Tube amp standby

Tube amp standby DEFAULT

The Valve Wizard

Power and Standby Switches

Mains Power Switch
Every amp has a power switch. In fact, if you use a captive mains cable then you are supposed to include a power switch if you want to conform to UL/EN standards. It must switch both the live and neutral simultaneously (but the earth bond is never, never switched!).

If you use a detacheable mains cable (IEC lead or 'kettle' lead) then a power switch is not legally required. You can therefore use a single-pole switch if you want to, or even no switch at all (inconvenient!).

The power switch will need to be rated for use on mains voltage, and have sufficient current rating for the task. This should be no trouble; decent mains-rated switches are commonplace. Usually the switch is placed after the primary fuse, but this does not seem to be a legal requirement. A neon lamp is often added for power indication (optional, of course).

Standby Switches and Folklore
Many guitar amps (too many) include a standby switch. This is meant to let the heaters warm up before the high voltage is switched on. Old books called it 'preheating'.
But let's get one thing straight: a standby switch does not extend the life of the valves, in fact it is more likely to reduce their useful life. The valves do not care if you switch on the heaters and HT at the same time (with a couple of exceptions explained below). Now, I know what you're thinking, "but every guitar magazine in the land says the exact opposite?" Yes, they do, but guitar magazines know next to nothing about electronics, they just repeat the same old wives' tale each year.

If standby switches really did have magical life-extending properties then we would expect to see it mentioned from time to time in proper textbooks and valve manuals, yet such discussion is conspicuous by its absence. Indeed, some texts explicitly exclude audio valves from discussion of similar pre-heating switches (mainly with regard to radio transmitters). Despite this, promotional materials glorifying the supposed effects of standby switches are often published (always on the internet and in non-technical magazines, never in real academic work) even by well-known guitar amp manufacturers, presumably with good-but-misguided intentions. So such myths become self propagating.

You may have heard of 'cathode stripping', which is a specious argument wheeled out by standby-switch obsessives. In its purest form, cathode stripping occurs when particles of the oxide coating are physically torn from the surface of the cathode when it is exposed to a powerful electrostatic field from the anode. This would happen if the valve is operated at saturation, without a usual space-charge of electrons to protect it. Fortunately, this effect does not exist in receiving valves, even when operated at saturation, because it requires an electric field strength of at least 4MV/m (yes, 4 million volts per metre!). No guitar amp ever comes close to this.
Another type of cathode stripping occurs when stray gas molecules in the valve become ionised by the electron stream. The positive ions will then be accelerated towards the more negative grid and cathode. If these manage to miss the grid then they may crash into the cathode, physically damaging its surface. The proper name for this process is cathode sputtering. Sputtering is a known problem in gas tubes and transmitting valves operating at kilovolt levels, near saturation. It doesn't occur to any significant degree in ordinary audio circuits. Note that even the RCA Transmitting Tubes Technical Manual No. 4, p65, states: �Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature� [My emphasis].
Receiving valves are the small kind used in radio receivers, i.e audio valves like those in guitar amps, in case you were wondering.

Cathode stripping should not be confused with cathode poisoning. Cathode poisoning refers to chemical �rather than mechanical� processes occurring at the cathode. There are several forms of cathode poisoning, including absorption of gas into the oxide coating, but the most pernicious type is the growth of interface resistance. When a valve cathode is fully heated but no anode current is allowed to flow for long periods of time (several hours), a high-resistance chemical layer can grow between the cathode tube and the oxide coating. This has an effect like an unbypassed cathode resistor; it increases noise and reduces the useful gain of the valve even though the oxide coating may have plenty of life left in it. This really does happen in receiving valves, and once formed it cannot be removed again.

The two main causes of valve ageing are natural barium evaporation from the cathode, and interface resistance growth. Barium evaporation continues as long as the cathode is heated, so an ordinary standby switch has no effect on this. But a standby switch does encourage interface resistance growth. In other words, the standby switch is more likely to shorten the life of the valves!

And there's more. Valve (vacuum) rectifiers should always be allowed to charge the reservoir naturally from cold. If the valve is preheated before the reservoir is allowed to charge, the valve will have to supply the full inrush current when the switch is finally thrown. This is called hot switching and causes sudden cathode saturation that can lead to catastrphic arcing inside the tube. Hot switching of rectifier valves was usually forbidden by valve manufacturers. Opening a standby switch can also induce a ghastly flyback voltage across the transformer winding, large enough to cause arcing in a valve rectifier (a precaution against this is to add ordinary silicon diodes in series with each anode of the valve to reduce the reverse voltage across it). Yet more reasons why standby switches are bad news.

