Anyone compared BAT Rex vs. Atmasphere MP-1?

Raquel, just for clarification, the BAT should be left on standby when not in use? Just not 'on' 100% of the time. One could turn it off if going away for some time.

I thought the initial surge of current into a cold tube was the detrimental factor.

I also hear no sonic difference within 5 minutes of coming from totally off, vs. 5 minues of coming out of standby.

I'm not sure why Stereophile had problems with the 5AR4s. These Sovtek tubes cost $20 each, so it is not a big deal. Nonetheless, something must have been not quite right, and I agree to burn-in the unit for a few hundred hours for a review. Also, it is practically unheard of for a NOS GZ34 to die. Some of these have been in operation for a few decades.

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)

Darkmoebius:

I can think of a few other fully differential balanced phono stages: BAT, Einstein, Rowland. I run a Rowland Cadence.

Raquel, the way the MP-1 works is it has a direct-coupled output. The output impedance is low enough that it can drive 32-ohm headphones easily. It is designed to drive 600 ohms without effort; obviously its output impedance has to be well below that in order to do so.

Because its outputs are direct-coupled, the output impedance is flat from 1Hz to 200KHz or thereabouts. So it really can drive 200 foot interconnects without difficulty.

It my opinion that getting rid of the output coupling caps is the single best thing you can do with a tube preamp to improve transparency and bandwidth.

The MP-1 was/is the first balanced line preamp for high end audio. Victor's business partner bought one of the first production units before they went into business together. He had some of our MA-1 amplifiers too- we still have his warranty forms on file.