Pros and Cons of built-in amps?

Anybody who does not hear diffrences between a SET amp (any one) and any class A or AB solid-state amp is either:

1) Listening to a very unresolving system.

2) Using the SET on inappropriate speakers (in which case it should still sound different, but bad).

3) Listening to very poorly recorded music.

4) Not listening carefully.

5) Does indeed have poor hearing or at least is poorly acquainted with the sound of live, unamplified acoustic music/vocals.

6) More than one of the above.

I will go far enough as to say this is a statement of fact. It certainly isn't intended to be inflammatory or personally degrading to anyone.

I would also say that the quality of the SET here is not too paramount as the poor quality ones will have problems - like rolled-off extremes or noise - that should still be *audible*, and will still have much or most of the characteristic single-ended tube sound.

I have listened to some push-pull tube amps *with moderate feedback* that do sound A LOT like a typical push-pull solid-state amp, but single-ended tubes with little to no feedback are quite another thing.

03-25-08: Bob_reynolds
In the system I was talking about I've had a tube SET amp and two different solid state amps. I heard no difference (except on some days the tubes made audible noise).

That statement summarizes everything that one needs to know about you Bob. You might make that quote your tag line. You bring nothing of value to this discussion.

Are we sure that studio use active speaker for sound quality reasons? Maybe it's for convenience or something else.

Try proaudioreview.com (?) and they commonly rave about the sound quality of passive speakers running Chord or Pass amps.
I prefer active speakers, but don't really think "sound quality" as audiofiles define it is what studios have in mind. More like:
1) Mixes that will sound good on a variety of stereos.
2) Elevated presence region to better hear faults in the recordings.
3) Ability to play super loud. Like 110-120dB all day.
4) Reliability: play at 110++dB ALL day without a breakdown.

Things like:
1)"truth of timbre".
2) grain-free sound
3) not bright highs
4) dynamic range
5) attack and decay
6) "air and space"
7) "fleshed out" sound

are important for home listening but less so in the studio.

Cdc mentions that a pro audio review site really likes Chord and Pass Labs amplifiers. That's encouraging as they are both excellent examples of how good solid state amps can sound.

But it also points to a limitation with active speakers like those from ATC and Meridian. As good as both of those are, they are limited by the quality of their built-in amplifiers. In Meridian's case, which I would argue has the better amplification of the two, they are not at the same level as the Chord amplifiers. I know this because I used to be a Meridian dealer and have recently spent a fair amount of time with Chord electronics. Chord makes some of the best solid state gear I have ever heard. (I am not a Chord dealer)