Standby switch vs. leaving amp in run position vs. turning off

[Patrice B]

On a related note, we had a recent thread on an a vintage V4. If the amp was allowed to warm up in standby for a reasonable amount of time, it would work fine. If the standby was not used and the amp was simply set from off to "on, operate," the output tubes would red plate. Apparently it was taking longer for the bias supply to charge up than it was taking the B+ to charge up. So when the cathodes got hot enough to pass current, the tubes red plated.

We suggested using the standby on this amp. The OP sent the tubes back and got a different brand. IMHO, although the current tube are not red plating, I think there is a good chance they are still being exposed to high current while the bias supply is ramping up, and that ultimately this will reduce tube life IMHO it would be best to let this amp run in standby for a short period of time so the bias supply can charge up fully. Here is the thread if you want to read it. NAD: Ampeg V4

Oh, that’s me... Honestly, since replacing the two quads of Tung Sol’s with the Shuguang’s, I flip the two switches simultaneously but this is a good reminder that I shouldn’t maybe do this even if there is no more red plating. Ampeg manual (and Traynor too) recommend 30 seconds after power on if I’m not mistaken.

 

[Wasnex]

Wasnex: Agreed on all points other than leaving commercial electronics on 24/7. Back when I did that for a living, there were too many articles that supported less wear and tear on studio gear when left on.

Thanks for the tech info to all and this is just a knee jerk reaction during small tube replacement.
My SVT had a crackly pre amp tube.
I was disgusted by all the mismatched and no name brand tubes and took the opportunity to roll some vintage Telefunken 12AX7's in the pre amp and NOS GE 12AU7 driver tubes. The amp was apart for a week and I really don't think there was much change in the overall tone which has always been excellent. It does produce more SPL at the same position on the master volume pot but that may be the only change.

I think my only change in usage will be to turn the amp off if it won't be used for over an hour.
Will continue to go to standby before power on / power off, and also between sets (assuming we get to do that again)
@agedhorse
@beans-on-toast
Andy & David, any more thoughts on this?

IMHO commercial electronics may be intended for 24/7 service. I don't think that is necessary the same thing as leaving all of your studio gear powered up 24/7. In other words if the equipment is working, it's understood that the equipment has to stay on, and the gear will be designed accordingly with preventive maintenance that is specified at certain intervals necessary to ensure the equipment remains reliable.

My daughter used this argument on me with suggesting that I let my computers run 24/7. But I found that if I left the computer running all the time, it just meant I had to take it apart and clean and/or replace the fans more often. Had to replace a video card because the fan got linted up and I didn't catch it in time.

Also I have read quite a few articles on the subject and not come away with any sort of clear conclusion that leaving equipment on 24/7 always results in a longer service life. Don't forget I used to be an electronics technicians so reading about this sort of stuff was once in my wheelhouse. Here's an old paper that supports your position to some degree, but the answer is also fairly complex and nuanced (see attached). IMHO I think, again, the answer will vary from one piece of equipment to the next, and also vary with how frequently the equipment is cycled on and off.

Of course if you have your studio gear on a UPS that does AC to AC conversion and protects the gear from any sort of massive transient that may come in from the utility company, that would clear one of my concerns.

However consider this: AFAIK, small signal and rectifier tubes generally have an expected service life of about 10,000 hrs. There are 8,760 hours in a year, or 730hrs in a month. If you are okay burning through a set of vintage Telefunkens every 13.7 months just so you can leave the power on, I am not going to argue with you, but I don't recommend it as a general practice.

Output tubes generally have a much shorter service life of about 2,500 hrs. If you leave a tube power amp on 24/7 that means your going to burn through the expected life of the tube in about 3.5 months.

I think some cost benefit analysis would be in order. For example, if you are running a high volume studio that has clients every day, maybe it makes sense to leave high demand gear on 24/7. The studio would probably also have the gear serviced on a regular basis to ensure it's always in top running order.

Does this mean a player who cranks up his SVT once every couple of weeks should let the amp run 24/7? IMHO, the answer is no.

