A case in point, I decided to spend the day seeing if I could match the 2005 Pass labs Single Ended Transistor sound with that of the 1995 recapped Threshols T-400. On the surface, they have a rather different sound, with the T-400 seeming dryer and less bouncy in this room. Jcarcopo once called that amp's bass "relentless".
Looking over my room correction curves, listening, and applying very tiny amounts of dsp (adjustments in the 1/100th of a db at a time) I discovered that the "dryness" was that the IGBT of the T-400 has quite a bit lower impedance at 20hz than the Pass's mosfets (relative to the rest of the spectrum) , so has a bit too much 20-40hz relative to the Pass. Thus filter errors on the room eq showed up MUCH more clearly (by ear) than on the Pass. And, yes, I got all but the difference in in presentation of dynamics between single ended and PP amps. Fun work.
Looking over my room correction curves, listening, and applying very tiny amounts of dsp (adjustments in the 1/100th of a db at a time) I discovered that the "dryness" was that the IGBT of the T-400 has quite a bit lower impedance at 20hz than the Pass's mosfets (relative to the rest of the spectrum) , so has a bit too much 20-40hz relative to the Pass. Thus filter errors on the room eq showed up MUCH more clearly (by ear) than on the Pass. And, yes, I got all but the difference in in presentation of dynamics between single ended and PP amps. Fun work.