A refresher and reminder to use that standby switch. When a tube amp is switched on it should be run in standby for at least 30 seconds, preferably a minute (the longer the better) before applying the DC rail voltage to the power amp tubes. On Marshall’s, Fenders and most other tube amps, this is achieved by switching on the power at the main switch, leaving it for the necessary time, then switching from standby to normal operation. The results of not carrying out this procedure can vary from annoying, to downright expensive.
Annoying: Power Supply fuses may blow, particularly the DC fuse. Stripped cathodes in the power amp tubes will degrade the sound of your amp (see our Tech Tip from 12/8/2000 for background on this).
Expensive: Power Supply capacitors may fail. Bypass capacitors may fail. Your power amp tubes may only last half the time.
All this can be minimized by proper use of the standby switch. One common problem that leads to not following the above is switching off the amp at the end of a show/rehearsal by just switching off the main power switch. Next time the amp is turned on the standby switch is already on and DC is applied to the power amp tubes before the heaters have had time to warm up. Besides, it’s also a good idea to give your tubes some ‘cool down’ time in standby mode after it has been in operation. The standby switch is, without a doubt, your friend – put it to use!