Standby Switch Origins
In almost a century of valve technology the only audio amps ever to use standby switches were guitar amps. Why? The trend began with the more powerful versions of the Fender Bassman (the 5E6 I think). Some people have suggested that it was primarily intended as a kind of mute switch, allowing the amp to be silenced between songs without needing to wait for it to warm up again before the next song. This is not a compelling argument since there are much cheaper ways to mute and amp without needing a heavy-duty high-voltage switch. Also, you would expect competing manufacturers to have provided similar mute switches on their amplifiers, but none did.

Another theory suggests the switch was added to amps which used silicon rectifiers because they did not provide the natural 'soft start� of the original valve rectified designs. This is obviously untrue, however, since the first Bassman amps fitted with standby switches were still built with valve rectifiers.

There are two plausible explainations for the added standby switch. One is that is helped to protect the power supply capacitors from excessive voltage before the valves start to conduct and pull the voltages down to normal levels. Fender often used a reservoir capacitor rated for higher voltage than the smoothing caps after the standby switch, which must have saved money and space. Take a look at the 5E6 Bassman for example. The 135 Bassman schematic even shows labelled voltages, exceeding the cap ratings during standby.
The other possibility is that the 5E6 was rhe first amp where Fender used a DC-coupled cathode follower. This stage will sometimes arc between grid and cathode at switch-on if the cathode has not yet warmed up. (These days you should put a diode or neon-lamp between grid and cathode to prevent this, not rely on the user).

Everyone knows Marshall copied the Bassman -complete with standby switch- so we then had the two biggest names using standby switches, only one of which knew why. The other big players, Vox and Gibson, traditionally never used standby switches. Only very recently have they given in and started adding them, presumably out of customer expectation, even though no modern designer (who values his reputiation) uses under-rated power supply capacitors. In fact, when Vox added a standby switch to its re-issue AC30CC they made the big mistake of putting the standby switch between the valve rectifier and the reservoir capacitor (something Fender was careful not to do). This hot-switching lead to several catastrophic rectifier failures on the first production run. Vox had to hastily add a resistor in parallel with the switch to allow the reservoir to charge up during standby (neatly demonstrating the pointlessness of adding the standby switch in the first place). This is just another way in which a standby switch can reduce the life of a valve.

Implementing a Standby Switch (The Least Bad Way)
Since this page has turned into an essay, let's sum up the pros and cons of having a standby switch:
1. Reduces the chance of exposing the power supply capacitors to excessive voltage (but you shouldn't be using under-rated capacitors in the first place);
2. Reduces the chance of arcing in direct-coupled valves, e.g. cathode followers (but you should be using a diode or neon lamp for this);
3. Provides a mute function (but you could just ground the volume pot wiper or something).

1. Can lead to failure of the rectifier valve (if the switch is between the rectifier and reservoir capacitor);
2. Leads to cathode poisoning if the valves are left in standby for long periods;
3. Can cause an unpleasant thump in the speaker when switching;
4. It's difficult to find switches with 'official' high voltage ratings;
5. Guitarists start worrying about how they are supposed to use the switch.

If you're still convinced that you want a standby switch then you can at least avoid poor implementations. First of all, don't make the same mistake Vox did. If you have a valve rectifier then the standby switch must be placed after the reservoir capacitor so the cap can charge up slowly as the tube warms up.
Leaving the valves totally cut-off, while heated, encourages interface resistance. A simple way to discourage this is to add a resistor in parallel with the switch to allow a trickle current to flow at all times, while still keeping the amp more-or-less muted. A 47k 2W device is a reasonable compromise. You can also add a 100nF (or so) capacitor across the switch to reduce arcing inside it. It is hard to find (attractive) switches which are rated for high voltage use, especially DC voltage, so most people just use a suitably heavy-duty mains switch. Since the HT current is quite small (hundreds of milliamps, not amps), this does not seem to be a problem.

When using silicon diodes we don't have to worry about hot-switching, so we can put the standby switch before the reseroir, which has certain advantages. Just as with fuses, switching a DC supply is much more stressful on a mechanical switch than switching an AC supply, because of arcing. Arcing leads to corrosion of the switch contacts and in extreme cases may even weld it shut. The switch will be subject to less arcing if is placed in the AC part of the circuit, e.g. prior to the rectifier. However, with a two-phase rectifier this would mean using a double-pole switch, which is a pain. A simple trick is to put the switch after the rectifier but add another rectifier diode after the switch, plus a resistor to reference the switch to ground. The switch then only handles rectified pulses rather than continuous DC, which is just as good as pure AC as far as the switch is concerned. Also, if a parallel resistor is added to allow trickle current then the diodes will enjoy a soft start as the reservoir slowly charges up through the resistor.

