2. amps-preamps
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Is it OK to leave a tube preamp on all the time?

I just recently purchased a used VTL 2.5 preamp that I'm using along side with an Adcom home theater processor. I've had to do this because I can't find a processor under $2500 that keeps me happy for two channel music. I'm currently going from the Adcom processor front pre outs, to the processor input on the VTL, then out to the amp inputs. I connect only my CD player and turntable to the VTL, and all video sources to the Adcom.

My wife has become very frustrated with this arrangement because it's much too complicated to figure out what to turn on and off, and which volume to adjust- so I've had to constantly leave the unit on and turn until the volume so it's balanced with the centers and rears. Does anyone know if leaving on constantly (but without passing any signal through) shortens the tube life? The logical answer would be yes, but I'd like to know for sure. Or is there another way that I can feed both the VTL preamp and my processor to the amp input without losing sonic quality (like a very high quality Y connector)?

Any advice would be appreciated. I know the easy answer is to get rid of the wife, but that's not an option right now ;)

Thanks!
alouie
karls
332 posts
 
Small-signal tubes are usually rated for about a 10,000 hour lifespan, give or take. They will often last a lot longer, but they start to get noisier and sonic quality does start to degrade. So if you leave your preamp on 24/7, 10,000 hours is reached in a little over a year. If you are willing to retube your preamp every year, then no problem. Otherwise, turn it off when not playing, and you'll probably get 10 years or more of tube life. Power amps are even worse, with output tube life of a few thousand hours and much higher replacement costs.
glen's avatar
glen
714 posts
 
I have a question. Do you guys turn your stuff on and let it sit for the warm up period before passing a signal through it?

It seems to me that waiting an hour for an amp to warm up is a bit extreme.

I guess what I'm really asking is will it harm the Amp/pre-amp to start listening to music while the tubes are still cold/unstable?

Thanks in advance. I'm a little new to the tube game
sean
6,231 posts
 
If you put a signal through a tube before it reaches operating temperature, you will know it. It sounds HORRIBLE.

Having said that, once you turn on a tube set and the filaments begin to glow, you are ready to operate in well under one minute. Give it a minute just to be sure though. The sound might not be near as good as if you let it idle for a bit longer, but why waste time when you can be listening to tunes ? Try not to "throttle" stone cold tubes though, as this is when you are most likely to do damage to them. That or getting the plates cherry red by overdriving them or having a bias problem.

Keep in mind that this is a broad generalization. Some tube gear might have soft start or circuitry that delays the firing of tubes to minimize in-rush current. Read your manual and go from there. Sean
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mezmo
516 posts
 
Had a VTL TL 2.5 myself for about two years, and I pretty much left it on all the time except when I knew I was going to be away for a couple of days or more (and then I'd usually turn it off and unplug it). From all that I've heard from VTL and read about their gear, they seem to recommend such an approach. Now I've got a Rogue 99, and they've got a deliberate soft-start circuit to protect the tubes at power up and explicitly suggest that you turn the thing off when you're not using it in order to prolong tube life -- so that's what I do. Which is right? No idea. I've blindly deferred to the fellows who designed the stuff on this one.
marakanetz's avatar
marakanetz
5,473 posts
 
Glen, to answer your question -- certainly Yes you should leave your tube rig for at least an hour (especially if you have tubes on the front end) before you will pass the signal. You can clean vinyl or CDs or write bills or have a quality time before you will start listening:)
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