is it better to leave a tubed preamp powered up 24/7 or turn it off after each use

[W WALDECKER]

is tube life prolonged or diminished by leaving the preamp running 24/7? i have heard differing opinions on this and hoped someone with a good knowledge of tubes in general could elaborate and shine some light on this subject..................thanks................... WCW III

[ward91]

I thought tubes got hot and in the book it tells you to turn them off ?(so I’ve heard)

[RuSsMaN]

Turn it off.

Your standard 6 and 12 volt front end tubes, 6DJ8, 12AU/AT/AX7 have a life span of approx 10,000 hours, +/- 2000, depending on the design.

Higher gain front end tubes, ala 6SN7 / 6SL7 should go 8000 or so.

After burn in, you reach optimal operating potetional after 3-5 minutes from power on.

Cheers,
Russ

[madmax]

Leave it on.

I've never actually had a tube die because of age so I am referring mostly to what I've read on the subject. I've read a lot in various places so I have no clue where exactly to point you so I'll just rattle off some different takes on it.

Most say the average tube life you can expect is 3000 hours. That is 125 days. My preamp has been on for about the past three years. That is 26280 hours. Some say they are more likely to die at powerup like a lightbulb. Anyone ever see a lightbulb that died other than when you turned it on? Maybe, but most often it is at turn on. Add to all this confusion that some tubes die very early and others (of the same type and construction) last for quite a long time.

Personally, I leave mine on because it takes about 3 days before they sound consistant all the time. Have you ever run into your sound being glorious one day and suck the next? Mine used to do that all the time and I always figured it was my state of mind, fluctuating voltages or something. Magically, this went away after leaving the preamp on all the time.

madmax

Edit: just read russmans post. I'll agree to the 10K hours or whatever it was rather than the 3K hours I listed. This may be a number for power tubes, not preamp tubes. I pretty much have a very different opinion otherwise though. :)

[RuSsMaN]

The lightbulb analogy doesn't really work. Most, yes MOST tube preamps have a soft-start, or timer chip to let plate voltage stabalize, before full B+, which isn't much for line amp tubes anyway. A light bulb is directly wired in the path of the current. No power transformers, no caps, no bias resistors, no 'protection'.

I'm biased (pun), I live in Tornado Alley. So my vote for off is also influenced by what mother nature likes to do around this neck of the woods.

;)

[dorokusai]

I also vote "OFF". I have noticed no difference in the performance of my gear after being on for more than 24 hours; however I definetly let my gear warm up for about an hour before getting naked.

[RuSsMaN]

Oh, and the hour quote is running the tube at its full potential, right on the ragged edge. I'm not suprised you've gotten 20K+.

Cheers,
Russ

[Dennis Gardner]

I vote turn it off, but don't let those Odysseys power down.....................you know how long it takes for them to level back out...............but I know you already knew that. ;)

[ward91]

What does the manual say??

[madmax]

The lightbulb analogy doesn't really work. Most, yes MOST tube preamps have a soft-start, or timer chip to let plate voltage stabalize, before full B+, which isn't much for line amp tubes anyway. A light bulb is directly wired in the path of the current. No power transformers, no caps, no bias resistors, no 'protection'.

;)

The filament (sp) is what I read as comparing to the light bulb. Ever watch a telefunken preamp tube power up? Flash!


madmax

[RuSsMaN]

Never seen a tube flash. Including all the Scott and Fisher integrateds I have (dozens)with Smooth and Ribbed plate TF's on the front end.

If a tube is flashing on power up, you've got some resistors out of spec.

Cheers,
Russ

[madmax]

Flashing.

http://www.tabcrawler.com/articles.p...e&articleid=78

Have you ever noticed how some tubes like new old stock Mullard or Amperex 12AX7s "flash" brightly when you turn on the power? The answer is rather technical so bear with me. The two filaments have unequal cold resistances. When power is first applied, the filament with the lower resistance passes more voltage over to the other filament, which makes it glow brightly (Ohm's Law at work). As the lower voltage filament warms up, its resistance rises to the hot resistance of the other filament, allowing both to get equal voltages. This effect is pronounced in amplifiers with AC filament supplies because larger amounts of current are available for the tubes, DC filament supplies light those found in better hi-fi equipment tend to be current limited, reducing the opportunity to "flash."

madmax

Edit: Of course, according to the article I guess the manleys and jolidas must not be "better hifi equipment". :D

[BlueMDPicker]

From my experience, with 12AX7 and 12AT7 tubes in my gear (none of which has out of tolerance components), Amperex tubes (made in Holland) consistently flash when the filament is first energized. Other tubes that do this are Mullard (UK), Matsu****a (in guitar amp and stereo gear) and the Yugo Ei's.

