Anyone compared BAT Rex vs. Atmasphere MP-1?

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.

Thank you, Mr. Karsten. Incidentally, does your MP-1 use solid-state rectification, and I wonder what the voltages are, relative to maximum recommended voltages, on the 12AT7's and 6SN7's (BTW, are the 6SN7's standard or GTA/GTB's?)? If this information is proprietary or you do not wish to respond for whatever reason, my apologies, I do not mean to pry. My question goes to the issue of tube life and running the unit 24/7 - I would think, assuming moderate voltages and solid-state rectification, that 24/7 operation on this preamp would maximize tube life. My rationale for this is set out in my comments to the following thread:

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

Best regards.

The preamp is designed for 24/7 operation. IMO you get better bang for the buck when the preamp is operated when you are playing music, rather than using up the tubes while you are at work or asleep in bed.

It warms up quickly, much faster than in years past, due to better regulation and better coupling caps. Two hours is more than enough for the preamp to settle out so 24/7 operation really doens't win you anything with it like it did 10-15 years ago.

The power supplies (8 of them) are all tightly regulated so the use of SS or tube rectification isn't relevent; the rectification is all handled by HEXFREDs. The highest voltage drop on any tube in the unit is about 150 Volts, the B+ and B- are both regulated at +/- 250V.

The 6SN7s in the unit tend to last about 10,000 to 30,000 hours (GT, GTA or GTB, although seriously we don't know how long the 6SN7s last; some seem to last literally for years). The 12AT7s (used only in the phono) tend not to last as long. IF you run the preamp 24/7 we used to recommend replacement of the 12AT7s every 4-5 months; in the Mk 3.1 (the latest version IOW) they seem to last considerably longer but the preamp is so recent (came out a year ago) that we don't have good numbers on that.

Mr. Karsten: Many thanks for your responses. The 6SN7 Sylvania chrome tops in my VAC Renaissance amp, used as driver and splitters, are beginning their eleventh year of use (in on/off service), and for all I know, they may have previously seen service in somebody's T.V. :)

Just a couple of quick notes here, don't mean to overburden the forum.

One - regarding the extended tube life with 24/7 operation... while a common opinion, it is most definitely not universally agreed upon or shared. One could construct many different cases, but in my opinion, in ***general*** in normal home environment turning the equipment ON and OFF will produce longer tube life.

Furthermore, continuous operation will, without any doubts, shorten the life of most electronic components. Whether this is justifiable by potentially shorter readiness times - is up to the individual user to decide.

Regarding the 5AR4 tubes - their quality level is generally quite high, but we certainly went through a less than spectacular batch. As the manufacturer, we do our best trying to shield the customer from such problems, but that is not always possible in timely fashion. For instance, we stopped using the Sovtek 6V6 tubes entirely, at one point. But some problems only manifest themselves weeks or months down the road.

All tubes in BAT equipment operate with very significant deratings. The output 6C33 tubes operate the hardest, at about 60% of maximum stress, other tubes are typically used at far less than 50%.

Victor Khomenko
BAT