Please help me understand


There are two concepts I've never been able to reconcile. How is it possible for different amps to have similar distortion levels (inaudible), yet still have what audiophiles might describe as a "tonal signature". In other words, how is it possible for an amp to have a perceived "warm" or "bright" sound, if it's accurately reproducing the input signal? It seems to me that all high quality, properly functioning amps should sound the same. If they don't, them some of them aren't doing their job very well.
danoroo
Dynamics.slew rates. current vs.voltage are some things that come to mind that will affect sound and not distortion figures.
As I understand, the way THD is measured involves measurement with a simple resistive load -- for example, an 8 ohm resistor. But speakers are not resistors. At the very minimum, the measurement doesn't fully capture what's going on.

Also, this is an interesting article:

http://www.passdiy.com/pdf/distortion_feedback.pdf
Two cars both have the same tires, but one is noisier on the road... different type outputs have their own character, different capacitors have the own, different resistors, the amount of and type of wire in a circuit sound different. Not to mention circuit layout. It would not be unusual for two identically spec'd amps to sound quite different.
Two cars both with 250 horsepower, but one clearly is faster than the other, one handles better, brakes better etc. Alot goes into engineering.
The measurements we can make are obviously not complete. Science is not perfect or tells the whole story. Everybody thought all cd players should sound alike because after all bits are bits. Then someone discovered jitter which can alter digital sound. If you can hear a difference but can't measure it it does not mean the difference doesn't exist.
The same way it is possible for two people to have the same height, weight and close size but look completely different. THD is a small part of the story.