 

[agedhorse]

There sure are some interesting answers and "opinions" stated as "fact".

In fact, it's not nearly as rigid as it appears, and Leo Fender did not include standby switches because he didn't know what he (or his engineer) were doing, or that they were being cheap, or many of the rumors that seem to permeate such threads.

Here's how I see it, based on being inside the industry and having designed tube amps for commercial applications that had to be reliable and convenient to use:

1. Are standby switches necessary with tube rectifiers? Generally with tube rectifiers they are not necessary for reliability because any (reasonable) possibility of cathode stripping is addressed by the warm-up time of the rectifier tube and the soft conduction of the rectifies as it warms up and begins to conduct. I went back and looked at me Ampex (not Ampeg) service manuals to check that I was remembering things correctly, and many of the earlier tube amps (used in cinema and large scale public address) did not use standby switches. Most of these applications were of a higher level design than MI amps, so voltages and stresses were accounted for.

2. Are standby switches necessary with solid state rectifiers? Here's where the gray area begins to rear its head... if the voltages on the plates and screens are "reasonable" there's probably not much of a penalty for not using a standby switch, BUT as the voltages get higher there may be reliability benefits for using them. Also, the more an amp is turned on and off, the more likely that any damage would be cumulative. In the Ampex cinema amps that used solid state rectifiers but did not use standby switches, the voltages were generally more reasonable than many MI amps, and they are generally turned on and off a much smaller number of times than a guitar/bass amp. With some of the very high voltage MI applications, I believe that there are significant benefits because the amps are (or would be) generally turned off much more often than commercial applications.

3. Do standby switches protect capacitors? I don't think so because just as often the filter capacitors are located before the standby switch. The open circuit voltage of the supply is too high for the capacitors, that's a design issue not a capacitor or voltage issue. Especially these days, but it was true 50 years ago as well, the lifespan profile of an electrolytic capacitor is fairly easy to calculate.

4. Why may they be beneficial and why they are included (my opinion)? Because players often turn an amp on and off many times during a single days use. The cumulative damage may in fact accelerate the aging of a tube, but leaving the amp on (without standby) during that time would generate additional heat which accelerates aging of both the tubes and electrolytic capacitors. Since many of Fender's designs were with the tubes mounted "base up", this means that the heat rises and the chassis temperature increases. In standby, the power dissipated by the amp drops by roughly 50% which lowers the temperature of the chassis and decreases aging.

5. I think many players find it more convenient to place the amp into standby while fiddling on stage without waiting for warm-up when switching to operate.

6. The dreaded "vintage line voltage" issue... this is nowhere near as common as some folks would have you think. Going back through my service data, most vintage amps are designed for between 115 and 120V, with some tolerance for under/over-voltage. Today, the designs are even more refined in this regard because the safety regulations require testing at +/-10% of the nominal line voltage. These values are used when selecting components minimum acceptable voltage ratings. There are some exceptions, but there's much less in reality than the mythology might suggest.

So yes, standby switches are provided for good reasons, they are not provided because the manufacturer it trying to be cheap (in fact good standby switches are quite expensive due to the required voltage rating).

 

[walterw]

these days i mostly labor under the assumption that standbys are somewhat useful for high power amps, not so much for low power amps, and that letting the power tubes warm up a little so the heaters are fully running before kicking in the plate voltage might be a good idea.

i further assume that there isn't much point in any "cooldown" procedures, just turn the stupid thing off already.

hitting the standby just to unplug and switch instruments is silly; just pull the signal cable out of the amp a little, the input jack will typically short itself to ground and give you silence while you switch

 

[Rolling Thunder]

I feel that "standby" is not the correct label but since it goes way back probably 70+ years, that's what everyone uses (and therefore misinterprets).

I think of military vehicles that all start by turning a switch to "standby" or "wait" (with a corresponding light). When that light goes out, fire it up.

So for an amp, power up with standby engaged. Once the tubes are up to power, turn standby off.

