Should I turn off tube (pre)amp after listenings, or keep powered up?

Basically, what is the better policy for extending the life of preamp tubes? What wears 'em out quicker: switching on and off, or just leaving 'em on?

I just got my first piece of tube hifi kit (a Croft integrated) that runs 3 12ax7s in the preamp stage; I've received conflicting advice re: operation of same.

 

Turning your tube gear on & off once or twice a day won't shorten the tubes' life nearly as quickly as leaving the equip. on all day, or leaving it on all day + all night.

 

If you have really cheap 12AX7's in there I wouldn't worry either way.
Figure, if they give up the ghost just replace them.
I wouldn't be concerned unless you have uber-expensive NOS tubes in
there that you want to preserve as much as possible..

 

I have been thinking about this question for just about my whole life. My father built a Dynaco tube preamp and amp in the early 60s, and he left the tops off with Whisper Fans blowing across them whenever on. His original tubes are still in good condition, both the amp and preamp, after more than 50 years and consistent use at least twice a week.

Now that I own my own tube equipment, I don't want the distraction of fans blowing. What I do is have my fans plugged into a dedicated remote control power outlet (from Radio Shack). Whenever I step away, the fans go on to cool the tubes.

But I DO NOT turn off tube equipment unless I will be away for more than 3 hours. I do believe power in-rush shortens tube life more than leaving on for some amount of time... I have never found a good answer to what that time is. So, I say... tube equipment doesn't sound its best until its been on for at least an hour, maybe as long as 8 hours. Therefore DO NOT turn it off if you are planning to come back soon, so that you can enjoy the equipment's best sound when you get back to listening. I randomly chose 3 hours as my limit.

Does everyone here agree that tube equipment suddenly gets REALLY good at some number of hours after it is turned on? And, supposedly, transistor equipment doesn't fully "warm-up" until days after it is turned-on.

 

Some electronics have "soft start" that brings tubes up gradually.
This might help with "power in-rush".

Again though, if you have three cheap 12AX7's is it really a concern?
Rare vintage tubes are a different story.

 

I am a gentleman of limited means.

 

I see from your profile that you are 114 years old.
I think regardless of whether you turn your pre amp off or not, the tubes will unfortunately most likely outlast you.

 

As will my Victrola. [sigh]

That was a cruel thrust, sir.

 

Enjoy the Croft.

 

Just my opinion here, perhaps you will get a consensus on this.
The tube electronics should be shut down, both to preserve the tubes and to conserve electricity.
However, if you intend to listen two or three or more times a day perhaps it would be
better left on to avoid excessive start ups which can be detrimental to the tubes.
I don't know if the Croft has soft start or not, if so this would be less of a concern.

 

It has a feature when you power it up - the LED above the power switch is red; after a minute or so, it turns green and you can start playing music. Could that be soft start?

 

Do you really have to worry about the life of a 12AX7 tube? I have had power tubes blow on me all the time, but I have never had a 12AX7 go out on me.

 

I am. Interesting piece of kit; it's plainly not engineered for antiseptically low distortion, 3D soundstage, etc.; yet, it's a compelling listen.

 

Another log on the fire: http://searsound.com/pdf/leaveiton.pdf
Searsound runs a lot of vintage studio gear of the highest order.

I warm up my gear for at least 1.5 hours before I listen. If I am listening throughout the day, I leave it on. But, the only piece of tube gear I left on all the time was my Lamm (Reference) line stage, and that, only because the manufacturer advised it (and it took days to come back on song- solid state audio path and tube power supply).

 

Contact Glenn Croft . Myself I would switch off.

 

Tubes are JJ Audio, of Slovakia apparently; anybody know anything about them?

 

I'm going to leave the Croft on overnight as an experiment. I've only had the amp for a day now; my first tube experience (apart from guitar amps). Art Dudley thought that the initial graininess went away after two days (something I'm not hearing, or don't think I'm hearing).

 

This is solid advice in my experience (and Warren has far more than I).
I usually come home, turn on my amp and start listening after puttering about for 45 mins or so.
I find that the system really sings after a few hours (let's say two hours), and just gets better and better with every LP after that.
I usually listen for three or four hours, but then I'm off to bed and not listening again until the following evening, so I always power down the system when I hit the sheets.

 

If I know I'm listening more that day, I'll leave it on... But never over night or extended periods.

I do try not to turn it off and on... Why? not sure.

 

Hahahahaha!

 

Not absolutely sure but I think these are decent quality tubes (about $10 each), maybe not as 'refined' as some, but good solid tubes. At some point if you can, get some Genalex Gold Lions (about $45 each for the premium gold pin version - get these), they are almost universally praised for their sound quality. To me, the GLs sounded as good or better (altho very much in the same 'family' sonically) than some used but tested good 1970s vintage Telefunken ribbed plates in a McIntosh C220 preamp. The GLs may be more musical than the JJs, but it is going to be rather subtle, depending on your sensitivity and listening tastes. You MAY even get a little more 3D space using the better tubes ...?

Yes, I think the delay/LED indicates it has a soft start (or Croft thinks it only takes 1 minute from cold to sound good!).

BTW, I'd turn the amp off if you won't be listening to it for a couple hours. If the 12AX7s are the only tubes in it, yes, they'll likely not burn out, but unless Croft recommends it, I don't think there's a reason to leave it on 24/7. Try it a couple times and see (leave on overnight, listen, then turn off overnight and listen 'cold' and again after 1 hour, 2 hours ...).

Edit/PS: I see that 2 of the 12AX7s are for the phono stage, 1 is used as a (dual) driver for the output MOSFETs. I'd try a single Gold Lion in the 'driver' position (hopefully one can determine which tube that is!) and see if you notice a sonic difference. It may take several hours to 'settle in' after changing. Also, I wouldn't change anything until running the amp for a month or more, IT will take some time to settle in too (unless you don't "believe" in such things!).

Hopefully you use or will use the phono stage, having a nice tubed phono stage is a good thing. If finances are particularly tight, you can likely wait a while before trying new phono tubes.

OF COURSE there are 100s of variations of tubes to try. If you like more lush sonics, possibly Mullards would float your boat, etc., etc. ...

Merry Christmas!

 

.
http://forums.stevehoffman.tv/threads/leave-tubes-on-all-the-time.394223/

 

Glenn Croft himself (a very nice man!) emailed me and said turn it off when not in use. And, I shall. Whenever that happens ....

 

Had JJ Tubes, sound good but QC issues. Suggest NOT using their power tubes, when the go, they are known to take components with them. I was forewarned about this as I had two sets that came new with my Rogue M-120 monoblocks that I had purchased used off of eBay. As I was going to upgrade the amp after these tubes died, it wasn't an issue. When they die, they die hard and did indeed take out components. I have my new M-150's and to be sure, they will never see JJ's.