The following intrigued me, could you elaborate?
Quote:
Originally posted by ToneLux
...I never liked the 990 design, as it had too many internal compensation things to keep it stable.
|
By my count, the 990 has 5 components wholly devoted to high frequency stability. I'm not sure it's fair to count the emitter resistors and inductors used in the input diff amp, but even with them included there are only 9 "compensation things".
I've seen some schematics that purport to be of the 2520, and if they're anything to go by, that circuit appears to need 8 components to keep it stable. An RC network across the output of the first diff amp, a cap that effectively makes the HF signal path single-ended, an RC snubber across each driver transistor, and the usual compensation cap. Am I understanding the 2520 circuit correctly, or am I missing something?
Nitpicking of parts count aside, I'd be very interested to hear your thoughts on op-amp topology and compensation in general, and which design choices you believe translate most directly to good sound.