Question for Amp Designers

We have two Class AB amps with the same power.

One is described as fast, lively, & forward.

The other is described as laid back, mellow, & slower.

What in the design gives these two amps the above sound signatures?  
"Have you heard this for yourself or are you going by what someone else said?"
"I think its fair to say that we hear it all the time in the world of audio. "

Maybe. But if the OP was going by other people's comments and not by his own observation, then we don't know if the amps really sound like that. There may be no problem at all.

" Yeah, too bad we can't get Julian Hirsch in here to answer this one!"

I'll answer for him.

"We put this amp through our most rigorous tests, and here's what we found out. 

For the first test, we pushed the power button. It passed with flying colors. The amp lit up like a Christmas tree.

The nest test was for sound quality. It passed with flying colors again. We know that all amps sound exactly the same, and this amp was no exception.

In conclusion, we give this amp our highest recommendation. It performed flawlessly during all of our tests. If you're looking for a state of the art amp, this is the one for you.

Maybe. But if the OP was going by other people’s comments and not by his own observation, then we don’t know if the amps really sound like that. There may be no problem at all.
But the OP has said both in this thread. In his initial post that posed the question and then with his own observations....
I’ve heard it with my own amps. I have 3 systems in my house and for some strange reason I Iike to swap out pieces to hear the changes.
Now I am not in the camp that says all amps sounds the same. IMO, they don’t. Nor am I an electrical engineer. But I have also wondered how some can be described as warm, laid back, etc. while others are forward, lively, etc? Especially when comparing two different brands of amps with a near identical power output rating, bandwidth and THD. I have been told this in the past when selecting my own gear. For example, I have been advised many times, on this board and others, that my Marantz PM15S2 is warm and laid back and shouldn’t be paired with warm speakers like Vienna Acoustics or Sonus Fabers.  Why?  It has the proper output to meet a 4 ohm speakers needs in an average sized room.

So again, what exactly do the designers do to give an amp a signature sound that would earn these attributes by both audiophiles and those who sell them? And yet maintain the same low THD at all frequencies for its rated output?