Active FETs vs. Step-up phono stage designs

Thanks for that URL, Dave. I did not know about MAT12. I wonder if it is equally suitable to our application, compared to the MAT02.

Dear DHL, The late Allen Wright told me much the same thing about the scarcity of high quality discrete transistors that he experienced in building his two phono stages, FPV and RTP. I was implementing a hybrid dual differential cascode input stage in my own phono stage, and AW advised me to try the MAT02 bipolar for the bottom active element in the cascode. With some effort I finally found some, and I bought a bunch, just in case. But when I asked AW why he was not using that part in the RTP3C (or whatever), he said he could not afford to risk it because of the difficulty in obtaining a stockpile for production and future repairs. The MAT02 had already been discontinued at that time. As I understand it opamps and other ICs are also constantly being discontinued in favor of newer types that offer some real or imagined advantage.

The MAT02 certainly lives up to AW's opinion of it in the context of my preamp. I have two extra pairs, just in case. (As you know, the MAT02 is a dual section device, so one of them suffices for each balanced channel, and the section matching in terms of transconductance, etc, is way better than one could hope for in a dual section tube, plus it stays that way over time.) Everything else downstream is tubes.

I guess I would be reluctant to buy $15,000 worth, in hopes of selling the extra ones to "friends". Even for a manufacturer, that would be a lot of investment for one part. But generally if you search diligently you can usually find a vendor who is willing to sell parts in low volume.

Interesting addendum. I received an issue of TAS yesterday that contains a roundtable discussion of amplifier and preamplifier design by a collection of well known designers, e.g., Rowland, Pass, Curl, Carver, Lamm, etc. It's mostly self-serving drivel, a la TAS, but at least one or more of the panel notes that "audio grade" solid state devices, meaning devices specifically made with a view to no compromise audio component design and build, are becoming ever more scarce. He fears that his work will eventually be hampered by sheer lack of the optimal parts. Other panelists were more optimistic, however.