what do you mean, standby not needed?

[Groover]

I have read, on a few different threads, posts effectively saying that standby is not necessary on low-powered tube amps. (Some of these posts involved amps with tube rectifiers which come on slowly, so warm-up is slow enough to avoid cathode stripping.) However I always thought that placing amps on standby helped to prolong tube life, and reduced wasted power and heat. I would think that with a SE amp, which has appreciable current flow even at idle, a standby would save tube wear, heat, and mains power when not playing the amp.

Is there no benefit to having a standby mode on the following ranges of amps?
a) SE amps < 10 watts, and b) small push-pull amps in the < 20 watt range; either fixed or cathode biased, either tube rectifier or diodes fitted with a NTC current limiter for less abrupt warm-up.

[Old Tele man]

...some people look at PI and see "3.14159..." others only see "3".

...the people who see only "3" are the ones advocating not needing a standby switch...they're right, but only to a point.

...others, who see PI as "3.14159...", tend to believe the standby switch contributes significantly to longer tube-life.

...of course, the question of "how much" becomes the arguing point.

[Hardtailed]

I use the standby to bring my SS-rectified amps on, but then I leave them on all night long.

The standby still turns the amp off, it just leaves the filaments on, keeping the tubes hot while not conducting. Long term effect is cathode poisoning but probably not really a problem.

Point is, that idle dissipation you set (unless you have a class B amp), well that's heat being dissipated through the tube, and it's usually more than what the filaments dissipate. WHen you switch to standby, you still get some "heat cycling" because your plate and screens will cool down a bit then heat back up.

There are as many reasons to use Standby as there are not to use it...

But you could read about the ENIAC computer. Once they decided to leave it on 24/24, they went from replacing a few tubes per day to replacing a tube every few days.

That said, I'd never build an SS-rectified amp without a Standby switch, but even that is useless according to some people.

[Groover]

"How much?" - I usually want 2 pieces, but if it is a big piece with ice cream that is probably enough! Sometimes sitting around with the family it will be n number of "slivers".

Sounds like its worth a few bucks for a switch.

[Enzo]

It won;t hurt anything to add the switch, so go ahead if you want one.

CAthode stripping is something they worry about at big 50,000 watt radio transmitters and stuff. At the currents and voltages in a little guitar amp, especially a tiny single-ender, it just isn't an issue.

SOme people think PI is 3.14, and some think it is 3.14159xxxxx. I think every high school had a science nerd who memorized PI to 100 digits or something. (Hey, I was a science nerd in high school, so I can talk) But if you want to know how long a piece of paper is needed to go around a beer can, do you really care about a couple thousandths of an inch?

And not all standby switches remove the power from the tubes. Some standby switches short the opposing power tube grids together.

One can say tube life is extended by use of a standby switch. Fine. But if the tube life is about a year, and you extend it 30 seconds, what have we accomplished? And that is the point. If you want a switch, have a switch. if you want to know why it doesn;t matter, that is why.

[Steve Conner]

As an engineer, I'd wrap the paper around the beer can, mark it where the ends meet, and then toss the paper and consume the beer.

5 reasons to have a standby switch:

1) It cuts down heat dissipation if you're only using the amp intermittently.
2) It mutes the amp when you're not using it.
3) It's effectively a 2-position step-start, decreasing inrush current because the power supply filter caps don't get charged until after the heaters have warmed up.
4) It allows you to get away with lower voltage ratings on your filter caps, for the same reason.
5) It supposedly eliminates cathode stripping, but I don't believe this. If cathode stripping were an issue, tube rectifiers would die from it, because there's a lot of equipment that has a tube rectifier and no standby switch.

