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Old 1st October 2008, 02:11 PM   #141
juma is offline juma  Serbia
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Default Re: AlephX with J fet driver

Quote:
Originally posted by gaborbela
Hi
I have these AlephX using the Kristijan PC boards .
Can I drive the AX with J fet .If yes can someone hepl me what do I have to change in the schematic so it make it better .
I attache the original schematic what these desing uses .
I have J fet 2SJ74BL/2SK170BL at least 50 pairs .Or if better to use 2SJ109BL/2SK264BL I can purchase that .
Can some one please help me please if is possibile to replace the Hexfet drivers wit J fet .
Thank for any help !!
Greetings

You will find answers to all your questions if you read this whole thread carefully from the beginning.
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Old 1st October 2008, 02:27 PM   #142
Zen Mod is offline Zen Mod  Serbia
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Default Re: AlephX with J fet driver

Quote:
Originally posted by gaborbela
Hi
I have these AlephX using the Kristijan PC boards .

why don't you ask KK ?



http://www.diyaudio.com/forums/showt...40#post1620540
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Old 1st October 2008, 07:49 PM   #143
gl is offline gl  United States
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I can think of three or four people who have built and posted Aleph-X amps with JFET front end circuits. You need to search for them. They're easy to find. Here is one that I have built and posted:

http://www.diyaudio.com/forums/showt...22#post1468122

I would be cautious regarding the KK schematic you posted. First, there has never been any evidence that he has built any of the circuits shown on his web site.

Second, I have built my own version of the Aleph-X and experimented with the basic circuit quite a lot. I don't like a number of KK's component values. His circuit will make sound, but it IMO it won't sound optimal. That being said, the good news is that all of the information you need to optimize the Aleph-X circuit is here on this web site.

Cheers,
Graeme
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Old 2nd October 2008, 12:34 AM   #144
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HI

The truth is I made a listening test in one side and it sound really great .I'm satisfied with the sound what I heard .
I read some post at the forum from those who made the change to use J-fet . Somebody wrote is not to much improvement after the change , so I decided to stick with the original design .
Thanks to all for the help .
Greetings .
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Old 2nd October 2008, 03:29 PM   #145
gl is offline gl  United States
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I believe that the amplifier sounds better with JFET inputs and I've stated this in a couple of places. Macka has also said the same. And here is a related post by Nelson on the topic.

http://www.diyaudio.com/forums/showt...05#post1404305

It is worth the work to make the modification if you have the transistors. Unfortunately many don't.

Cheers,
Graeme
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Old 3rd October 2008, 04:27 PM   #146
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Yes,

I can only confirm that! The mod is so simple to perform (after most problems are solved now) that I would certainly try it.

William
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Old 4th October 2008, 12:19 AM   #147
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Hello

I read a lot of info about the J-fet drive AX and all I understand those people who did the modification still suffer with the offset problem .
I will wait until someone confirm that now his amplifier with the modification works well .
I do not want to wait 2 hours until the offset disappear or play with the expensive Scan speak drivers (I do not want to burn my speakers )
It happend me oneness that is enough to me .
I'm not against the modification, yes I would like to do that especially if is a sonically improvement . I just don't have the skills to do it by my own . If there is a schematic and works perfect I can do it but I'm not amp designer .

Greetings
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Old 4th October 2008, 08:59 AM   #148
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Hi,

what offset problem? It is the same behaviour of the absolute offset that you get when using a normal frontend. The speaker won´t see this offset as it appears at both outputs simultaniously. My relative offset is a few millivolts (<10mV) from startup till warm.

William
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Old 16th October 2008, 09:56 PM   #149
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Hello
OK that is a good news . Maybe I should try in my AX to .
I will carefully study the two schematics , I'll will see what are the differences between them .
After I will decide .
KK will not help , he design the AX after the basic schematic .I have to go on and study your verision how I can use it in my case .
Thank for all the information .
Greetings
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Old 16th October 2008, 10:16 PM   #150
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Hello
I have one question before I do anything to my Aleph X I want to understand all the parts in the schematic posted at 123.post .
The C7 & C8 that is a 4.7uF polypropylene capacitor ?
Please let me know if I understood well .
Thanks
Greetings
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