What's likely to happen when an 845 tube fails?


I've been running tube gear as far back as I can remember and other than a CJ mono amp blowing a 6550 and requiring factory service many years ago, I've never had any serious issues. Sure, tubes age and you eventually replace them or on a rare occasion, a tube blows, maybe you replace a fuse, then you're back up and running, but that's been it.

Atma-Sphere MA-1 monos and MP-1 pre currently hold pride of place and I'm also very fond of a Cary SLI-80 F1 all triode that I run in another system. But... I've been itching to try a pair of deHavilland Aries 845-G SET monos and am wondering how much grief those big, high voltage 845's might cause me?

In the case of "catastrophic failure", is it likely to do serious damage to the amp? Worse yet, how 'bout my speakers? Any comments from those having personal experience with 845's or 211's would be appreciated.

Regards!
128x128rfogel8
Phil, now that's the kind of useful info I was looking for!!! Thanks for taking the time and being so thorough.

Joe/Trelja, thanks too for your comments. You and I discussed the merits of the 845 a while back and I'm still dragging my feet. I know it's not your favorite choice for SET but the only other amps that peak my interest are the Wavelength Cardinal's. I'm fearful the 300B will fall a bit short on power and probably be a little "soft" compared to the 845. Yah, I know, many feel the 300B has a more interesting sound.

Decisions, decisions.
There's nothing about a 300B that gives it an intrinsically "more interesting sound" than an 845. The differences are in execution more than the tube itself, though there are some characteristics that correspond to the power tube chosen. If you doubt this, get a 300B amp and then listen to Chinese solid plate, mesh plate, Sophia, Shuguang or TJ high-metallurgy, KR Audio, EAT, JJ and Russian 300B variants in it, and you'll hear that it's not the 300B that makes a 300B amp "interesting."

But look, they're both triodes, and applied single-ended, they will sound far more similar than either tube will to a push-pull implementation, or to a single-ended tetrode or pentode amp, using KT88 or EL34, respectively.

I have Audion Black Shadow 845 SET monoblocks on one system and Audion Golden Dream 300B PSET monoblocks on another. Sometimes I change which system each pair is in. The two amp types have the same power rating, but the 845 have more drive; the 300B have a little more finesse. But we're talking degrees. The 300B PSET amps have more silver in them (wiring + transformer secondaries). Both are solid state rectified. The input sections are similar; the driver tubes are the most different element.

I have had a number of very good 300B SET (not PSET) amps, and have had numerous 2a3, 45 and 6c33c SE amps come through my systems. The Audion 845, and I'll also say Sophia 845s had finesse and tonal density competitive with other makers' 300B and lower power SET amps. As well, most 300B amps have had too little discipline in the deep bass region to be usable on truly full-range speakers. I'll go further to say that to 70% of everyone who has heard both 300B and 845 amps on my main system, the 845 amps have the "more interesting sound," because of their dynamic energy and overall more vigorous drive.

There are many very fine 300B SET amps, including Audion's own, Coincident and Wavelength, but even on highly-efficient speakers, there is intrinsic value to the power and drive of a well-designed 845, for transient dynamic clarity that doesn't sacrifice agility, transparency, speed and finesse. Yes, equally well-designed 300B and 845 SET amps usually sound somewhat different from one another, but which one is "more interesting," will depend on what you value sonically, on a polar graph of imperfection.

If you have clarity, musical realism, speed and convincing tonal completeness from an 845, as well as same from a 300B SET running only 1/3 - 1/4 the power, the dynamic factors of having the 845's reserve and punch will show differentiating value even if you listen at moderate volumes. And to get the same power and clarity from 300B PSET will generally be more expensive to produce with all other factors in league or better. So don't discount a good 845 alternative on rumours of 300B SET being "more interesting."

My 300B PSET amps are among the 3-5 best power amplifiers I've ever heard at any price. They cost 50% more than my same-power 845 SET amps and they also better any 300B SET amp I've heard. My 845 amps are also in that class of 3-5 best amps so far. My 300B PSET amps couldn't be built and offered to the same retail price.

I like both; I have both. But if I could only have one, I'd have the 845 for being more versatile, more convincing in a wider variety of circumstances because of the 845's more robust dynamic behavior and it's better deep bass discipline. Other factors are fully competitive. In the context of having the 845 already, then the 300B PSET are appreciated for their more intricate finesse, though unmistakably at some comparative loss of drive.

Either tube can reside in a poorly designed and executed circuit that negates all of this.

Phil
I'm not sure, but I've heard it from reliable sources that a bad 845 will explode, showering the room with glass and poison gas and killing everyone within a 3 mile radius. But that's a risk I'm willing to take.
Phil, Thanks again for your excellent input. Many of the points you make, I've either heard or read before so I was already thinking along the same lines. All things being fairly equal, the extra power of an 845 seems preferable to the alternatives and certainly provides more flexibility.

Chayro, thanks too for your comments. I'll make sure to wear a protection suit when I'm listening!
213cobra, "most 300B amps have had too little discipline in the deep bass region to be usable on truly full-range speakers."

Although someone here recently disagreed vehemently with me on this point, I agree with Phil's comment.

Also, I might have heard the same 845 amp Phil uses at a Zu get together two months ago here on the East Coast, though I'm not sure.

Bob, I've been around the DeHavilland 845 monos you're considering, both at the local dealer who had it on display, and at the customer (our own Sbank) who wound up purchasing it. They're quite a competent, and I believe, well-engineered pair of amplifiers.

That said, I'm going to guess the amplifier is going to be used in powering your Fried C3/L-C4 satellites. Is that right or wrong? If it is those speakers, as we've discussed many times, you don't need very much at all to drive them, and low end isn't a concern in this instance. After yesterday, where I was at an old tube amplifier builder friend's workshop, and we drove an old pair of Dynaco A25 with a 2 wpc 45 SET amp, I'm more convinced about the Fried's requirements than I was before that. No matter what you go with, the Frieds will be more than fine.