With a bridge rectifier the switch can be placed before the rectifier where it again avoids continuous DC. A parallel resistor again gives a soft start and will also have a (small) damping effect on flyback voltages generated across the transformer.


Amp FAQ: Will I damage my tube amp by not using the standby switch?

Paul Torquay asks: Hi Chris. Is it true that I can damage my amp by not using the standby switch? And if so, why don’t all amps have them?

Fantana: Valves have been around for nearly 100 years with millions upon millions of devices having used them, ranging from radios, TVs, hi-fis, radar equipment, mixing desks, submarines, tanks, warplanes – I could go on. Yet, the only audio amplifiers ever found with standby switches are guitar amplifiers. This, of course, is rather odd in itself but it is increasingly becoming the norm, and many guitarists now expect to see them fitted. It’s no wonder people are getting confused about them. What do they do? How do they work? Am I using it right?

The true origins of the standby switch are not quite clear, but they first appeared on the mid-50s Fender Bassman, around the same time that Leo Fender et al were upping the power from 26 to 40 watts. They simply switch the high voltage supply in the amplifier (B+ in the USA, HT – high tension – in the UK) on and off.

Old technical textbooks, military training manuals, and even academic research papers often talk about ‘preheating’ – allowing the valve to warm up before the high voltage is switched on. They do, however, include a very interesting exception.

The RCA Transmitting Tubes Technical Manual #4, p65 states: “Voltage should not be applied to the plates or anodes of vacuum, mercury-vapour, or inert-gas rectifier tubes – except receiving types – until the filaments or cathodes have reached normal operating temperature”. The part about Receiving Tubes is interesting because that is what we use in audio devices.

Ask The Amp Tech : Standby Switches

Merlin Blencowe – who literally wrote the book on designing valve amps for guitar and bass – says: “Let’s get one thing straight: a standby switch does not extend the life of the valves, it is more likely to reduce their useful life. The valves do not care if you switch on the heaters and HT at the same time.

“If standby switches did have magical life-extending properties then we would expect to see it mentioned from time to time in proper textbooks and valve manuals, yet such discussion is conspicuous by its absence. Indeed, some texts explicitly exclude audio valves from the discussion of similar pre-heating switches (mainly concerning radio transmitters). Despite this, promotional materials glorifying the supposed effects of standby switches are often published (always on the internet and in non-technical magazines, never in real academic work) even by well-known guitar amp manufacturers, presumably with good-but-misguided intentions. So such myths become self-propagating.”

If the books and experts say we don’t need to preheat the valves, why did Leo put one on his Fender amplifier?

One theory is that it was actually designed as a mute switch, but this quickly falls flat as there are quicker, safer, and better ways to implement that feature, rather than hot-switching 400-or-so volts! Another is that the 5E6 Bassman was the first to use a DC-coupled cathode follower, which is susceptible to grid-cathode arcing if the cathode isn’t warmed up – quite rare but it could happen.

Ask The Amp Tech : Standby Switches

My theory comes from a designer’s point of view. Having the ability to switch off the high voltage / high tension is incredibly useful when tweaking a circuit during the R&D phase, but also when diagnosing a faulty amplifier. This practice is quite normal and most of my prototypes will have a HV switch for that reason. I suspect this was the case at Fender, and they decided to leave the switch in situ for the production models.

Of course, we all know Marshall copied the Bassman circuit for their JTM45 and not long after Vox, Gibson, and eventually the others started adding them to their own models. Quite quickly, that simple switch became part of guitar amplifier tradition, much to many designers’ dismay.

Do you need to use it? No, not at all. Your amplifier will function perfectly fine without it – just leave it in the ‘play’ position. Can you use it? Sure, why not. But use it as the name intends, to place the amplifier in standby for short periods such as unplugging/plugging in your guitar. That’s it. Simple.

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Should I put my amp on standby?

A couple of weeks ago someone asked the following question in the Wampler Pedals Tone Group on Facebook… “How long do you guys let your amps warm up in standby? I used to play about 10 mins before switching it over. 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 sat there and looked 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, I just turn on, about a minute later flick the standby switch to on, rock out. When I stop playing, I leave the amp on but flick it to standby”. This period can 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 realised 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 current amp (Fender BDri) and used it the same way I’ve always used it on every valve amp I’ve ever had.

