ricardo said:
Later era tube preamps in general; virtually all have stiff PSU and 20+dB NFB. I'm a tube preamp collector, have used probably 30 types to some degree, and am very familiar with over a dozen American types. I don't own any that would be considered PA or consumer grade, like the later Altec green panel stuff with plug-in transformers. All are employed in making records at my studio, on client dime. While I appreciate the later types, which do have their own sort of sound, they tend to be so much closer to SS that I seldom pick them. And they splat like SS; sometimes worse, I think. Later types tend to end up on drums that need a softer cleaner sound, like a honky-tonk band doing Bakersfield type country tunes. In reality, I'll use any of them for almost anything, but when a garage band wants to invoke Little Richard or Jerry Lee Lewis, the front end has got to smack the wall in a cool sounding way, which the later stuff just won't do. What was this thread about, again?
Relating to Ian's thread concerning DC stability in NFB preamp design, someone mentioned a comment I'd made about the WE 141A, which is a switched NFB design. It's harmonic character changes radically with gain adjustment (30 dB range, I recall). So NFB limits you if you want adjustable gain, simplicity, and remotely similar sound across the gain range. Many program amps will have an open loop stage hitting a volume pot, then an output amp with loop NFB. This gets you somewhere in between, but still gives a splat when stage one overloads stage two on unexpected peaks.
