NOS tube paranoia!

I'm hoping to gain a little perceptive on the subject of tubes and their life expectancy.

I've got a Manley Labs Chinook tube phono pre with some relatively expensive NOS tubes plugged in. Because I want to preserve the life of these beauties as long as possible, I find myself not turning it on for a quick listening session like I did when I had a SS tube pre and I feel like I'm not enjoying it as much as I should.

I read some where from a respected tube guy that turning your pre on and off quickly is the quickest way to degrade the life of our tubes.

How do you folks deal with your tube preamps?

-Mike

 

Ahhhh... the tube aficionado's dilemma. Vintage tubes can certainly improve your gears's sound but at what price and for how long?! Sourcing decent tubes is getting much more difficult and prices keep rising with the market. There was a time when folks bought sheaths or even full boxes of nice tubes but you rarely see such quantities these days and back then, I knew fellas that left their tube gear on 24/7 because they couldn't be bothered with waiting 30min to an hour for their system to sound 'right'. I don't hear such arguments anymore.

So, what to do... Luckily, you are using dual triodes in the Chinook - 6DJ8, 6922, 7308, ECC88, CCa, etc. and these tend to be very long-lasting tubes (10,000 hrs and up). If you find a tube you particularly like, then buy 3 or 4 replacement sets and you're good for life (unless you keep the system running 24/7). Also, the tubes can serve as an investment and will help offset the cost should you decide to buy another phono pre. Vacuum tubes are old tech and its very rare to come across a modern tube that equals, much less exceeds the performance and quality of the old guards so I wouldn't wait around too long hoping for recent production tubes to catch up and if they do, I'd imagine that they would easily rival the 'Old Stock' in price.

As an aside, I have a Scott 222c integrated in a 2nd system and save for a brief stint at Terry DeWick's for a refurb and upgrades, its been used regularly in my house for the last 20+ years. It still has the original preamp tubes (Telefunken 12AX7) that were installed back in 1961 and they check out fine according to Terry and my tube tester (>85%). Of course, they could all fail tomorrow but I think I've gotten more than I could hope for with these tubes and I'd give 'em a decent sendoff...

 

You will probably have the longest life if you turn on your gear shortly before you plan to listen, and then turn it off before you go to bed. Basically the best rule is to leave it on for the remainder of the day if you plan to listen at all. If you don't plan to listen, then just don't turn it on that day.

I used to run my tube preamp 24/7, except when I was on vacation. But this generally gave me about 3-4 years of tube life before the preamp started to loose its magic. But now that the tubes which I really like cost over $100 each, I'm not doing that anymore!

 

Having a number of tube guitar amps I'm very glad I have not used tube audio gear since the 60's. To me, what works well in guitar amps for guitar music is not something that I want to carry over into my home audio gear.

 

Relax and just use it as you wish. What, you paid extra for an appliance that you are reluctant to use? No, you wanted the best sound that you could afford. So just turn it on when you want to listen and off when you are ready to retire for the evening. The only thing that really dings tube life is short intervals, like a minute or so, of use. That causes the tubes to go through temperature and voltage extremes in a short period and causes physical stress. Once a tube has heated up for an hour or so, it's fully stabilized and you can turn it back off as if it had been on for days. If you can't afford the occasional tube failure of $100+ tubes, then buy less expensive replacements.
-Bill

 

Thanks for the comments everyone. An extra set of tubes has already been ordered and I'm just gonna enjoy the damn thing damnit!

 

I agree with everything you said, with the exception of your last sentence. I have some equipment which simply does not satisfy me at all when I use lesser tubes. I actually try to use New stock tubes as much as possible. And for most applications, I can find combinations of new stock tubes which sound excellent, if I try hard enough to mix and match to achieve the right voicing. However in the case of the 6DJ8 class tubes, I only actually enjoy the sound of two or three particular old-stock tubes inside of my venerable SP8. Nothing else sounds right, including the vast majority of NOS tubes which I have tried. And I don't think that my SP8 is alone in this regard. Although this may just be because I have a very particular voicing in mind whenever I listen.

Unfortunately there are times like these where certain pieces of equipment simply aren't even worth listening to with lesser tubes IMO. And sometimes pieces are voiced so precisely to a particular tube that nothing else sounds right in there. So in these cases, you'd better be willing to spend the money, or you are never going to be happy with the sound of that unit.

But otherwise we are in complete agreement: If you have the equipment, you might as well use it. Its stupid just to let it sit. Its not like your hearing is going to improve as you get older!

 

NOS tubes are not necessarily better. Sometimes they are but the price is mostly driven by status and neurosis.

 

Except they are better about 99% of time and they are also much more reliable. Personally, I'm done with new tubes until they can turn out quality with consistency. New tubes offer much less value if they can't last half as long as NOS tubes, and they will last 50% as long only on rare occasions, usually their useful life is less than 50% of what it should be.