Using the glorious medium of social media I put a question out on out 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 (and some not so) 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… Wanted to hear the opinions of the people who work in the business – let’s face it, 5 minutes on Google had given me so much conflicting information that I was about to switch to solidstate as they are obviously much better and less likely to melt your face or burn your house down. So, having done this 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 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 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 bought 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?

Then in swoops Mike Fortin. Designer of signature amps of Ola Englund, Scott Ian and Kirk Hammett. So you know, he understands gain structures and valve amps! He just 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, doesn’t really prolong cathode life. There havebeen 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 Juke Box. 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 in 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 Juke Box every thirty-forty years!

Trace Davis, head of Voodoo Amplification came in with this marvellous insight, not only into the industry but to tone. “When it comes to manufacturing ampsit’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 asit’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 summarise 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 valves 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?

Tube Guitar amp standby switch demo Myth buster Marshall Fender



Standby Switch in Tube Guitar Amplifiers

The use and need of a standby switch is an issue that comes up from time to time. Let me say that a standby switch is a convenience supplied to guitar amps. Now not all guitar amps have standby switches. For example, the Carmen Ghia and its directly heated 5Y3 rectifier does not need a standby switch. By the time the 5Y3 conducts high voltage, the tubes are heated and ready to conduct. Extremely high quality tube stereo amps, like those made by McIntosh also don’t have standby switches. Remember that many stereo tube amp connoisseurs and audiophiles use these kinds of amps sans standby switches. I have never read an issue about the lack of standby switches on stereo tube amps.

So why do amps have standby switches? They are installed as a convenience for the operator. When a band would take a break, the standby switch was used as a “mute” switch for the amp. Once the break was over, the amp would be ready to play with the flick of a switch.

A few terms used to scare users into using standby switches:

Cathode Stripping: This term does not apply to the tubes used in guitar amps. This applies to cathode ray tubes, and only under limited applications.

Cathode Poisoning: In my 50 years of dealing with vacuum tubes I have never heard about this phenomenon. Cathodes only conduct electrons when the anode of the circuit has a high voltage potential to attract them. High voltage is present only when the standby switch is in “play mode”.

Here are some simple dos and don’ts when using a standby switch:

  • Always use a standby switch when dealing with a solid state rectified amp. The immediate surge of high voltage on a tube isn’t the best for its long-term life.
  • Power on your amp, then wait a minute or so and engage standby switch. This is the proper use of a standby switch.
  • Turn standby switch off if you are switching speaker cabs, engaging a half-power or triode/pentode mode on amps with these features.
  • Engage standby switch when taking a break.
  • When you power down your amp, just turn off power switch and leave standby switch on. This will safely drain high voltage from your transformer and filter caps for safe transportation.

Standby tube amp

A standby switch is a very straightforward and essential switch for guitars. The tube amps take time to get heated before they can produce stunning sounds. They work best when they are hot. Therefore your tubes need to warm up before you can crank it up and start playing.

You should turn on your amp in the standby mode to reduce wear and tear on your amp and also extend the life of the guitars. When the switch is set to standby, your amp will not send full voltage to the switch immediately.

One of the best practices is to turn the amp on standby as soon as you step on the stage. Read the following article to know how to turn on a tube guitar amp with a standby switch.

Keep The Switch Open In The Standby

You should let the switch be in the standby mode. Keep the power switch in the on state and then overturn the switch so that it(amp) can play(closed). By doing this you set the amp ready to play. Add a standby switch to the rectifier that is solid or a rectifier tube that has analternatecathode.

To do this follow the following steps:

  • Drill a hole in the structure and then insert a large switch.
  • Now cut the wires that attach the power transformer and the rectifier socket.
  • Now place in the switch

To know more about standby switches read the following points:

1.  Standby Switches Are All About Capacitors:

When the vacuum tubes warm up the standby switch removes the high voltage from the circuit. This happens until the time the tube filaments are not warmed up to the operating temperature and the power supply voltage is made equal to the nominal safe operating voltage of the capacitors.

Standby switches are a cost-saving design feature and offer a cheaper alternative than expensive capacitors. Before you switch the power to on make sure that the amp is set to Standby mode. However, do not leave it in the standby mode for more than 15 to 20 minutes.

2.  Use Standby Switch When Warming Up The Amp:

Do not use the standby switch as a beer break switch. If you want short breaks then turn down the volume control and do not use the standby switch. If the time taken between soundcheck and performance is more than 20 minutes then turn off the amplifier.

You just need 5 minutes to completely warm up an amplifier. If a positive voltage is applied before itsnegative charged electrode is fully heated, electrons will come off from the cathode’s oxide coating. This causesthe stripping of the cathode.

