If tube amp is left on, but not playing........

Dear Mr. Ghost Rider,

I cannot disagree. Your point about thermal shock is very real. That is why light bulbs almost always burn out when first turned on.

I think it all depends on how much the equipment is used. If you play your amps only on the weekends, then it probably makes no sense to leave them on all the time. If you listen all day long every day then maybe you should leave them on all the time. I have never heard a definitive answer, but perhaps someone here can site a study that will tell us for sure.

I turn my amps off when I am not at home or I am sleeping. I am more worried about fire than consumption of electricity or tubes though.

To Herman:

I hold an Amateur Radio license (though inactive now), and back in the late 60's early 70's just about all amateur gear was tube. The bigest cause of tube failure was considered to be thermal cycling caused by turn on/turn off cycles. Many hams kept filament voltage on to keep the temparature stabilized and just turned on B+ for operation. It seemed to work.

Hi GS556, I am afraid you are wrong on all counts. A transistor and a tube operate in the same fashion when used in an audio circuit. It is true that a transistor will be off with no signal or bias applied to the base, and a tube will be on with no signal or bias applied to the grid, but they are never used in an audio circuit without some bias applied.

How much current they pass at certain signal levels depends on how they are configured. Class AB push-pull amps, whether tube or transistor, pass a small amount of current at idle and more when a signal is applied. Class A amps, whether tube or transistor, pass approximately half of the maximum current at idle and then this amount varies up and down with the applied signal.

The reason you should never power up a tube amp with no speakers hooked up has to do with how the output transformer operates, not how the tube operates. Energy is transferred from the primary of the transformer to the secondary by magnetic fields. When the expanding and contracting magnetic fields created by currents in the primary windings cut through the secondary windings, they induce current to flow through the speaker. Without a speaker hooked up, this energy has no where to go but back through the transformer primary where it induces a large voltage across the output tubes. This can cause the tubes to arc and damage them.

"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

Well IMO the tube still radiates electrons due to the boiling off process. Tubes send electrons across vacuum space and with music, much much more, without music, just less of them, but still a 'rush of white noise'- turn up the volume to hear it. Turn the unit off to save tubes is my suggestion. At the top is a tube that is still in the box..next is a tube on but not playing music...bottom is a tube that plays music... this is in life hours IMO.

LMAO @ Tom, a NOS 300b tube no doubt!

You might consider a hybrid amp like a Blue Circle or Llano.

Just tell your wife how much the 300b tubes cost, and she will never again leave it on (assuming she lets you keep it)!

Tom

Just tell your wife how much the 300b tubes cost, and she will never again leave it on (assuming she lets you keep it)!

Tom

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 think turning off B+ will help much if the filament is on. The filament will still be cooking away and shortening the life of the tube.

Yes, the amp will still put "burn time" on the tubes.

I have always seen that wives think that YOU are the one who is supposed to be trained, or change YOUR behavior.

Happy New Year, Mythtrip!

An SET runs Class A (by definition!), and tubes in Class A designs pass plate current equal to rated power output at idle, so you should expect a significant impact on tube life.

What you want is a tube amp with the option to turn off just the B+ voltage, leaving the filaments on.

In my experience wives are not trainable....