When to power off a tube amp?

Tomcy6:
"Many recent vintage tube preamps have a slow start cycle built in. It slowly increases the voltage going to the tubes over a 20 to 45 second interval when you turn the preamp on."

I think you'll find that's because they used tube recifiers, not solid state ones they use today.

Cheers George

Bifwynne:
Tube failure or arcing (flare up) happens in nearly all cases when the amp is first turned on from cold. This is because the HT comes onto a cold tube.

One way to rectify it is to get a 30sec delay circuit for the HT, so the heaters have a chance to heat the anodes and cathodes first. If you cannot build one yourself then there are many pre-made ones to insert on the HT rail.

Just Google or look in ebay for "Relay Delay Circuit" Do the math as you have high volts small current to give the relay contact amp rating you need. They can be bought for around $10 ready made. In the case of mono blocks you need two.

Or if this is too much bother, then just have another manual switch which breaks the HT so you can bring it on 30sec later, after the tubes have warmed up.

Cheers George

If you go out for just an hour or so leave them on. So long as you home insurance is paid up.

Turning off is not so much the problem, it's the turn on that is the tube deteriorator in most amps.
As nearly all of them bring on the heater supply and the HT(high tension) supply immediately. That means the HT hits a cold tube.

In nearly all the tube amps I've built I bought the heaters on first with the main switch and with a 30sec auto delay circuit then the HT was connected automatically. So there wasn't a sudden shock to a cold tube with the HT.

Cheers George