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B1 Buffer Preamp
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Old 7th October 2012, 09:54 PM   #3581
Danger Mouse is offline Danger Mouse  Germany
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Quote:
Originally Posted by Salas View Post
Shoot them some clean macro pictures front & back, we will be able to advise if real Toshiba, and if they are valid save them for something else. For B1 get BL as Russellc wrote.

P.S. That's 11% error, don't trust the analyzer for any real IDSS matching in the future.
Realy able to advise if real Toshiba?

Do you can do this also for 2SJ109bl i have 4 dont know they are real ore not?
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Old 7th October 2012, 10:13 PM   #3582
Salas is offline Salas  Greece
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I have such to visually compare too. But better we take that to the sticky thread: http://www.diyaudio.com/forums/parts...l-copy-47.html
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Old 7th October 2012, 11:01 PM   #3583
Danger Mouse is offline Danger Mouse  Germany
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ok
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Old 7th October 2012, 11:30 PM   #3584
tessier is offline tessier  Canada
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Hi

Here is the photo of my 2SK170.

If it's not toshiba, could it be genuine 2SK170 from another maker ?

Thanx

Paul
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Last edited by tessier; 7th October 2012 at 11:34 PM.
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Old 8th October 2012, 01:53 AM   #3585
tessier is offline tessier  Canada
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Hi

I've just look in a box of old amps boards and I found six 2SK170 on one amp board.

I have done again the IDSS test, using a 9 volt battery, and it have a IDSS of arround 5.3 ma for all those six 2SK170

They have a bit low IDSS, but can I use those 2SK170 for the B1 ?

Thanx

Paul
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Old 8th October 2012, 05:34 AM   #3586
Salas is offline Salas  Greece
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B1 Buffer Preamp
Quote:
Originally Posted by tessier View Post
Hi

Here is the photo of my 2SK170.

If it's not toshiba, could it be genuine 2SK170 from another maker ?

Thanx

Paul
They look Toshiba.
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Old 8th October 2012, 05:43 AM   #3587
tessier is offline tessier  Canada
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Hi

And how about the six 2SK170 I found on one amp board, they have a IDSS of arround 5.3 ma, can they be ok for the B1 ?

Thanx

Paul
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Old 8th October 2012, 05:56 AM   #3588
Salas is offline Salas  Greece
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Quote:
Originally Posted by tessier View Post
Hi

I've just look in a box of old amps boards and I found six 2SK170 on one amp board.

I have done again the IDSS test, using a 9 volt battery, and it have a IDSS of arround 5.3 ma for all those six 2SK170

They have a bit low IDSS, but can I use those 2SK170 for the B1 ?

Thanx

Paul
If they are GR then that IDSS is in range. If they are marked BL then that IDSS tells they are wrong parts.
5.3mA is for Yfs ~30 which is not low in general although a 9mA BL gets you to ~40. That figure is the "amplifying might" of the part. In B1 all this is utilized as current drive, the more its got the less THD and output impedance it presents, but bit more input capacitance. And more IDSS that goes with the territory ups the TO-92 cased JFET's heat dissipation too. B1 was designed around BL grade, 8-9mA is a good compromise. V grade would need a cooling aid without giving analogous gain in might because the Yfs curve tappers off as it ascends its scale. All in all, its you compromise by a margin if going with GR but you still got a B1. Although on the somewhat weaker performance side.
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Old 8th October 2012, 06:00 AM   #3589
tessier is offline tessier  Canada
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Hi

I've look and those six 2SK170 are GR grade.

So with those jfet I would have much more thd in my B1 ?

Thanx

Paul

Last edited by tessier; 8th October 2012 at 06:03 AM.
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Old 8th October 2012, 06:05 AM   #3590
Salas is offline Salas  Greece
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Preferable than the 3mA ones.
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