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Old 6th April 2006, 03:01 AM   #1
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Question JFET in-circuit matching

take a look at http://perso.wanadoo.fr/jm.plantefeve/sche.html "Zenquito" schematic,assume that the 2 JFETs are adjusted to matched Idss,would the AC characteristic of the circuit be influenced by the different value of the presets???
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Old 7th April 2006, 01:52 AM   #2
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Anyone???
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Old 7th April 2006, 02:55 AM   #3
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Default Zenquito

HI
I dont know how to matche or adjust those jets . I'm in the proces to build that amp , I would be intrested to if some one know about it .
I have the stuffed pc boards ,matched power mosfets but I didn't matche the 2sj103 / 2sk246 .
I even ask Mark J about it but unfortunatly he never answerd about it .
Some people from France who built the amp they say there is not to important to be matche .
In case if you have some information please let me know .
I'm more worried about the power supply because I'm going to use 2 pice of transformer .Each 2x40v 625VA. I'm paling to connect the transformer to give 20v instead 40 .
I dont know how will work ....
Any opinion.
I want to bias in to Class A ...
Thanks
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Old 8th April 2006, 10:41 PM   #4
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Could be
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Old 9th April 2006, 09:45 AM   #5
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Default Re: Zenquito

Quote:
Originally posted by gaborbela
HI
I dont know how to matche or adjust those jets ...
I have the stuffed pc boards ,matched power mosfets but I didn't matche the 2sj103 / 2sk246 .
Bonjour Jeno,

You can match 246 / 103 with this circuit. R is 390R for "Y" suffix, 820R for "GR" and 1500R for "BL". Match is for Id around 1.2mA.

On the PCB, trimmer will be 470R for "Y", 1kR for "GR" or 2.2kR for "BL".

Jean-Marc.
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File Type: gif match-fet.gif (1.9 KB, 333 views)
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Old 9th April 2006, 01:44 PM   #6
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HI
Thank you Jean-Mark .
At first I only found the BL type jets .
But a couple weeks after I found the Y type at far East . They had a matched par power mosfet so I orderd from there .
I still not finnished the amplifier but I'm very close to it .
I will let you know when I'm done with . Just one question , when I use these shematics for matching I have to much both jet the same time ? I have avaleble 12V DC so I will increase the value of the resistors ?
Thanks one more time ...
Regards
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