Should I use the Standby Switch on my tube amp?

Many years ago someone asked the following question in a gear group on Facebook… “How long do you guys let your amps warm up in standby mode? I used to go about 10 mins before switching it on. Now I’m doing it within the first 5 minutes, and no sound comes out for about 20-30 secs - is that the sign of an amp issue?”

I remember sitting there and looking at it for a while, and all I could think was “I don’t think I’ve ever been told about the real use of a standby switch - why it was actually there. I had always just turned the amp on and about a minute later flick the standby switch to on and away I go... When I (eventually) stop playing, I leave the amp on but flick it to standby”. This could be either a couple of minutes, between sets at a gig or even virtually all day when at home. I always thought “if your amp is on standby, everything is good”. The trouble is the more I thought about this, the more I realized I’d never even read what to do anywhere, I just did it – the same thing I’d been doing for years and years and years. I didn’t know if what I was doing was right, wrong, standard, naïve or anything else. I just saw the standby switch on my amps and used it the same way I’ve always used it on every tube amp I’ve ever owned.

Using the glorious medium of social media I put a question out on my personal FB about standby switches, their use and what would be the best way to deal with them, or even use them. I tagged some extremely reputable amp builders and asked the question “Can someone please tell me WHY we put valve/tube amps on standby”. I wanted to leave it generic, leave it open… Basically, I wanted to hear the opinions of the people who work in the business because let’s face it, 5 minutes on Google had given me so much conflicting information that I was about to switch to a Quad Cortex and be done with it. So, having posted the question I went away to do something else and when I came back didn’t expect the response I got; it would seem this is quite the talking point.

The simple answer to this question is there is no simple answer. It would appear that the standby switch is put in place mainly due to customer expectation more than anything else! Here are some of the choice comments from some of the guys.

First to respond (within seconds) was Roland Lumby from The Amp Clinic in North West England, Roland is the go-to man in the area for the maintaining and upkeep of your vintage and modern tube amps… He said “You put it in standby to stop it making a noise while the band takes a comfort break. There’s no technical requirement! Using standby means you don’t have to wait for the valves to warm up.” I must admit, this threw me a little as I was not expecting such a dismissive answer basically stating that the standby switch is just not ever needed. So, I read on…

Next up to offer something was James Hamstead of Hamstead Ampworks. “Better to turn the master down or unplug the guitar. Standby doesn’t do the valves any good. The cathode emits electrons, but they have nowhere to go, so they go back down to the cathode. It’s called cathode poisoning, and it will change the characteristic of the valves for the worse – noisier, reduce gain etc.” – The theory of cathode poisoning was brought up a couple of times. I must admit, this kind of made sense to me in a “sounds logical but I have zero scientific logic or reasoning to support my thought process” type of way. So, after this I started to think that maybe the standby switch would start to harm my amp rather than protect it?

Mike Fortin (who at the time I did not work) for posted this link which to save you trawling through it (you should, it’s great and not that long) had the following line: “Fender essentially misinterpreted the requirements, and everyone else copied Fender. Leo tended not to put anything into the circuit that he felt was unnecessary – but he came from a repair background where a standby switch is a service convenience.” This was supported by Jamie Simpson of Booya Amplifiers. So, obviously – the valves carry a lot of juice when they are in full flow so you’ll want to restrict the flow to a safe level when servicing them, so the standby switch appears to have been put in to protect the health and safety of the people working on the amps rather than any need in normal operation. The article even goes as far as stating that the best way to deal with your standby switch is “Bypass the standby switch internally so that it does nothing.”

After this the answers started to get more specific and silly (it is Facebook after all) yet some interesting points were made. 

“Unnecessary if your output tubes see 500v or less. If they see 800 like in a musicman (on not half) it might prolong their non microphonic life” (Harald Nowark).

“When you turn the first switch on you send 6.3 volts to the heaters… This warms the cathode which is treated or coated with material that promotes the expelling of electrons. By warming up the cathode before hitting the tube with high voltage it protects the coating on the cathode. When you take the amp off standby the big voltage hits the tube. Also, I think you should turn the entire amp off if you take more than a 10 minute break… No use baking your components for no reason when it only takes a minute to warm it back up….” (Phil Bradbury – Little Walter Tube Amps).

