This would be an issue of semantics. I'm of the opinion that tube
saturation doesn't suddenly kick in once the power levels reach a
certain
proportion of tolerance, and that even at low levels the effect is
present.
If what I'm hearing at low levels isn't a result of the same properties
that
are influencing the sound near full saturation, then I'm not sure I
care.
My point was that tubes are not a benign audio component at any output
level.

Neither is a transistor. However, when properly used, both are quite
transparent and uncolored, particularly in a preamp.

Well my argument is that certain coloration lends itself to transparency
better than neutrality. If it's possible to render a neutral response from
a tube amp, then why haven't I ever run into one? Granted, many models are
geared to accentuate coloration beyond what I like, but the fact remains
that neutral tube amps don't seem to be especially popular.

If you mean that I couldn't fix a tube amp to save my life, you're
right. What I can do is hear the difference between different brands
and/or vintages of the same tube in the same amp. But hey, if you've
got the fancy diagnostic gear that says tubes don't color sound then I
guess I'm trumped. Funny how I keep running into all these defective
tubes that *all sound distinctly different at any output level*.

No, you are running into gear that is operating the tubes "way off their
curve". If you bias a transistor improperly (and don't use any corrective
feedback), guess what?

You end up with a boring neutral response? Fantastic.

If you mean audio engineering, I know enough to use tubes for coloration
effects, and to not use a tube amp for monitoring, instead to go the
"accuracy" route to better appreciate how the mix will sound on a
variety of gear, rather than just my own system which is tailored to my
preferences. On this matter I am not alone. I think I'll stick with the
engineering practices of the last 25 years rather than blindly follow
the numbers generated by a simulation gadget.

Engineering practices? What kind of "engineering" are we reffering to?

Audio engineering, as in recording, mixing, mastering, which I've been doing
for 7 years.

I have got to ask - what kind of gear are you using to "color" the sound?

In the studio, whatever's handy that does the trick. I'm often work out of
other people's studios, so too many models to list, and at home I've got a
DBX 386 (nothing outrageous) which has a reasonable tube circuit to play
with, none of which are geared for neutrality either. Ironically I do less
tube-swapping in the studio than I have at home.

At home I've taken over a year to find the right arrangement of preamp tubes
in my Audio Innovations S500 (25W/ch pure class A 5-stage preamp and
push-pull EL34's) for my particular tastes. I know two others with the same
amp locally, and they prefer different tube combinations to mine. We've
swapped tubes between amps before, and I even swapped amps with a friend
because I prefered his older model to my newer one and vice versa. The
experience has left me with the impression that the three of us literally
hear things differently since we each go after the same qualities -
transparency, imaging, timbre, etc. I've settled on three late-60's vintage
Telefunken ECC83's followed by two RFT PCC88's in the preamp and I've got
the original mid-80's Mullard EL34's now but might try others in time.

The other stereo tube amp I'd know best is an H H Scott 299B, which was
overly warm and I'm not keen on 7189's. I've got several guitar and bass
amps as well, but the only rig that deserves any attention here would
probably be the class A preamp in my Ampeg VT-22, which is pretty wild using
12AX7's, a 12AU7, 6K11, 6CG7, then a 12DW7 driver. I think it was designed
with neutrality in mind, then the class AB poweramp using 7027's with 525V
plates warms things up. Haven't toyed with that one much yet, I like the vi
ntage tone from the original caps which have surely gone way off-spec after
33 years.