small signal device matching procedure (as in LSK170) - Page 3 - diyAudio
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Old 10th October 2008, 09:43 PM   #21
steenoe is offline steenoe  Denmark
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Default Re: Back at cha !

Quote:
Originally posted by FUCHSAUDIO

FET Matcher artwork is attached. www.expresspcb.com

Thanks.



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Old 30th October 2008, 03:43 PM   #22
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Default FETS Needed

I have neither the facility or skill to perform the parametric testing described in these threads but what little I understand makes good reading. I'm trying to reduce the DC offset in my Hafler 9180 which uses 2SK163 and 2SJ74 fets in the front end. If I can get a good set of matched pairs I believe I'll reduce my offset to under 5mv so I can directly power a low excursion midrange driver. Can anyone tell me where I may purchase a few pairs of graded - matched devices (or appropriate substitutes) ? Thanks
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Old 30th October 2008, 09:48 PM   #23
JimT is offline JimT  Canada
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Please recommend sockets for testing these. I have searched Mouser and Digikey and the shelves of the local Electronics store and only found sockets that require the legs to be bent to fit. I have a socket that sort of works for the LSK170's but am having no luck with a socket for the LSK389's.

Thanks
Jim
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Old 23rd November 2008, 07:48 PM   #24
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Default Sockets

I made my board using an 8 pin dip IC socket, and it works fine. If you use a quality socket (wil milled pins, not the bent/stamped ones) it works well. My design used both halves of the socket, in case the pins got lose on one side, you could use the other side. Since we used the test fixture in production, I wanted to make sure it lasted. The power and meter leads connect with alligator clips to 440 machine screws (1.5" long) as test posts. Came out nice....
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Old 13th May 2009, 04:33 PM   #25
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I also modified some IC sockets (the type with the gold
plate machined pins). Next plan is to build a multiple socket
tester to cover whole range of small sig Jfets to large mosfets
with TO-3 and also some type of socket for TO-220.
BTW, I have several of the Hitachi mosfets and know that
Hafler had some tester to match devices with. Does anybody
know what model that was and/or have schematic of Hafler's
tester?
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Old 13th May 2009, 08:56 PM   #26
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There WAS a Hafler device tester on EBay about 6 months ago!
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Old 14th May 2009, 08:37 AM   #27
h_a is offline h_a  Europe
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I think this topic is incomplete without some measurements

JFet matching and measured distortion - Part1

JFet matching and measured distortion - Part 2: LTP

Would be a pity if rare stuff like real measurements get lost in digital space.

Have fun, Hannes
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