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Replacement For Toshiba 2SK170/2SJ74
Replacement For Toshiba 2SK170/2SJ74
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Old 19th September 2019, 12:27 AM   #411
ticknpop is offline ticknpop  Canada
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Replacement For Toshiba 2SK170/2SJ74
A reasonable idss match is better than 10%, some like 5 % , or even tigher, but it changes with temperature, even holding them in your fingers changes the idss,
. You need to let them stabilize in your idss test for a couple of minutes, with no breeze, and donít touch them , even changes in house temperature causes some drift, so measure them at the same time of day

The idss value you need depends on the circuit design.
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Old 21st September 2019, 07:49 AM   #412
astromo is offline astromo  Australia
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Quote:
Originally Posted by Leicaphile27 View Post
I'd like to thank everyone for their helpful replies. Especially on how to measure IDSS. The Jfets I purchased from Spencer in Singapore haven't arrived yet. Measuring them should be straightforward. My question, however, is more along the lines of how much variance between the N and P channel is okay? Also, spec variance for BL grade range from 6-12...what it optimal and what happens the further you from optimal. Does it increase noise? Does sound quality deteriorate?
Refer here for the store's advice on JFET matching and the relevance of tolerance:

JFET matching information – diyAudio Store
Quote:
The JFET matching tolerance required for any of Nelson's projects is 1mA
You can fact check that detail through the various threads here and over at First Watt / PassDIY.

EDIT:
Fun fact / side-note - JFET guru, Erno Borbely, sold JFETs matched to 0.5 mA Idss according to the archived price list that I found:
https://web.archive.org/web/20100215.../Compprice.pdf

So, the noted comment from the store would not appear to be unreasonable.

Last edited by astromo; 21st September 2019 at 08:10 AM.
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Old 25th October 2019, 12:17 PM   #413
codyt is offline codyt  United States
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Anybody know if the eBay user punkydawgs (in Sacramento) is selling the real deal? Has several listings for 2SJ74 and 2SK170 right now.
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Old 25th October 2019, 12:19 PM   #414
ItsAllInMyHead is offline ItsAllInMyHead  United States
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Quote:
Originally Posted by codyt View Post
Anybody know if the eBay user punkydawgs (in Sacramento) is selling the real deal? Has several listings for 2SJ74 and 2SK170 right now.
Yes, he is a verified/reliable source.
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Old 25th October 2019, 12:29 PM   #415
Boydk is offline Boydk  Denmark
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Same impression here. Everything Iīve bought from him was genuine
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Old 25th October 2019, 02:35 PM   #416
codyt is offline codyt  United States
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Perfect - thanks!
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Old 25th October 2019, 10:28 PM   #417
Extreme_Boky is offline Extreme_Boky
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Join Date: Dec 2003
Toshiba 2SJ74 + 2SK170 MATCHED PAIR 0.03mA AND 4mV (10ma Idss Range)
AU $51.29
Postage:US $18.22 (approx. AU $26.70)
Total: AU$80
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Old 25th October 2019, 10:40 PM   #418
Dennis Hui is online now Dennis Hui  Canada
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Replacement For Toshiba 2SK170/2SJ74
Quote:
Originally Posted by codyt View Post
Anybody know if the eBay user punkydawgs (in Sacramento) is selling the real deal? Has several listings for 2SJ74 and 2SK170 right now.
Mr. Pass has written about punkydawgs in post #20:

Replacement For Toshiba 2SK170/2SJ74
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Old 25th October 2019, 10:53 PM   #419
6L6 is offline 6L6  United States
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Replacement For Toshiba 2SK170/2SJ74
Still cheap compared to rare tubes -


TubeDepot.com | Telefunken ECC83 / 12AX7 Ribbed Plate
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Old 25th October 2019, 10:57 PM   #420
Mark Johnson is offline Mark Johnson  United States
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Replacement For Toshiba 2SK170/2SJ74
At least one First Watt design has been re-engineered to use other, current production, non Toshiba semiconductors. If you don't want to spend AUD 80 for Toshibas, either perform some re-engineering yourself, or buy the amp in the diyA Store that's already been re-engineered. Or I suppose you could simply accept the fact that some obsolete semiconductors sell for the same prices as obsolete vacuum tubes. Que sera, sera.
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