When to power off a tube amp?

Most tube gear sounds pretty decent within 10-15 minutes of being turned on so there is no good reason to leave the gear on all of the time--waste of energy and waste of the limited life of tubes. While there is a possible safety issue with leaving tube gear on unattended, the chances of a fire is extremely low, and such risk would apply to solid state gear as well.

Tubes are NOT like light bulbs, which come on instantaneously, so they are NOT as prone to thermal shock from being turned on. The tube may be subject to some damage from "cathode stripping" if the high voltage rail instantly powers up and the cathode is not yet heated enough to be emitting electrons. Better designs utilize a soft start circuit to prevent such problems, or if the amp uses a tube rectifier, the amp will naturally ramp up gradually. Overall, with most tube gear, there is more wear on the tubes from being left on when not in use than from the stress of being turned off and on more frequently.

What I never do is turn off an amp or preamp and then turn it back on without a fairly long interval in between (at least 10 minutes). I have seen tubes, particularly the rectifier, flash when this is done. While I have not noticed any permanent damage, this cannot be a good thing.

Highroller,

I don't know about your Lyr, but, a time delay mute is designed to prevent any output from the amp until it is warmed up and stable. Some tube gear will put out pretty nasty noise as it is powered up so a mute is designed to protect the speakers and your sensibilities while this is going on. The circuit does not necessarily also provide turn-on protection (soft start) for the amp itself; that is a separate feature. But, it is a good sign that the manufacturer is adding such features because soft start protection is even easier to implement.

George, what you say sounds reasonable, but I am not EE savvy. I can barely tell the difference between the front and back of the amp. :( Further, any mods to the amp's circuits will adversely affect its resale value.

My linestage and amp have a 12 volt trigger connection. The trigger starts the amp within 10 seconds or so after the linestage is turned on. I suspect this is NOT the same delay circuit you described. Instead, I think delay start-up prevents a linestage turn-on thump from causing a power surge through the amp into the speakers.

Otherwise, I think you and I are on the same page about turn-on/turn-off concerns. I'm not sure if 4 or 5 hours is a good number for my rig, but it's what I have been doing. Thank goodness I never had a Fourth of July problem with my gear -- at least not yet. Hopefully Ralph or Gary will weigh in.

Cheers,

Bruce

Al, can I assume, therefore, if one leaves their amp on unattended for even a short period of time, they could learn upon resuming their listening session that not only does their amp not work, they may be minus one or two speakers as well?? Al, there is obviously no written rule out there that I am aware of, ... but at the risk of too quick a turn-off/turn-on, what's your rule of thumb about leaving a tube amp on unattended?

Thanks

Bruce

I agree with Newbee, you do not have what most of us consider a "tube amp". Your Lyr is a tube headphone amp, which uses small signal preamp tubes, not power tubes. My tube preamp is on standby when not in use, there is always power to the tubes, unless I shut it off for extended absences or storms.

I would say that since your "amp" only uses two 6BZ7's or 6DJ8's, it is safe to leave on for an hour or so unattended. Warm up is 5-10 minutes, and you can leave the headphones plugged in when turning the "amp" off.