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In the Forum: Analog Playback
In the Thread: The K&K SE hybrid phono stage: a report
Post Subject: New MOSFETS and New AdjustmentsPosted by Paul S on: 10/4/2009
Another K&K user contacted me recently, and he subsequently sent me new MOSFETS to swap with those I had in my unit.  Original MOSFETs were Supertex DN2540.  New MOSFETs are IXSYS 1N100D.

The only reason I swapped these was out of curiosity.  The other guy said it was "magic", and I wanted to hear for myself what that meant.

The swap required that I remove two of the three boards in my older unit, along with the big Cardas caps and one ground wire, in order to get the MOSFETs out and in without doing a lot of colateral damage.  Another thing I had t do was re-trim the 6922 filament current that was raised too high by the MOSFET swap.  I put shrink tubing on a small, plastic-handled screwdriver in order to avoid shorts while working in the crowded space while the K&K was energized.

The other guy said he'd settled on 1.68V for the new value.  I found this value made my own upper midrange too prominent, so I backed it off to 1.6V.  After an hour of listening (with the unit settling down) I dialed it back up to 1.62V, for an increase in sonic "benefits".

Overall, I like the change.  There is greater clarity and better articulation, with no penalties.  There is also a greatly increased sense of "height" in the soundfield, and the entire soundfield is larger.

This is the first time I have messed with any of the operating values in this unit.  In fact, I never really thought about it much until the new MOSFETS arrived.  Now, I am very interested to continue experimenting with this variable.

These changes do not seriously affect the K&K's character, but they are significant.  I will add to this when I have had more time with the altered unit.

Yes, it has occurred to me that the change in operating values might have more to the changes in sound than the new MOSFETS do.

FYI, this is a K&K "approved" change.

Paul S

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