The standby mode was therefore invented to keep away the positive voltage from the plates till the time the tubes are not glowing heated. You can prevent cathode from wearing off by preventing the tubes from working till the time they have not reached a temperature when they can operate.

Use the standby switch when the amp or the power tubes are warming up. When the amp is heated up you can leave the standby switch alone. Anywhere from 15 seconds to few minutes once you are done with powering up, flipping the standby switch to on mode, you are ready to rock the show.

3.  Standby Switches Protect The Cold Tubes From High Voltages:

The standby switches protect the cold tubes from the high voltages. The process is known as cathode stripping. If a tube is cold and voltage is applied then the tube’s cathode is bombarded with ions and the coating is stripped.

This switch allows the tubes to warm up before applying B+ voltage. By allowing the tubes to warm up before you apply B+, their conduction will be instantaneous with the resulting voltage. The capacitor will never see a high switch-on voltage and will lead a longer life.

4.  Standby Switch Can Mute Your Amp:

One of the biggest advantages of standby switches is that they can mute the amp without turning them off. For instance, if you want to take a break set the stage to standby. This prevents you from turning on and off your guitar amp. This also prevents the tubes from warming up all over again. The tubes work best when they are warm.

A standby switch is not a break-switch but instead, it is used to mute the amp when you are on a break. It helps to prevent the excessive wear and tear of the valves. It helps the amps to warm up instantaneously after a break. It is essential when you are on a show with other entertainers so that your amp does not disturb your performance.

Standby switches also prevent the full voltage from reaching the tubes. This will give them the time to warm up and also protect them. When you turn on the amp make sure that the switch is in the standby mode so that no sound is produced while the tubes warm up. It helps to save expensive capacitors.

5.  Use A Combination Of DPDT Switch And Standby Switch:

You can combine and operate a DPDT Switch and a standby switch in one step. Use a wire to utilize one side of the switch for power and the other side for standby. Use the wire in a way that when it is in standby there is only alternating current and not direct current. In On-mode both alternating and direct current should be there. The switches turn off sometimes in the middle. Use a switch of 250 V AC.


You must have noticed that when you start playing using high gain and volume settings, your amp has a slightly different tone due to its cool temperature. There is less swell and less of a tendency to feedback. After playing it for half an hour there is sweet sounding. If this is what happens with your amp then use the standby rather than turning it off.

It won’t come off as fully sweet when you take it off the standby but within some time it will get back to the tone than starting its entire warmup process.

Related articles:

Standby switch on Tube Amp (SIMPLIFIED)

Tube Prelude: Warm Up to the Standby Switch

Right next to the on/off switch on many tube amps is a second switch labeled “standby”. It’s that switch that silences your guitar amp without actually turning it off, which comes in handy when break time rolls around at rehearsal or at a gig.

What you might not know, however, is that while that is a conveniently useful function of the standby switch, that’s not the main reason it’s there. First and foremost, the standby switch has a much more important role—protecting your amp’s tubes.

It’s kind of hard to believe that tubes are even still around. They seem so archaic—prehistoric, even—in this high-tech modern age of digital wizardry. Electric guitar amplification is one of the very few arenas in which tube technology still thrives, and the basics of tube operation haven’t changed much. Take warming up, for example.

Just like old radios, TV sets and the room-sized ENIAC computer of 1946 (which used 17,468 vacuum tubes), tube guitar amps need a minute to warm up after you turn them on. The science is pretty complicated, but suffice to say that tubes have to be hot in order to work (something about emitting electrons). In fact, they have to be really hot—like, glowing hot—before you can put a strong amount of electricity through them, and it naturally takes a brief period for them to reach their proper operating temperatures. If you turn a tube amp on and immediately crank it to full volume before the tubes have had a chance to warm up, you risk damaging your amp.

Therein lies the real utility of the standby switch. It allows the amp to be turned on but keeps full voltage from reaching its power tubes until they’ve had sufficient time to warm up, thus protecting them and prolonging their life.

You’ll notice that the switch itself usually isn’t labeled “on/off", but rather “on/standby". When you first turn your amp on, you want the switch to be in the “standby” position, in which no sound will be produced while the tubes warm up. Then, anywhere from 15 seconds to a few minutes after powering up, flip the standby switch to the “on” position, and you’re ready to rock at whatever volume you like.

At a rehearsal or gig, in fact, a good modus operandi is to first turn on your amp in standby mode, then go about setting up the rest of your gear—adjust pedals, run cords, tune up, order a drink, wash your hands and so forth. That usually takes at least a few minutes, after which you then flip the standby switch of your properly warmed-up amp to “on”, and off you go.


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