Pappas, you may die in a car crash tomorrow. Might as well turn on that system!

 

Well said Dave!

Sorry Burt. NOS were made at a time when manufacturing was so tight that military's 'round the world could depend on them. Tubes made these I'm not sure make the grade.

 

Since we're on the subject of tube life...

I'm planning on dropping some NOS Telefunken 7DJ8's into my Manley Chinook when it arrives. In trying to get my head around what type of life I might expect from these tubes, it seems I have run into some contradictions/competing theories:

From Galen Carol's site: "The PCC88/7DJ8 is virtually identical to the 6DJ8/6922, but has a slightly higher (7 volt) heater rating, which may suggest longer life."

From Audio Asylum (apparently quoted from Kevin Deal @ Upscale Audio): "Special note on the use of 7DJ8..is it O.K.? It will work just fine, but you may experience a shorter life from this tube. The reason? The standard test for the remaining life of a tube is to reduce the filament voltage by 10% and see how much the Gm meter of the tube tester droops. When you use a 7DJ8…you are already lowering your filament voltage by 10% when you put it in the amp…so where do you go from there? But if you get 'em cheap enough and you like 'em…have fun. "

Seems like I remember reading something from Brent Jesse awhile back that favored what Galen Carol said.

So...who is right?!?!

 

I bought four of them awhile back for an ARC LS-16, which were used sparingly before I sold the unit (with the stock tubes) and returned to a solid state preamp.

Since I have them here doing nothing, I figured they would probably be an upgrade over what is in the Chinook right now.

 

Just seemed odd that there were different opinions...I've not a clue, which is the only reason I asked. In the end, it's not that big of a deal, I was just curious if any other forum members had an opinion.

 

It's right on the edge of not enough heater voltage, so the cathode temps might be lower than ideal to loosen up those electrons fully. You'll only know by experimentation whether it matters or not. I wouldn't expect shorter tube life as a result, but noise could be an issue if the cathode isn't hot enough.

 

That depends on the tube. For instance, most 6h30 circuits won't see a substantial improvement from rolling in a spendy, old DR tube over any of the latest batches from one of New Sensor's brands. There's a similar story with fat 6ca7s.

Other tubes have different stories, obviously. Off the top of my head, I'm not sure anyone makes a 12at7 as well as Amperex did.

The biggest problem is really finding a consistent source of the old bottles. A GE 7044 is going to be better in most circuits than a 6h30, but the 7044 is deeply extinct. The predictability of new production has some real advantages. After all, everything sounds better when you're not worried that you're listening to it for the last time.

 

First off IMO NOS tubes no longer exist. There are lots of
'gently used old tubes' around for sale called NOS, but real NOS? I am laughing hard.
If the op cannot use the item for fear of using up the tubes.. Then he needs to stop owning a tubed device. Or buy new production tubes and stop worrying.

 

Well, you'd be wrong. I've got several large boxes of tubes that have "never" been used in anything. Lots of your typical 9-pin audio tubes, as well as octal power tubes, and some transmitter tubes etc. Many of these tubes would have been spares for military radios etc. And I'm not the only one with a stash of tubes. Of course, what's for sale on ebay could be anywhere from truly NOS, to almost dead.

jeff

 

The old tubes are often better, but there were crap tubes made back then as well, plus many NOS tubes have been stored under conditions that will degrade the cathode chemistry, or have been bouncing around in military vehicles for years. A lot of tubes were carried onboard as spares in certain military applications.

There are still a lot of MOST NOS types around-a few have become legitimately rare-but the problem is that huge surplus stocks were bought up by a few dealers and they are keeping the price high. Eventually they will be gone.

I have a lot of them myself and I have sold off a few to finance gear purchases (usually tools and test equipment). They still show up at hamfests and estate sales on occasion.

 

Some NOS tubes are noisy, like some of the NOS 6sl7's, so for these I need to be very picky if looking at NOS.

I don't think that NOS means better, in all cases.

 

There are NOS tubes out there-most types were made in huge quantities, in batches, and there are still millions in warehouses that come out on occasion. There's still WWII mil surplus of all types that comes out every once in a while, a recent warehouse demolition sale out here turned up a huge pile of P&W radial aircraft engine parts.

Getting them is the problem. The sharks have nothing better to do than going around and ferreting this stuff out.

Certainly, a lot of used tubes are sold dishonestly as NOS. Some are equipment pulls with little or no time on them, some have thousands of hours. 300Bs were used as voltage regulators in the Nike air defense system, for example. GE made an industrial control system that used something like 75 6L6GCs. These things turn up every once in a while and the sharks all know what they are.

So they're out there.

 

I agree that NOS is tossed around casually these days but real NOS ARE available
although usually expensive and the obvious price curve is up!