[quote author="mediatechnology"]
* Then of course there's NSC doing the opposite putting modern op amps in TO packages which has me really stumped.[/quote]
My guess is that they got audiophile feedback about how much people like to see metal cases. I remember when such folk would pop the hood on a preamp from somebody with high-end pretensions and see those NSC dual FETs in DIP-8, and sneer that they were using evil dirty opamps :razz: When it's a metal case it seems to be less objectionable.
Funny thing is I believe, and I seem to recall Bob Pease said, that the plastic is often lower leakage and loss than the borosilicate kovar sealing glass, the latter being a significant noise contribution for charge amplifiers. When TI still was in the discrete biz their 2N4416s were the best---not just because they were very good chips, but because the construction of the package had the minimal volume of glass surrounding the gate lead.
This could actually have bearing on condenser mic pres, if it weren't for the likelihood that the capsule is a far more important dielectric loss source. And of course probably many other noise sources dominate that, including thermo-mechanical noise in the diaphragm and almost always ambient acoustical noise.
At one point Siliconix had some little ceramic packaged JFETs that I hoped would have low packaging loss. But alas, they weren't very good chips, and also possibly the cement they used to seal the package was lossy.