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Old 20th February 2010, 05:12 PM   #461
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J2 is 30 WPC into 8 ohm and 15 WPC into 4ohm.
This suggest that the bias current is about 1.4A.
Maximum output voltage needs to be at least 21.9v, so rail voltage should be higher, maybe around 23-24 volt considering the 18V transformer.
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Old 20th February 2010, 07:28 PM   #462
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hi guys,
need opinion,
recently i used Class A 1! mosfet solid state mono block 5watt build from www.audioprjects.com /Mark housten created. it was modified from zen class A Nelson Pass. the sound is so sweet, but difficuilt to drive my 2 way dayton bookshelf.
My qoustion is:
is there better modified to push-pull, or put another N-mosfet like zenNnelson pass ?
my travo(5A) secondary: 12 volt, third : 6 volt. can i medified s2'nd & 3'rd to make hybrid to drive 2c51 tube for being buffer ? what kind a schema should i build ?
welcome any suggestion !
thank's anyway !
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Old 20th February 2010, 08:02 PM   #463
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Hi spiritm2r,

ZCA from Mark Houston is very good with fullrange (high sensitivity) speakers. I use them with my Audio Nirvana super10 in downsized Autograph replica, without any correcting circuit, and the sound is delicious, with ample, tuneful bas . You should try it with FRs, or try Pass' "DeLite" amp.

Good luck,
M.
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Old 20th February 2010, 10:25 PM   #464
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Not forgetting about the Source resistor question but, does this post raise some questions? Answer some???
Aleph Current Source Mod
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Old 20th February 2010, 11:59 PM   #465
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Quote:
Originally Posted by flg View Post
Not forgetting about the Source resistor question but, does this post raise some questions? Answer some???
Aleph Current Source Mod
just another way to skin a cat .......

I'm not saying that any other is better - but - you must count that that way you have max 2V window for Uce of small bjt .

is it enough - try ;

for moderate and medium levels certainly is , but trouble is around extremes .
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Old 21st February 2010, 03:00 AM   #466
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Breaking my new toy!
Have you tried it Zen Mod?
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Old 21st February 2010, 04:59 AM   #467
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O.K. this what I got so far...




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Old 21st February 2010, 08:59 AM   #468
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Quote:
you must count that that way you have max 2V window for Uce of small bjt
I do not understand why.
Or do you mean when using power Jfets only?
My intention is to mod an Aleph J, using regular Fets.

Last edited by bobodioulasso; 21st February 2010 at 09:24 AM.
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Old 22nd February 2010, 11:33 AM   #469
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Yes, in an Aleph CS, the "govonor" transistor would have much less Vce due to the lower Vth of the Sic devices. The operation of this area of the circuit will degrade because of this. In a J2 however...
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Old 22nd February 2010, 12:32 PM   #470
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Looking at the simplified schematic of the J2 I wondered if the LU1014D might be used to build a 5W version. I stole the schematic from Nelson and wrote in some values. Note I added a big 4ohm source resistor for the bottom LU1014 it was either that or run the front end at a higher voltage. Even at this 5W level keeping that tiny LU1014 will take some work! Keep in mind this is still just a simplified schematic.
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