 

[themickster]

Have a butcher's at this from an amp tech

 

[Matty4Strings]

That's because people are easily swayed by myth and urban legend. These pieces of gear are designed for 1000s or 10s of 1000s of power cycles. It makes ZERO sense that leaving the thing on for years at a time would somehow be better than turning it off and on under normal usage. How often do you switch on and off the lights in your house? And how long do lightbulbs last? Obviously not exactly the same, but it should give you an idea of how long electrical devices can last under normal usage.

Obviously, you probably shouldn't try to use the pilot light on your vintage tube amp as a strobe effect for a music video, but under normal usage, you will be fine.

Also, at some point, you have to wonder anyway when constantly applied voltage and current become more of an issue than turning something on again after a break. Think of a car. Sure, everyone just looks at mileage, but you could have a car with 5000 miles on it, but if it's 80 years old and hasn't been maintained, a lot of parts just deteriorate with time, not only with usage. So the key is to try to get the wear and tear of time vs usage in the same general time frame. It's not good if you never use the thing, trying to preserve it, and then time takes it's toll anyway. Nor is it good if you use it to death and it dies prematurely.

So I ask, all the purveyors of this pernicious myth, how many times of turning off and on again is it that destroys an amp (or other electrical device)? Is it 5? 10? 100? 1000? And at what number does it become completely ridiculous to triple your electrical bill to avoid a procedure your amp was designed to do approximately a zillion times?

It's my understanding that the reason some studios choose to leave their equipment on is to avoid the repeated heating up and cooling down of the solder connections. Over time, that makes the solder become grey and less conductive and it doesn't pass signal as well. I was also told by an engineer that the very large mixing consoles take a long time to warm up and they don't want to mix on a cold console.

 

[Wasnex]

I feel that "standby" is not the correct label but since it goes way back probably 70+ years, that's what everyone uses (and therefore misinterprets).

I think of military vehicles that all start by turning a switch to "standby" or "wait" (with a corresponding light). When that light goes out, fire it up.

So for an amp, power up with standby engaged. Once the tubes are up to power, turn standby off.

I have always seen the time needed to warmup to glow plugs in diesel engines called Preheat.

The Standby switch is labeled consistent with the definition. Standby means ready to operate. You turn the Power switch on with the amp in Standby, so the amp can be made ready to Operate. As a minimum this means the heater supply is turned on so the tube cathodes are brought to operating temperature where they can emit electrons.

Amps have three conditions that are determined by the position of the Power and Standby switches:
1. Off

Power Off, Standby Off​

2. Standby

Power On, Standby Off​

3. Operate

Power On, Stanby On​

When you set the amp to Operate, you are taking it out of Standby.

After you have played the amp for awhile and are ready to take a break, you can put the amp back in Standby, or you can turn it Off. Your choice.

 

[Figgystardust]

There are a number of reasons for and against standby switch usage depending on the circuit. Some tube amps are wired in such a way that bias voltage is not applied when in standby to the tubes mainly on older circuits and it also depends on rectification and filtering. There are so many variables.

 

[Redbrangus]

It's my understanding that the reason some studios choose to leave their equipment on is to avoid the repeated heating up and cooling down of the solder connections. Over time, that makes the solder become grey and less conductive and it doesn't pass signal as well. I was also told by an engineer that the very large mixing consoles take a long time to warm up and they don't want to mix on a cold console.

Edit: Pardon me; what I meant to say is I don't believe either of these concepts is rooted in fact.

 

[Roxbororob]

Oh, that’s me... Honestly, since replacing the two quads of Tung Sol’s with the Shuguang’s, I flip the two switches simultaneously but this is a good reminder that I shouldn’t maybe do this even if there is no more red plating. Ampeg manual (and Traynor too) recommend 30 seconds after power on if I’m not mistaken.

Salut Patrice!
Take the extra few minutes...(seconds) to flip the switches one at a time. Be nice to the old doll, she's a beauty!

 

[brianrost]

IMHO commercial electronics may be intended for 24/7 service.

Obvious examples are TV and radio stations, the Internet , medical equipment in hospitals, garage door openers, etc.

