leaving on a tube amp for long periods of time

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leaving on a tube amp for long periods of time

Post by biographers » Fri Sep 01, 2006 7:10 pm

Just a quick question-

I have a Fender Bassman Ten from the mid 70's and I'm wondering if it's wearing down my tubes by leaving the amp on for long periods of time when I'm not playing it. For example, if I play it leave it on for three hours but I'm really only playing it for one of those hours, is it better to turn it off and on several times or just leave it running? I know that turning it off and on a lot of times isn't the best thing for the amp either.

I know that at shows sometimes they let the amps warm up for a good hour before playing, but maybe that is a special case since they are driving them much harder and louder than I do when recording.

Thanks for any input.

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Post by 2121TrumbullAve » Sat Sep 02, 2006 12:29 am

I'm of the theory that electronic gear has a longer lifespan if it's left on for extended periods. Constant hot/cold transitions might be more harmful than consistent hot.

In a 30 year old amp like the one in question, I'd worry more about other parts of the circuit failing and not the tubes, which can be replaced easily and cheaply.

Use your standby switch and leave her on, I say.
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Post by Scodiddly » Sat Sep 02, 2006 1:00 pm

Leaving an amp on is fine, though it does suck electricity and create heat - not really what you want during a hot summer.

The deal with leaving amps on before a concert is really just to avoid problems. The amp is turned on before sound check, and just left on until the end of the show. If you turn it off, it might not turn back on before the show - power screwups, the power switch was on its last legs, etc.

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Post by hammertime » Sat Sep 02, 2006 4:56 pm

I left my McIntosh tube stereo amp on (uses 6L6's if i recall) for a couple of months once. Still worked fine. As long as you don't have the gain cranked up it shouldn't matter. What really fucks them up is turning them on and off, and of course, turning the amp up to 10.

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Post by drumsound » Sun Sep 03, 2006 10:37 am

You talking about a few hours here. That's no big deal. I like the amps to be on for a while before recording. Actually I like all the gear to be on for a while before recording. I hardly ever turn off my console. Usually when I start a multi day project the tape deck stays on the whole time, and sometimes the outboard too.

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Post by bocmaxima » Sun Sep 03, 2006 11:05 am

I have an Orange head, and I leave it on for long periods of time and never had a problem. Actually, I prefer my head to have warmed up about 30 minutes before I record with it. I agree with drumsound about having the recording gear on for a while. Even when I'm at home with my 4track and small pre, I like the electricity coursing through it for a while before hand. Maybe its mental, but everything feels better.
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Post by vvv » Thu Sep 07, 2006 9:20 am

The only problems I have with leaving amps on is that

a. they must be cooled, either in a room with decent circulation, or with a fan (all of my bigger amps {50 watts+} have mini-fans installed, which can be switched off for recording), etc., and;

b. I don't like to leave them on if no one is present, just due to paranoia about fire...

Also, do remember to take them off of standby before you shut off the power.
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Post by jmoose » Thu Sep 07, 2006 10:11 am

I always let tube gear warm up for at least a 1/2 hour before doing anything, usually it's more like an hour. The first thing I do is flip on the lava lamps, then the tube gear, then make some coffee.

When the lava's flowin' the tubes are glowin' which means its time to get to work!

I wouldn't be too worried about it. One time I left a Boogie on all night...it was fine.
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Post by newguy12 » Thu Sep 07, 2006 2:15 pm

vvv wrote: Also, do remember to take them off of standby before you shut off the power.
I thought you turned them on and off with standby on. In fact, I thought you were supposed to turn it on with standby, let it sit for a minute or so before taking it off standby and then when you wanted to turn it off you would do the reverse, put it on standby, give it a minute and then turn it off.

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Post by jmoose » Thu Sep 07, 2006 3:02 pm

I always let 'em warm up on standby for at least 4-5 minutes...that allows plenty of time for the voltage to stabilize.

Some amps, I've known more then a FEW old Marshalls and such that like to sit on standby for like 10-15 minutes otherwise they get all cranky.
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Post by ivanovich » Fri Sep 08, 2006 8:57 am

the tech that repairs and maintains my tube gear tells me that the equipment (ampex tape deck and electronics) could be left ON 24/7 with an occasional rest. i told him that i would never leave it 24/7 because i'm not in a pro studio situation, i only use the deck n stuff when i need to. he said it might be a good idea to get a Variac transformer (he found one for me) so that i could warm them up slowly.....30-60-90-117volts..... and if i'm doing a long session (weekly-monthly)to just leave them on but cut back on the voltage when not in use. keep in mind that most of these electronics are over 50 years old....

it was my understanding however that tubes are ready to go like 10-30 seconds after they're turned on though. i'm not to sure about it.


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Post by UXB » Fri Sep 08, 2006 9:38 am

It's my understanding that my class A amp will chew its tubes up very quickly if left in the "on" position and not on standby, but once on standby...hmmmm.

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Post by Professor T » Fri Sep 08, 2006 9:38 am

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Post by Brian » Sun Sep 10, 2006 5:20 pm

The way to go is "don't sweat it". If you turn it on make sure it has time to "warm up" before use like your board it needs to reach a stable temperature, hence the term "warm sound" = warmed up equipment. Your digital word clock's crystals need to reach a stable temp to reah a stable size = dimensional stability = a steady clock = lower jitter.
When your gear warms up you get a more reliably steady tone so when you dub it doesn't sound like it. I leave my stuff on for extremely long periods of time. I left my marshall on for about six months once, no problems, tubes lasted 10 years. I need new tubes now though. Thanks for reminding me.

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Post by spacelabstudio » Mon Sep 11, 2006 9:03 am

One things that nobody's mentioned is tubes seem to need some time to burn off impurities. At least that's how it was explained to me. I imagine in some older tubes with a near, but not quite perfect vacuum seal, the occasional stray molecule gets in the vacuum and messes things up. Leaving it on for a while burns these off and gets you back to quiet operation.

Notwithstanding my half assed physical explanation, how I've seen this manifested in practical terms is tubes will sometimes when you first crank them up put a lot of noise and wooshy random waves of static. If you just leave them on for a while, anywhere from 10 minutes to a few hours, it will go away. I've mostly only seen this with old tubes that probably needed replacing anyway, but a lot of old tube mics use esoteric and expensive tubes that aren't easy to replace, and there's always the fear of spoiling the juju of that mic. Some studios leave their tube mics on all the time, for this reason. Others just make sure that they're on the night before a session. I saw a producer get really made one time because an assistant had gone around and unplugged everything the night before and plugged it back in in the morning, and his tube mic was popping like crazy and unusable as a result.

Anyway, not all tubes do this. I have a several tube guitar amps and one tube microphone, and the only time this has happened to me recently is with a tube mic I turned on only 30 minutes prior to the session that was noisy as all get out. About an hour in to the session it suddenly got very quiet and well behaved. It's a new mic built probably with a NOS tube, and maybe it has a tiny, tiny leak somewhere that lets in a few air molecules. Occasionally I'll get a little noise an a guitar amp, but generally don't, and letting it warm up for a bit always fixes the problem.


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