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Old 14th April 2008, 05:44 PM   #1
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Join Date: Dec 2002
Location: Calgary, Alberta
Default Subbing 2SK389 for 2SK170

I don'y really know a whole lot about discrete SS, so here's my question.

I'm looking at building a Pacific phono preamp (schematic attached).

I have both SK170's and SK389's on hand to build it. If I were to sub SK389's into the circuit, would thermal coupling provide more benefits if (a) each SK389 were split across the stereo channels, or (b) each SK389 were split across the 2 stages of a single channel? Or is it not a good idea?
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Old 14th April 2008, 06:39 PM   #2
mlloyd1 is offline mlloyd1  United States
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in my humble opinion, this circuit would not take advantages of the matched characteristics and thermal tracking capabilities of the 2sk389 dual jfet in either of your suggested scenarios. save your 2sk389 parts for a more beneficial application; use the 2sk170 and be happy.

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Old 14th April 2008, 07:22 PM   #3
satoru is offline satoru  United States
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Hi leadbelly,

I don't think you want your input and output stage JFETs to be thermally coupled, nor left and right channels. So, better off with 2SK170. More important to pick one with Idss ~ 5mA (that sets the voltage on JFET) that sets the voltage here and there. Good luck!

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