Anyone compared BAT Rex vs. Atmasphere MP-1?

I would like to ask Raquel to elaborate on the Rex not being able to be on 24/7. The reason I ask is that I have mine on 24/7 (breaking in new speakers) and you have me worried. :-)

Madflloyd:

Some tubes in some tube power supplies can pass a relatively large amount of current and will wear out like output tubes in a power amp will wear out (certain tube preamps actually use output tubes in their power supplies - the ARC Reference 3 uses a 6550, and I believe the big multi-chassis Jadis used to use EL-34's). For example, when Stereophile reviewed the BAT Rex, they went through a couple of 5AR4's in the power supply over the course of several months of leaving the preamp on 24/7 (which they evidently did at BAT's suggestion). The review suggests that the BAT is fused to protect against tube blows in the power supply - you need to consult your owner's manual or ask BAT whether 24/7 operation poses a safety issue.

The other circumstance in which I would tend to think twice about 24/7 operation in a piece of equipment using small-signal tubes (i.e., tube preamps, tube DAC's, tube tuners) is if the tubes are run near their maximum voltage rating. Basically, such a tube will face the same wear issues that an output tube in a power amp will. It did not escape me that the Rex is said to run really hot, but this could be nothing more than the fact that it has a ton of tubes in it - I don't know how its various tubes are run relative to their maximum voltage ratings.

If, however, a tube preamp has solid-state rectification and does not feature a hot-rodded tube circuit (that would be the vast majority of them), I will run it 24/7 in order to maximize sound quality and tube life. As for why 24/7 operation would extend tube life, please see my comments about small-signal tubes and tube performance in the following thread:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1281657617&&&/VAC-Signature-MK2a-w-phono-users

I hope this helps.

Rtnl:

You wrote "Raquel, just for clarification, the BAT should be left on standby when not in use?" I cannot answer this question - you would have to ask BAT.

Again, it is generally much better to leave tube equipment featuring small signal tubes turned on 24/7 in order to maximize tube life, but as explained above, if the piece features tubes in the power supply like the BAT Rex, or operates the tubes in the circuit near their maximum voltage, you may be better off turning the unit on and off.

When you write "[N]onetheless, something must have been not quite right, and I agree to burn-in the unit for a few hundred hours for a review.", I'm afraid I do not understand the idea that you are trying to convey.

My apologies to the author of this thread for the tangent about tube maintenance. As to how this issue applies to the two preamps you have inquired about, the Rex has been discussed. As for the Atma-Sphere, I'm pretty sure it uses solid-state rectification, which, in combination with its use of 12AT7's and especially 6SN7's (they were used in televisions and are extremely robust), would make me run it 24/7. If it were me, I would probably run a Rex 24/7 notwithstanding everything written above unless BAT strongly disagreed, but based upon the Stereophile review, it looks like BAT has no problem with 24/7 operation of this preamp.

No problem with minor tangent of discussion, Raquel, as long as it is informative. And your points fit that definition to a "T". You have given me a lot more to look into before making an expensive leap.

I still need to nail down which speaker genre I want to explore(having tried SET & high(er) efficiency wide-range driver) - electrostat/ribbon, line array, multi-way cone driver. I'd like to try a fully balanced/differential system from source to speaker. But, that may be hard when it comes to phono preamps(except maybe Atma-sphere)