Questions were asked about unplugging speakers in standby mode “Still wouldn’t do it” (James Hamstead) and so on and so forth. 

This really jumped out at me “You see all those amps warming up before a concert? They’re not on standby… your amp won’t start to cook (class A amps excepted) without the HV on, the amp barely gets warm with just the filaments (when biased right, I must add). And… it’s not the tubes warming up that does the most for your tone… it’s the electrolytic caps… the ESR goes way down as the temperature goes up… so warm your big tube amp up good before you play. Standby is good for soft-start… cathode stripping is not really a problem with indirectly-heated cathodes (like all tubes we use now), so using standby and separating the HV from the filaments just lowers the inrush current, and doesn't really prolong cathode life. There have been wars fought over this, google cathode stripping for more. Cathode stripping happens to thoriated (directly heated filament) cathodes, found on large transmitting tubes.” (Stephen Cowell). 

“The standby switch is for convenience as a way of keeping your amp ready to go between sets or a quick way to mute when making changes to your rig. There have been millions of pieces of tube gear made (tv’s, radios, hifi, etc) that never had standby switches and worked just fine. If there is any validity to the “cathode stripping” theory, let me just say I have seen more tubes blown from the instant surge coming off standby than from improper warm up. And yes, an amp does sound better after it is fully warmed, but you don’t have to have a standby switch in order to warm it up. All this being said, most Shaw Amps will continue to be produced with standby switches for your convenience.” (Kevin Shaw – Shaw Audio)

In regard to Cathode Stripping, Roland made this excellent point: “During the 40s,50s and 60s, the best sound we heard was from a JukeBox. This machine stood all day, all week, for many years in the corner of the Cafe, waiting for the coin. How did it play right away? That’s right, it was on standby. The valves were heated by the main jukebox transformer .. The amp had a mains transformer which was switched off, it fed the rectifier valve which was directly-heated (usually a 5U4) When you put a coin in, the amp transformer was powered up, and HT would appear after 5 seconds or so, quick enough to beat the record onto the player. This meant that the valves were running the heaters continuously. Cathode poisoning was such a problem that they would have to put a new set of valves in the JukeBox every thirty-forty years!”

Trace Davis, head of Voodoo Amplification came in with this marvelous insight, not only into the industry but to tone. “When it comes to manufacturing amps it’s a great deal easier & faster to include a Standby Switch than to deal with daily emails & phone calls from those asking ‘Why is there no Standby Switch? My local tech said that’s bad for the tubes?’ As one can imagine daily emails & phone calls like this consumes a great deal of time so consequently most companies continue to implement Standby Switches as it’s more cost effective” and “To varying degrees this also enters into the topic of tone. Does an amp sound & feel better once the tubes have come up to temperature & the bias has settled in? In my very humble opinion, yes, so once you do engage the Standby Switch into the ready-to-be-played mode it takes a minute or so (depending on the design, how long the power switch has been on, etc) for everything to settle in to where the tone is consistent.”

To support this, Roland came in with “Trace is right about the amp sounding better when hot, particularly when the output valves get older, they don’t achieve full emission until the cathode has been heated for around 2 to 5 minutes. This is actually testable, and is not speculation”.

So, you know, I could rip apart all the comments by all the fantastic amp builders and repairers who contributed but instead I will summarize with the following, written in language that we can all understand.

Your standby switch is a hangover from Fender being more interested in the early days of repair and servicing. In terms of normal playing, in a normal amp, your standby switch is pretty useless. It’s just there as we guitarists expect it. Your amp will probably sound better after a few minutes once everything has warmed up and settled down. Cathode Stripping, do you want to risk it? I don’t, so I won’t be leaving my amp on standby when I’m not playing it. I’ll just turn it off (as like most people, my amps sits in that fraction of a millimeter between “Can’t hear it?” and “Ermhagerd!” so turning the volume down isn’t really an option). Please do not turn your amp on at all without the speaker plugged in and please – if you love your amp – give your tubes a few minutes (minimum) to cool down before moving your amp after use. And, of course, there are no user serviceable parts inside – leave it to the professionals!

And who said social media is full of cats, politics, beard combs and pictures of people’s lunch?

- Jason Wilding