2. amps-preamps
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If tube amp is left on, but not playing........

If a tube amp is left on , but not playing, is the tube still wearing out? If you think of the tube as a valve, and no electrons are moving through it, it would seem that there is little to no wear on the tube. This is a significant question for me, I am considering a SET for a system that will be used by my family. My wife has never shut off a light in her lifetime, and will not turn off the amp when not in use. (Those of you who respond with suggestions on how to change my wife's behavior have never been married!!) thank you......Mark
mythtrip

Showing 1 response by upscaleaudio

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upscaleaudio
259 posts
 
"A tube burns out quicker with no signal. Tubes work in the opposite of transistors - a transistor will pass maximum current at the highest signal voltage and the least current at no signal. A tube will pass maximum current at no signal voltage and the lowest current at the highest voltage signal. And, BTW, this is why tube amps should never ever be powered on unless the speakers are connected."

I don't know what you mean by that...but

Negative bias voltage is applied to the grid of the tube. As you reduce this voltage, the plate current goes up. And the tube runs hotter.

So you can run a tube near cut-off by raising the amount of negative bias. This tube will certainly last longer than one that is

(a) Biased hotter

(b) Run at consistent high levels

So for new guys, when you read the bias meter and you go from 50mA up to 60mA, the "idle" goes up.

You are reducing the bias voltage which keeps the tube "in check" and running the tube hotter and by some (small) degree shortening life.

Getting back to the original question.

Don't leave your all tube power amps on all the time. But don't cycle them on/off several tmes a day either.

check this page for stuff that may be helpful

http://www.upscaleaudio.com/rare/basics.htm
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