Subbing 2SK389 for 2SK170

leadbelly · 14th April 2008, 05:44 PM

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?

mlloyd1 · 14th April 2008, 06:39 PM

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.

mlloyd1

satoru · 14th April 2008, 07:22 PM

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!

Satoru

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14th April 2008, 06:39 PM	#2
mlloyd1 diyAudio Member Join Date: Feb 2001 Location: illinois	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. mlloyd1

14th April 2008, 07:22 PM	#3
satoru diyAudio Member Join Date: Jan 2007 Location: Berkeley, California	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! Satoru