Active FETs vs. Step-up phono stage designs

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.

Lewm:

I think that part MAT02 is the same part I was refering to. As the older analog device producers get aquired by larger companies, many of these parts get lost in the shuffle, unless the customer starts screaming. Couple that with the fact that fabs for discretes are becoming more expensive to maintain...not even the Chinese want to make discretes. Large power transistors are still available, but small signal are getting tougher to find.

Suprisingly, many of the early op amps are still available, probably due to replacement requirements in military and industrial equipment. All the late 70's TL070 and 080 series are still with us, as are the the very first 741s. But special parts from Burr Brown and PMI have dissappeared.

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.

The discontinued MAT02 is replaced by MAT12.

http://www.analog.com/static/imported-files/data_sheets/MAT12.pdf

Like Lew I use this at input of phono in the bottom of a hybrid cascode. It provides huge gain, low noise, and great sound.

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.