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In the Forum: Analog Playback
In the Thread: The K&K SE hybrid phono stage: a report
Post Subject: Tubes (etc.) vs Phono CurvesPosted by Paul S on: 10/9/2009

Rooting around for manufacturers' operating curve/info on 6922s I came across a short paper I got years ago from electronics genius Roger A. Modjeski.  In a nutshell, RM talked about internal variables in tubes that affect their electrical characteristics, and hence their sound.  He specifically mentioned the effects of ESR and other electrical paramenters on circuits, along with inevitable EQ shifts resulting from the individual tube's effect on loop gain due to its simple and in-circuit gain characteristics in RIAA circuits.  Cold water in one's face, to say the least.

To think of tubes like this certainly puts a new twist on old observations about new vs NOS tubes, or one brand vs another in a given circuit.  And since no "circuit" is complete until the fat lady sings, this is effectively causing me to re-think my approach to tube selection and use.

I actually prefer to use SS wherever I think I ccan get away with it.  Since I have been unable to get around tubes for certain applications, perhaps I will go back to where I was with the AI M3A, which is to say, open to experimenting with operating points.

Regarding RAM's own "products", it may have been about 1988, or thereabouts, that I "heard" Modjeski's original RM-9 amp and RM-5 phono-preamp.  I bought the amp because it was dead neutral; and I actually passed on the phono-preamp for the same reason...

I put this post in with the K&K because of my previously-stated idea that changing operating points might be the biggest difference between the MOSFETS in that unit, and RAM's ideas seem to build on those thoughts.

Paul S

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