Anyone compared BAT Rex vs. Atmasphere MP-1?

Mr. Khomenko:

Thanks for the input on the issue of tube life and 24/7 operation. My experience is that, while most people are aware of a debate regarding 24/7 operation and solid-state gear, few people who own or sell tube gear are aware that some manufacturers advocate 24/7 operation of equipment using small-signal tubes in order to extend tube life (my posts on this issue tend to create surprise).

Assuming the conditions necessary for 24/7 use are present that I describe in the links referenced in my posts, the only thing I worry about operating 24/7 with either solid-state equipment or small-signal tube gear (aside from not being home to disconnect equipment when an electrical storm passes through) is what it's doing to the caps, which tend to be rated for only a few thousand hours, but caps will often far outlast their ratings and are relatively cheap and easy to replace, while thermal cycle damage to transistors from on/off operation, particularly where the transistors have gone out of production and the amp thereby becomes worthless, or thermal-cycle damage to irreplaceable, cherished NOS small-signal tubes, is not cheap. If I owned BAT gear (and I may one day, as my system is fully differential balanced from turntable to amps - that's why this thread, about BAT and Atma-Sphere gear, caught my eye), I would follow your instructions and turn my equipment on and off. With all due respect, however, your advice does run contrary to the evidence I have described in my posts referenced above and in numerous other posts I have made over the years here.

As usual, this thread deviated from the original question- comparison of BAT REX and Atma Sphere MP-1 (MK III?).
I'm another one who would be interested in this topic.
As many others here, I've had BAT REX in my system for a significant period of time, and so far, it's the best preamp I've ever heard (others include Supratek, Nagra, Doshi).
MP-1 I only heard under show conditions, so I have no opinion really. It's intriguing to me, since it's a full-function preamp.
So, maybe somebody could offer an opinion on it? At least not in direct compar. with REX?

Hi Raquel,

This is the question that does not have a simple answer. As one of my teachers used to say - when in doubt whether simple rules apply, consider the extreme cases. Would you keep your units on 24/7 if you only listened to them for two hours once a month? Probably not. We, therefore, can safely assume that for the multitude of applications and uses there also exist multitude of correct answers.

There are several kill mechanisms acting upon the tubes (and other components), and you correctly mentioned one of them - thermal cycling. However, there are others. Of them the cathode wear might be the most important. Needless to say, both the full operation, and the typical Standby, have the cathodes working, and therefore wearing out.

Furthermore, as is known from the reliability studies, temperature always accelerates the component failures. Its effect is exponential, and its degree varies depending upon the component's nature, but it is always there.

Also, while it is true that thermal shocks are, generally speaking, damaging, it is the rate of change that is the most critical aspect of that particular effect. There are special accelerated life tests that include high rates of temperature change, and they have been shown to be effective predictors of product reliability. However, the rate is the key element here.

By controlling the rate we can reduce the damaging effect of thermal cycling manifold - also exponentially. Therefore it is always important to understand how the product handles the changes of its state. In our particular case the tubes heat up very gradually, so the rate of temperature change is substantially reduced.

All this would of course be academic without hard experience, and that experience tells us that we do not see tubes die catastrophically after 10 or 15 years, as the rule. And damage due to thermal cycling tend to manifest itself as catastrophic failure.

What we normally see is slow deterioration of tubes, most likely due to the depletion of their cathodes. Meaning - long operating hours.

As there is no simple answer, every user has to develop his own way of operating the components - we just give him the tools. All I am trying to express here is the fact that no single universal truth exists in that regard.

Regards,

Victor

09-01-10: Maril555
I've had BAT REX in my system for a significant period of time, and so far, it's the best preamp I've ever heard (others include Supratek, Nagra, Doshi).

I have considered those three preamps, too. Could you please describe how the Rex's musical presentation differed from them and others you've had the good fortune to use?

As usual, this thread deviated from the original question- comparison of BAT REX and Atma Sphere MP-1 (MK III?).

In this particular case, I find the discussions of tube life and 24/7 operation, while tangential to the original post, extremely relevant since both preamplifiers use 18 tubes each. I have read about amps/preamps who require retubing every couple of years at fairly high expense and would like to avoid that.

Again with apologies to those who are bothered by this tangent, I think we are actually saying much the same thing, Mr. Khomenko. I have or had mentioned in this thread and/or others that:

(i) operating voltage helps determine tube life, i.e., the more voltage a tube sees, the hotter it runs, and the quicker it will normally die; and

(ii) in order to avoid the sudden, deleterious application of voltage to tubes upon start up, some tube equipment - including your products, I am now learning - features a "soft-start" function that brings up power gradually.

Since we're on the topic and your Rex preamp features tube rectification, I should mention that tube rectification functions like a variac to bring up power gradually.

Not to belabor the point, but based upon the evidence I have seen, GENERALLY speaking, if the small-signal tubes in a given circuit are run at reasonable voltages (i.e., well below their maximum rating and they thus run cool) and the piece uses solid-state rectification without a soft-start or standby feature, which is the case, in my experience, with most tube preamps, 24/7 operation yields better tube life (and better sound). I again quote from the owner's manual of my VAC Renaissance tube amp:

"How long should tubes last? It has long been known in professional circles (and probably now forgotten) that a tube such as the 12AX7 will display BETTER performance characteristics after TWO YEARS of CONTINUAL operation than when it was new. In normal use it is not unusual for a low level [small-signal] tube to last 5 years or longer. Output tubes [i.e., power tubes used in tube power amps] are another story, as they are continuously providing significant amounts of current." (Emphasis original).

Incidentally, if, because of work demands, I know that I'm not going to be listening to my system during a period of a month or more (a common scenario for me at year-end), I will indeed t