MichaelW
Well-known member
In my post for the first Sheepy Love SMD Phase 90 I mentioned that I had ordered 100 Toshiba 2SK208-GR SMD jfets.
These are the SMD equivalents of the 2SK30A Jfets that were used in the Boss PH-1 and PH-1r phasers.
So I'm mixing metaphors here by using them in the MXR phasers which originally used the obsolete 2N5952 JFETs, which are difficult to find in sufficient quantities to get a matched set.
I also made the statement that RG Keen said in his Jfet matching article that the ideal VGS@10k values should be 2.5-2.6v. This is incorrect, he never said that.
I don't know HOW I managed to read that INTO the text of his article (eisegesis) but I'm going to blame it on the cancer, or the meds, or something...........
That's my excuse and I'm sticking with it hah!
I also learned something! RG Keen's JFET matcher isn't measure VGS off but rather VGS@10k. So I'm correcting my nomenclature going forward.
Ok so back to my phaser monologue. If you read my other build report you'll recall that at the time all I had in bulk were MMBF5457's. Which are excellent substitutes for the 2N5952 TO-92, If one can get a matched set. It took me opening and testing over 50 jfets to get a matched set.
This in turn blew up the myth about how SMD transistors were supposed to have tight tolerances. Much to the chagrin of @Harry Klippton and @jimilee.
There was much weeping and gnashing of teeth and wringing of hands.
Well fear not my brothers, I bring good news of joy and celebration. I took my roll of 100 2SK208's and cut a strip of 10 to begin matching with my handy dandy modified RG Keen matcher and the first 4 I opened matched at 1.6v. The rest of the 6 out of 10 also matched!
So it seems that SOME SMD transistors, like the MMBF5457 have more variance than others. the 208s seem to be pretty tight.
Anyway, I built a second Phase 90 using the 208s and it sounds lovely. I've been comparing it to the first one I built and I like it better, by a slim margin.
They both sound great!
I went with the same color enclosure (I just happened to have another one) and knob as a nod towards the original MXR.
I used my easy bake hot plate to solder the JFETS in place. I'm still trying to get the hang of using solder paste. I can't seem to get the right amount of it on.
But they worked.
Next up I have an SMD Jfet Phase 45 project from @szukalski aka Sheepy Love. I shouldn't have any problems matching 2 JFETS hahaha. Stay tuned.
These are the SMD equivalents of the 2SK30A Jfets that were used in the Boss PH-1 and PH-1r phasers.
So I'm mixing metaphors here by using them in the MXR phasers which originally used the obsolete 2N5952 JFETs, which are difficult to find in sufficient quantities to get a matched set.
I also made the statement that RG Keen said in his Jfet matching article that the ideal VGS@10k values should be 2.5-2.6v. This is incorrect, he never said that.
I don't know HOW I managed to read that INTO the text of his article (eisegesis) but I'm going to blame it on the cancer, or the meds, or something...........
That's my excuse and I'm sticking with it hah!
I also learned something! RG Keen's JFET matcher isn't measure VGS off but rather VGS@10k. So I'm correcting my nomenclature going forward.
Ok so back to my phaser monologue. If you read my other build report you'll recall that at the time all I had in bulk were MMBF5457's. Which are excellent substitutes for the 2N5952 TO-92, If one can get a matched set. It took me opening and testing over 50 jfets to get a matched set.
This in turn blew up the myth about how SMD transistors were supposed to have tight tolerances. Much to the chagrin of @Harry Klippton and @jimilee.
There was much weeping and gnashing of teeth and wringing of hands.
Well fear not my brothers, I bring good news of joy and celebration. I took my roll of 100 2SK208's and cut a strip of 10 to begin matching with my handy dandy modified RG Keen matcher and the first 4 I opened matched at 1.6v. The rest of the 6 out of 10 also matched!
So it seems that SOME SMD transistors, like the MMBF5457 have more variance than others. the 208s seem to be pretty tight.
Anyway, I built a second Phase 90 using the 208s and it sounds lovely. I've been comparing it to the first one I built and I like it better, by a slim margin.
They both sound great!
I went with the same color enclosure (I just happened to have another one) and knob as a nod towards the original MXR.
I used my easy bake hot plate to solder the JFETS in place. I'm still trying to get the hang of using solder paste. I can't seem to get the right amount of it on.
But they worked.
Next up I have an SMD Jfet Phase 45 project from @szukalski aka Sheepy Love. I shouldn't have any problems matching 2 JFETS hahaha. Stay tuned.
