Anyone compared BAT Rex vs. Atmasphere MP-1?

Raquel, I think with older tubes the quote might be accurate. But with modern signal tubes, particularly low level miniatures, there is a phenomena of grid contamination that has to do with the inclusion of contaminates during the assembly process. An excellent example is fingerprints when workers are not given latex gloves or the like for assembly.

In such cases (if you are using tubes with this or similar issues) leaving the preamp/amp on 24/7 is not really all that helpful, as when the grid contaminates the transconductance will fall off sharply.

Its really not a good idea to design for tubes that are out of production, unless as a manufacturer you have no concerns about the owner being able to find tubes for the unit 20 years down the road. IOW its a good idea to design for tubes that are currently being made, so using such tubes has become a fact of life.

We have seen this contamination problem with 6SN7s, 12AT7s, 12AX7s, 6DJ8/6922 and a few others. It is considerably more rare with NOS types.

I'm just pointing this out because 24/7 as a generalization is not always the panacea for best performance.

As an additional FWIW, the issue of cathode stripping is far more pronounced with power tubes. It is a matter of controversy as to whether its a problem for small signal tubes.

"will indeed t ... urn everything off." Sorry about that.

Messrs. Karsten and Komenkho: Great stuff - thank you. I look forward to the debate about cathode wear and small-signal tubes the next time you sit on a panel together!

Darkmoebius,
This is a very abbreviated version of my experience with the above preamps:
Supratek: dynamic, fairly resolving and involving, but is not completely neutral- it did have very annoying (to me) mid range glare on certain recordings. After many debates I suspect, that it suffered from some kind of chassis generated resonance (it does have fairly thin metal bottom plate), and some members reported improvement of the glare with the use of the wooden part of the chassis for support.
Nagra: very refined, involving and musical. It does have slightly different (forward) soundstage perspective, but is not bright.
Doshi: neutral and well balanced, but left me with an impression of lacking dynamic impact, compared to Supratek and Nagra, and especially to REX.
REX: It does NOT have any flaws IMHO- extremely dynamic, beautiful tone, very balanced (no pun intended), mid range is absolutely to die for, resolution in spades, bass, you name it- it does it all. Overall, it's a different class of music reproduction, compared to others.
I lied, it does have a few flaws- it is line stage only, hence an additional expense of the separate phono,
it runs pretty warm,
and it costs $22k now.
I still feel, one day I might have it in my system again, it was that addictive.

09-01-10: Maril555
REX...I still feel, one day I might have it in my system again, it was that addictive.

Oh my, that just feeds into my obsession.

Just to add my 2cents for this duscussion..

I'm a happy owner of BAT 52SE (a "little brother" of REX). I would also describe this "house sound" as breathing transients, superb textures and very resolving. Nothing compared with usual "tube coloration" as probably one likes. Just pure music window... It's so amazing clean in my system even with relatively cheap Proak D15 speakers.

Never read an average review for REX - it is outstanding always.