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Old 14th July 2012, 01:17 AM   #12461
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Folks might be interested in this -- I had some PCB's made to accomodate different JFETs. With a pair each of 2N5460/2N5457 I can get the THD+N% below 1% Idss of the pairs was around 7mA.
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Old 14th July 2012, 02:18 AM   #12462
6L6 is offline 6L6  United States
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That's awesome! Will you sell the PCB and parts kits?
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Old 14th July 2012, 02:47 AM   #12463
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Quote:
Originally Posted by jackinnj View Post
Folks might be interested in this -- I had some PCB's made to accomodate different JFETs. With a pair each of 2N5460/2N5457 I can get the THD+N% below 1% Idss of the pairs was around 7mA.
Shoulda said -- the TDH+N% is well below 0.01%

2SK170 in GR and BL are generally available which is better than the 2n5457 (suddenly in short supply) -- and it may make sense to use 3x matched 2n5460.
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Old 14th July 2012, 09:09 AM   #12464
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Hi,
I ordered 10 of 2n5460 and see how they sound,Found a test circuit for them.
Cheers,
NS
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File Type: gif 2N5460 TEST.circuit.gif (6.9 KB, 549 views)
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Old 14th July 2012, 01:52 PM   #12465
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2N5460 is DSG, (not that it should matter).

Below is Erno Borbely's "Simple JFET Tester" -- of course it's set up for N-Channel devices, but just change the polarities, and reverse the direction of the current sources (you can use JFETs for the current sources since the diodes are rather hard to get.)

Engaging the first position of the switch gives the pinch-off voltage Vp, read by the volt meter. Shorting the source to gate (ground) gives Idss. Thus you can calculate gm.
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File Type: gif JFET_Test.GIF (6.3 KB, 530 views)
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Old 15th July 2012, 12:57 AM   #12466
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Hi Jackinnj,
Thanks for the pinouts I'll be sure to check those parts when they get here ,I got that circuit from their site, pins are different !
Thanks for the schematic it looks like it's easier to use
NS
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Old 19th July 2012, 03:57 PM   #12467
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This is with some patience -- a matched pair of 2N5460 and 2N5457 -- the source resistor on the IRFP240 was reduced from 0.68 ohms to 0.40 by placing 1R in parallel. (Every time you change the source resistors, you have to rebias the amplifier). The output transistors in this case are badly matched.

The scale is dBV and the output @2.83V=1.0W=9.0dBV

Click the image to open in full size.
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Old 19th July 2012, 04:04 PM   #12468
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HiJack :-)

Do you still sell F4 kits ?

And what about BA-2 front end kits ?

There is allmost nothing listed on your Pass page anymore.

It could be because you dont have any kits anymore, or it could be a fault on the website.

Could you entlighten me ?


Best regards
Arthur.
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Old 19th July 2012, 04:55 PM   #12469
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Hi JackinNj,
Is that a software FET tester? what interface?
Where can I get one?
My fets are on the way,,,,
I have a bunch of 170's in the gr region and all about 10 sj 74 are BL,Ive been stacking the 170 to a close match,I read that the P really needs to be about a ma or two more than the n do you know ?
Thanks ,
Board or kit news from you?
Cheers,
NoSmoking

Click the image to open in full size.[/QUOTE]
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Old 19th July 2012, 05:06 PM   #12470
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Quote:
Originally Posted by ArthurDK View Post
Do you still sell F4 kits ?
And what about BA-2 front end kits ?
Nope and nope

But now you know that with a little effort you can substitute for the 2SJ74.
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