More to the subject, I don't leave any tube gear running continuosly. As Mark stated, I've found a good warm-up period before listening eliminates any perceived inconsistencies between listening sessions (for these vintage ears.) Having said that, I must also note that madmax has rather remarkable hearing -- so, I'm willing to defer to his opinion if you happen to be equally blessed.

[RuSsMaN]

Odd, never seen anything flash, other that a power tube with biasing issues.

I'll see what the Anthem does, with some Mullard and Amperex 83's. Interesting. My instant reaction would be 'turn it off, turn it off!!!'.

Cheers,
Russ

[BlueMDPicker]

The Mullard CV4024's will leave a skid mark in your shorts if you're not prepared for the flash. They are the hands down best front end for my Manley 75+75, but they caught me flat-footed the first time.

[Emlyn]

I would always turn my Anthem Pre-2L or 2L SE off if they weren't going to be used for more than a couple of hours, but only because they had no standby mode. It would take a few minutes for them to start sounding really good once turned on. If they were turned on though, they were left on for at least a couple of hours rather than cycling them on and off in short intervals. I would suggest you could leave an Anthem preamp on continuously and expect to get at least a couple of years of life out of a set of (4?) tubes. But to do so doesn't have any performance benefit other than not having to wait several minutes for warmup.

The Sonic Frontiers Line products have a standby mode, so I just use that instead of leaving the preamps on or turning them off at the power supply. Apparently, it's supposed to take up to three days for the preamp to stabilize if the main power supply is turned off. They require no warmup period if they are left in standby with a small amount of current going to the tubes. I was a little concerned about the potential expense of replacing tubes in the Line preamp, but that's turned out to be of little concern now. Apparently, Sonic Frontiers designed their last preamp products to run the tubes at way below the maximum ratings for the tubes. The stock Sovtek tubes in my first Line 3 have been used for 5 years without need for any replacement. They're cheap, and only two of the ten 6DJ8 type tubes really matter to signal quality anyway.

The mini tubes in the Musical Fidelity line buffer, which I guess is a preamp in a way, are supposed to be rated for 100,000 hours (more than 11 years) and put out hardly any heat or use much power, so that stays on all the time.

[madmax]

The Mullard CV4024's will leave a skid mark in your shorts if you're not prepared for the flash.

Ha Ha, I have those same skid marks after my first time! Russman said "turn it off, turn it off" but at the time I was thinking more "I ain't touching it" and looked for the power cord. Quite exciting the first time.

madmax

[organ]

Wow excellent thread. Once I turn my pre amp on, it doesn't go off unless I have to leave the house or before going to bed. If I'm going to be home for 5 days straight, I leave it on for 5 days.

But it's a different story when it comes to power amps. Also, I bias my output tubes a little lower for long life. I've been using a pair of EL34EH for about a year and a half and it's still going strong.

I've had tubes that flash upon turn on. Ei X7, Mullard U7 and RFT U7.

Russ,
Do you know if my ASL pre run the tubes hard? It's pretty much the same as the Radii you had. I still love this pre. Just got it back last week from the tech and I forgot how good it sounds.

Maurice

[HBombToo]

I believe by power cycling a tube the enclosure suffers tremendous stresses. By leaving a tube powered up the enclosure reaches a thermal equilibrium which can increase the tube life. In the case of rectification tubes I do believe that their life will be decreased more so than amp tubes by leaving them on but the benefits to the enclosure are far greater.

That said, it is dangerouse to leave any electonics on during storms if there tubes or ss so pick your poison...

HBomb

[RuSsMaN]

I used the Radii for a couple years, never replaced a tube (after I rolled several, to find what I liked).