hiraga did one of those...

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Old 28th October 2009, 05:15 AM   #13
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I nosed around a bit in the forums devoted to Hiraga's works, and haven't seen mention of a transformer coupled amp yet (not that that means a whole lot). The concept is so obvious, I can't believe no one's done it before. The addition of a deplection mode output device adds a touch of innovation, but not a whole lot, Anyway, it's an excuse to dust off the pair of One Electron UBT-1s that have been gathering dust, because this application is made to order for them.
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Old 28th October 2009, 10:23 AM   #14
flg is offline flg  United States
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I suppose the lowish idle current you would want for the typical transformer might contradict the highish idle current you would want for the MOSFET to be in a linear area? Unless maybe a para-feed type topology were used
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Old 28th October 2009, 11:25 AM   #15
Ejam is offline Ejam  Australia
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Default Hiraga Amp

Hiraga's SE Mosfet amp (called the Nemisis) from memory used a Hitachi lateral mosfet (2SK135) and an output transformer (64 ohm primary winding). The mosfet had 1A of current running through it. So I think the UBT-1 would be well cooked, even fried. Also if you check Bonavolt's website you should find a circuit of the Nemisis there. Hope this helps.

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Old 28th October 2009, 11:34 AM   #16
Ejam is offline Ejam  Australia
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Default Wrong Spelling

Sorry, got the spelling wrong, it should be "Nemesis". Jan Didden at Linear Audio has a few words about rebuilding one of these amps. Try http://www.linearaudio.nl/nemesis-1.htm
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Old 28th October 2009, 12:22 PM   #17
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Quote:
Originally Posted by Ejam View Post
Sorry, got the spelling wrong, it should be "Nemesis". Jan Didden at Linear Audio has a few words about rebuilding one of these amps. Try http://www.linearaudio.nl/nemesis-1.htm
The original output transformer is no longer available, but I have a prototype from another manufacturer on order. As soon as I get it, I will test it in the original Nemesis and with one of these depletion mode MOSFETs. I'll keep you guys posted.

I am currently using the ECF10N16 from Exicon, but the new device should make the circuit even simpler. Maybe even beat Nelson at his own game

jd
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Old 28th October 2009, 12:42 PM   #18
Zen Mod is offline Zen Mod  Serbia
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janneman - have you any info about these xformers ?

winding ratio etc ?

edit : I forgot that in original schematic is written 64:8 ohms

any other info , besides that ?
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Old 28th October 2009, 01:03 PM   #19
Gordy is offline Gordy  United Kingdom
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Quote:
Originally Posted by Nelson Pass View Post
I think Hiraga did one of those...

This one perhaps...

" Schematic by Jean Hiraga published in "L'Audiophile" named Némésis. "

2SK135 SE Amp
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Old 28th October 2009, 01:24 PM   #20
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