We may overlook that many of the devices in our homes are actually on all the time. How else can they respond to remote controls, maintain clocks and network connections, etc. My funniest device is a stereo receiver which can stream Spotify over wi-fi. If I am in the middle of listening to a playlist and put the receiver to sleep, when I wake it up, it connects to Spotify which restarts the playlist exactly where it was, even days later. That is pretty creepy

Of course, only a small part of the circuitry is running during standby, but the devices still draw some power.

 

[Patrice B]

Salut Patrice!
Take the extra few minutes...(seconds) to flip the switches one at a time. Be nice to the old doll, she's a beauty!

Yes, you’re right. It survived 47 years and I want it to outlast me so I will follow the advice from now on.

Thanks,

Patrice

 

[Redbrangus]

It's been a while, but when I was in TV audio as well as in recording studios, the equipment pretty much stayed on 24-hours a day. The "B" control room for a broadcast station where I worked had a 50's-era RCA radio console with 12 vacuum tube mic pre's that stayed powered up for years at a time - the only time any of the control room gear was powered down was for maintenance purposes. The logic in those cases is something along the lines of "if it's going to fail, it is more likely to fail on power-up than in use." If you consider how light bulbs tend to fail, you can see the reasoning.

OTOH, large-scale concert sound reinforcement systems are powered up and down every day -- sometimes multiple times in a day, due the vagaries of temporary power distribution, and this was true even in the days of dreadnaught-sized analog consoles. Admittedly, this is not studio use, but I've never heard of a console needing warming up.

To address the actual point -- of course you should use the stand-by switch on your tube amp, if present, when powering it up. I always just turned the amp down on the breaks back when I was using a Bassman for gigs, but that's also been a while...quite a while.

 

[dbase]

There sure are some interesting answers and "opinions" stated as "fact".

In fact, it's not nearly as rigid as it appears, and Leo Fender did not include standby switches because he didn't know what he (or his engineer) were doing, or that they were being cheap, or many of the rumors that seem to permeate such threads.

Here's how I see it, based on being inside the industry and having designed tube amps for commercial applications that had to be reliable and convenient to use:

1. Are standby switches necessary with tube rectifiers? Generally with tube rectifiers they are not necessary for reliability because any (reasonable) possibility of cathode stripping is addressed by the warm-up time of the rectifier tube and the soft conduction of the rectifies as it warms up and begins to conduct. I went back and looked at me Ampex (not Ampeg) service manuals to check that I was remembering things correctly, and many of the earlier tube amps (used in cinema and large scale public address) did not use standby switches. Most of these applications were of a higher level design than MI amps, so voltages and stresses were accounted for.

2. Are standby switches necessary with solid state rectifiers? Here's where the gray area begins to rear its head... if the voltages on the plates and screens are "reasonable" there's probably not much of a penalty for not using a standby switch, BUT as the voltages get higher there may be reliability benefits for using them. Also, the more an amp is turned on and off, the more likely that any damage would be cumulative. In the Ampex cinema amps that used solid state rectifiers but did not use standby switches, the voltages were generally more reasonable than many MI amps, and they are generally turned on and off a much smaller number of times than a guitar/bass amp. With some of the very high voltage MI applications, I believe that there are significant benefits because the amps are (or would be) generally turned off much more often than commercial applications.

3. Do standby switches protect capacitors? I don't think so because just as often the filter capacitors are located before the standby switch. The open circuit voltage of the supply is too high for the capacitors, that's a design issue not a capacitor or voltage issue. Especially these days, but it was true 50 years ago as well, the lifespan profile of an electrolytic capacitor is fairly easy to calculate.

4. Why may they be beneficial and why they are included (my opinion)? Because players often turn an amp on and off many times during a single days use. The cumulative damage may in fact accelerate the aging of a tube, but leaving the amp on (without standby) during that time would generate additional heat which accelerates aging of both the tubes and electrolytic capacitors. Since many of Fender's designs were with the tubes mounted "base up", this means that the heat rises and the chassis temperature increases. In standby, the power dissipated by the amp drops by roughly 50% which lowers the temperature of the chassis and decreases aging.