5 reasons not to have a standby switch:

1) Needs an extra hole in the panel (an issue on my current amp build) or a 3-throw switch.
2) Hits the rectifier with a high surge current, if you wire it to get benefits 3 and 4 above. Silicon diodes don't seem to care, but I don't see tube rectifiers being happy with it. And it can make a gnarly "Thud... Bzzzzz..."
3) You shouldn't really be underrating the filter caps anyway, because people will sometimes operate the amp without any power tubes for troubleshooting purposes.
4) It's hard to wire it in a way that doesn't cause an audible thump or pop through the speaker.
5) You can leave the amp on standby for a month and get "cathode poisoning". I'm not sure I believe this either, though. I once worked on an old Selmer where one of the ECC83 preamp tubes only had one triode in use. So the unused section had heater voltage but no cathode current for the whole life of the tube. I wired the unused section up as a cathode follower to buffer the FX loop send, and what do you know, it worked fine!

From what I've seen, equipment that really needed a warm-up delay (mercury vapour rectifiers and the like) had it enforced by a time-delay relay, instead of relying on the user to remember it.

[jbrew73]

how about putting the standby before the screens as peavey does in some of their amps?

what pros/cons are there in this design?

[Old Tele man]

...in REAL ESTATE it's all about "...location, location, location."

...in ELECTRONICS it's all about "...application, application, application."

[d95err]

Even if you have a standby switch, you can never rely on people bothering (or knowing how) to use it. So components ratings must be the same regardless of if there is a standby switch or not. The inrush current can be limited by inserting a small series resistance (e.g. 10 ohm) before the first filter cap.

I think standby is useful as a mute-switch, but that's it. Muting can be done in better ways though.

[Groover]

Like turning down the guitar volume? or pulling the plug partway out of the input?

[Joey Voltage]

The ONLY reason why I would personally be compelled to put one in would be If I were trying to sell the amplifier. Musicians are horrible, awful people by nature. In their minds If you see a valve amp, you expect to see a standby switch regardless if it does a damn thing useful in practice, and educating them is an exercise in futility most of the time

The masses (i.e. the HC crowd type), and trolling competitors will just accuse your amp of eating tubes prematurely for that reason whether they really do or not, or use the opportunity to blame any unrelated malfunction on this and attribute it to incompetence...... so thats why I would put one in even if it is just doing nothing more than shunting signal somewhere

also, one thing to mention is that it is hard to undo decades of conditioning even if you were able to get through to people... even myself, I still wait to flip the standby switch and I *hope* I know better than to think it really makes a lick of difference, or that I'm prolonging anything else besides the sound coming out of my amp!

[Wilder Amplification]

The ONLY reason why I would personally be compelled to put one in would be If I were trying to sell the amplifier. Musicians are horrible, awful people by nature. In their minds If you see a valve amp, you expect to see a standby switch regardless if it does a damn thing useful in practice, and educating them is an exercise in futility most of the time

The masses (i.e. the HC crowd type), and trolling competitors will just accuse your amp of eating tubes prematurely for that reason whether they really do or not, or use the opportunity to blame any unrelated malfunction on this and attribute it to incompetence...... so thats why I would put one in even if it is just doing nothing more than shunting signal somewhere

also, one thing to mention is that it is hard to undo decades of conditioning even if you were able to get through to people... even myself, I still wait to flip the standby switch and I *hope* I know better than to think it really makes a lick of difference, or that I'm prolonging anything else besides the sound coming out of my amp!

By sticking with the trend you prolong your sanity.

[tubeswell]

I did a (tube-rectified) 5F6-something last year with no std-by switch, and it still works fine FWIW. The warm up time is really slow

But WTF, - a few PV tube amps are SS rectified and don't have a std-by switch - so, what Enzo says.

[d95err]

Like turning down the guitar volume? or pulling the plug partway out of the input?

If I was to add a mute switch, I'd make it ground the signal somewhere, e.g. just before the phase inverter. The switch would only have to deal with signal voltages, and it would be easy to make it automated if desired.

[Wilder Amplification]

If I was to add a mute switch, I'd make it ground the signal somewhere, e.g. just before the phase inverter. The switch would only have to deal with signal voltages, and it would be easy to make it automated if desired.

Just what we need...an amp that just up and automatically mutes itself.