Use Huge Capacitor for Standby Switch?

[David Root]

Either way ya cain't win! I use standby switches because I like expensive old tubes. Therefore I protect them with a standby switch, costs max. $6.00.

You can't buy any kind of tube for that, let alone NOS or even good used old ones.

However I did not retrofit my '62 Deluxe with a standby switch, some things are just not done.

[The New Steve H]

Can I ask how you got 497? I assumed 710 was RMS straight out of the windings, but after that...poof.

The thing that concerns me about leaving the switch is that Mr. Blencowe seems to think it could actually harm the tubes.

On the other hand, leaving a cathode hot without any anode current flowing does lead to the very real effect of cathode poisoning, which reduces the gain (transconductance) of valves. Fortunately this phenomenon really only becomes significant if the valves are left on standby for hours on end.

I already have it wired up, but I could always dedicate it to some other function, like turning on a built-in fog machine or disco ball.

[ToneMerc]

Can I ask how you got 497? I assumed 710 was RMS straight out of the windings, but after that...poof.

710/2=355, which is each half of your HT winding.

355*1.41(s/s rectifier)=500V
355* 1.28 (true GZ34)= aprrox 455V , depending upon current draw

[diagrammatiks]

Can I ask how you got 497? I assumed 710 was RMS straight out of the windings, but after that...poof.

The thing that concerns me about leaving the switch is that Mr. Blencowe seems to think it could actually harm the tubes.

On the other hand, leaving a cathode hot without any anode current flowing does lead to the very real effect of cathode poisoning, which reduces the gain (transconductance) of valves. Fortunately this phenomenon really only becomes significant if the valves are left on standby for hours on end.

I already have it wired up, but I could always dedicate it to some other function, like turning on a built-in fog machine or disco ball.

this is true. don't leave your standby on for hours on end and you won't have a problem.

don't put too much stock in the standby switch. 30 seconds to 45 seconds is enough.

you've got cathode stripping from inrush current
cathode poisoning from leaving the heaters on...

but...don't forget that when you have everything wired up right...and you're amp is working...

you've got tube wear.

if the standby is already there. just leave it be.

merlin's just offering a warning against the advice to let your amp warm up for like 10 minutes and let it cool down for 10 minutes with the standby on.