2x 2Sk170 in place of 2SK389 and 2x 2SJ74 in place of 2SJ109?

jarthel · 16th July 2007, 03:12 PM

I've seen a reply where someone said it's okay to replace a 2SK107 with 2SK389 (same for 2x 2SJ74 in place of 2SJ109) but I want to confirm.

Also why is there a need to glue them? I saw this photo: http://www.diyaudio.com/forums/attac...amp=1171282640

The transistors are facing each other. But since I want to replace a 2SK389 with 2SK170, I cannot have them facing together unless I bend the pins to make it work?

thank you for the help

luvdunhill · 16th July 2007, 03:17 PM

yes, it's okay to use the single versions.

The devices are glued together for thermal coupling, which improves the degree to which the can be matched (not the best choice of words, but you get my drift).

I'd recommend about 15 of each single version to find 1 closely matched pair, as in my experience these can vary widely even with the same grade.

jarthel · 16th July 2007, 03:36 PM

I already have matched pairs. does this mean I do not need to glue them?

thanks again

h_a · 17th July 2007, 08:19 AM

C'mon! You need thermal coupling, otherwise your matched fets are going to drift thermally -> they're no longer tightly matched.

That's the reason the 2SK389 is a double package, tight thermal coupling and best matching since both fets are sitting next to each other on the wafer.

Don't worry about glueing them together. It would be nice todo if possible, but if you don't need the last bit of performance (then the 2SK389 would anyway the only choice) put them in and that's it.

Cheers, Hannes

jacco vermeulen · 22nd July 2007, 12:48 PM

fun stuff, watch the production date code : here

h_a · 25th July 2007, 03:46 PM

Oh Jacco, excuse my ignorance, but I fail to understand the production code. The datasheet also gives me no clue about what '7E' might mean.

Struck the lightening please. Cheers, Hannes

twitchie · 25th July 2007, 03:53 PM

Is that supposed to mean they were 'produced' in 2007?

I guess if they're fakes, it would be true, since they probably were made this year.

uli · 25th July 2007, 04:03 PM

Bought lots of SJ109 in 2004 - 2005, some of them carry 7E

does not mean 2007

Uli

jacco vermeulen · 25th July 2007, 05:18 PM

NEW/NEU ones from May '97.

h_a · 26th July 2007, 08:48 AM

Isn't it the same for Jfets as for wine?

The older it gets the better it is

16th July 2007, 03:12 PM	#1
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	2x 2Sk170 in place of 2SK389 and 2x 2SJ74 in place of 2SJ109? I've seen a reply where someone said it's okay to replace a 2SK107 with 2SK389 (same for 2x 2SJ74 in place of 2SJ109) but I want to confirm. Also why is there a need to glue them? I saw this photo: http://www.diyaudio.com/forums/attac...amp=1171282640 The transistors are facing each other. But since I want to replace a 2SK389 with 2SK170, I cannot have them facing together unless I bend the pins to make it work? thank you for the help

25th July 2007, 04:03 PM	#8
uli diyAudio Member Join Date: Dec 2002 Location: Vienna, Austria	Bought lots of SJ109 in 2004 - 2005, some of them carry 7E does not mean 2007 Uli __________________ 'Jazz is not dead, it just smells funny' F.Zappa

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16th July 2007, 03:17 PM	#2
luvdunhill diyAudio Member Join Date: Jul 2006	yes, it's okay to use the single versions. The devices are glued together for thermal coupling, which improves the degree to which the can be matched (not the best choice of words, but you get my drift). I'd recommend about 15 of each single version to find 1 closely matched pair, as in my experience these can vary widely even with the same grade.

16th July 2007, 03:36 PM	#3
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	I already have matched pairs. does this mean I do not need to glue them? thanks again

17th July 2007, 08:19 AM	#4
h_a diyAudio Member Join Date: Sep 2006	C'mon! You need thermal coupling, otherwise your matched fets are going to drift thermally -> they're no longer tightly matched. That's the reason the 2SK389 is a double package, tight thermal coupling and best matching since both fets are sitting next to each other on the wafer. Don't worry about glueing them together. It would be nice todo if possible, but if you don't need the last bit of performance (then the 2SK389 would anyway the only choice) put them in and that's it. Cheers, Hannes

22nd July 2007, 12:48 PM	#5
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	fun stuff, watch the production date code : here

25th July 2007, 03:46 PM	#6
h_a diyAudio Member Join Date: Sep 2006	Oh Jacco, excuse my ignorance, but I fail to understand the production code. The datasheet also gives me no clue about what '7E' might mean. Struck the lightening please. Cheers, Hannes

25th July 2007, 03:53 PM	#7
twitchie diyAudio Member Join Date: Jul 2004 Location: Toronto, Canada	Is that supposed to mean they were 'produced' in 2007? I guess if they're fakes, it would be true, since they probably were made this year.

25th July 2007, 05:18 PM	#9
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	NEW/NEU ones from May '97.

26th July 2007, 08:48 AM	#10
h_a diyAudio Member Join Date: Sep 2006	Isn't it the same for Jfets as for wine? The older it gets the better it is

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