5. I think many players find it more convenient to place the amp into standby while fiddling on stage without waiting for warm-up when switching to operate.

6. The dreaded "vintage line voltage" issue... this is nowhere near as common as some folks would have you think. Going back through my service data, most vintage amps are designed for between 115 and 120V, with some tolerance for under/over-voltage. Today, the designs are even more refined in this regard because the safety regulations require testing at +/-10% of the nominal line voltage. These values are used when selecting components minimum acceptable voltage ratings. There are some exceptions, but there's much less in reality than the mythology might suggest.

So yes, standby switches are provided for good reasons, they are not provided because the manufacturer it trying to be cheap (in fact good standby switches are quite expensive due to the required voltage rating).

My thoughts exactly.... what you said

 

[Root 5]

I have had amp techs tell me that standby switches are completely unnecessary. Leo Fender made a mistake, possibly misunderstood the RCA tube manuals. Many TVs and radios used the same tubes found in amps, did your old TV have a standby switch? No.

Marshall used standby switches because he was copying Fender designs to some extent. Today amps have them because guitarists seem to expect them.

 

[dbase]

They should have just called them 'Mute" switches like my Mesa does. I used the standby switch on my old tube bass amps for when I unplugged the instrument cord from my bass. Had no idea it had anything to do with the tubes except I was told it lowered the voltage on the tube filaments.

 

[agedhorse]

I have had amp techs tell me that standby switches are completely unnecessary. Leo Fender made a mistake, possibly misunderstood the RCA tube manuals. Many TVs and radios used the same tubes found in amps, did your old TV have a standby switch? No.

Marshall used standby switches because he was copying Fender designs to some extent. Today amps have them because guitarists seem to expect them.

See my earlier post.

Circuits used in TV are quite different, and in fact standby circuits (automatic) are used in older TVs that do essentially the same thing as a standby circuit in guitar amps. They were used mostly on picture tubes, where the heaters were either fully or partially powered up without the high voltage supplies present.

In a TV, there are electron acceleration voltages in the many thousands of volts range, these voltages are generated with diode-capacitor voltage multipliers. Standby circuits extend the lifespan of these circuits while greatly improving warmup times, saving power and decreasing long term average temperatures.

Leo and others did understand the use of standby switches, especially as the industry transitioned from tube to solid state rectifiers.

Techs state an awful lot of things as “fact” without understanding the underlying history of the evolution that circuits have gone through incrementally. These are often the same techs that have not evolved to be able to effectively service anything but basic tube amps and I deal with some of these guys more often than I care to. Circuits evolve, techs need to as well, continuing education is essential to being a QUALIFIED tech.

Incidentally, the same thing exists in the automotive industry, the lack of continuing education has created a whole class of techs that are incapable of troubleshooting. They have become parts changers, guessing rather than correctly identifying. They also often state as FACT that the technology of the “good ‘ol days” is superior, not admitting that their OPINION is based on not understanding the newer technologies. Anybody here remember when an engine would need a rebuild after 50k miles and got 10 MPG?

 

[agedhorse]

They should have just called them 'Mute" switches like my Mesa does. I used the standby switch on my old tube bass amps for when I unplugged the instrument cord from my bass. Had no idea it had anything to do with the tubes except I was told it lowered the voltage on the tube filaments.

Generally, they remove (or sometimes reduce) the footage on the plates/screens.

Yes, there are still techs who think that the standby switch lowers the heater voltage. These are the same techs that don’t really understand how the various circuits in the amps actually work and just swap parts until the amp starts working.

 

[agedhorse]

It's my understanding that the reason some studios choose to leave their equipment on is to avoid the repeated heating up and cooling down of the solder connections. Over time, that makes the solder become grey and less conductive and it doesn't pass signal as well. I was also told by an engineer that the very large mixing consoles take a long time to warm up and they don't want to mix on a cold console.

This too is mostly urban myth, based on a small amount of truth.

Large format mixing consoles are solid state and are fully warmed up within a couple of minutes. Modern (past 30 years) circuitry is designed to be self stabilizing, one of the wonders of (good) solid state technology.