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Tube Guitar amp standby switch demo Myth buster Marshall Fender
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- Опубликовано: 13 июл 2016
- I have received many inquiries regarding the use of standby switches. I do not use them in my amps. I have always believed that a tube rectifier protects output tubes by ramping current. This video demonstrates this theory. I am no scientist, just a tech with many years of self torture. Hope this video answers this question.
Holy moly. The purpose of the standby switch is to cut the stage volume off and on without hiss and ramp up. I have a Marshall 50 watt that I've had for decades. Had more problems with the power supply and the the occasional pre amp tube than I EVER had with a power tube.
It and its 4 X 12 even toppled over backwards into the street and were fine.
No issues here.
when I used to play out professionally.. I also toppled over backwards one time..... I hate it when that happens....
Great, simply great! I did not use my standby switch on my fender tube amps just for this reason. In guitar amp app it is complete useless. I worked in the 60's with tube powered radio transmitters and than you must use the standby switch! The whole myth is in mine opinion started by Leo Fender. This man was in his early years a radio receiver/transmitter technician. So on his first amp he placed the standby switch because he was used to do this with transmitters. And every amp builder followed him and created a story about the standby switch. So glad that you let see what happens. I do not think the big brands will follow this because the guitarist demands a standby switch. lol great video's. The only thing you can do is read the post from Trevor below. You are sparing the filament with a NTC resistor.
Thank you for the straight forward, no non-sense video. I enjoyed your demonstration of the warm up characteristics of the GZ34 rectifier tube. Not ashamed to admit I was raised on the whole “standby” as tube life preserver story as well. Really makes sense when you ask, “where were the standby switches on old vacuum tube tv’s and radios?”
Because their valves where wired in series not parallel.
Love your vids! Great explanations and demos. I’ve learned tons!!
Thanks a bunch for doing these
This is an interesting subject. I've told many of my tube amp customers (especially one's who owned an amp with a tube rectifier) to leave the standby switch contacts closed and use just the power switch. I recall one incident where a customer with a Dynaco Mark-3 power amplifier. He had a technician install a stand-by switch. However, he placed the switch in a bad spot. He lifted the grounded center tap on the HV secondary. That's not a good idea especially if the bias supply is derived from a separate tap off the secondary. It can cause a rise in voltage across the bias filter cap which can cause it to fail. The bias filter cap in this amp was rated at 47uF at 160VDC. When the standby switch contacts were opened, the voltage rose to over 250 volts.I just disconnected the switch and re-soldered the center tap back to chassis ground. Another good video that proved yet another valid point! Keep 'em comin' Frank Ferraro--Audio Craft Electronics :)
Thank you for sharing this info Frank. I am honored to have your support. More vids in the works, just need some spare time.
I am also wondering why the Marshall amps do not have a high failure rate on the standby switch. The switches have a rating of 250vac. I believe in their application, double that is applied to the contacts. Surprised the switches don't arc. Have you ever run across that situation? 500 vac at the tip of your finger! Zapp!!
I've had failed stand-by switches in the past, but not a frequent occurrence. but I've had blown screen resistors, from shorted output tubes, and blown HT windings on the PT. A lot of the Marshall models, use a separate DC supply for the preamp tube heaters, and I've had many failed rectifier bridges due to the way they're mounted. They push the bridge flat on the PCB which leaves no room for heat expansion, and no heat sink is on the bridge.. When I replace those bridges, I elevate them off the board for air to pass under them and install a clip-on heat sink. Problem solved! :)
Man, that's some great info. Any chance you could shoot a video the next time you have that repair situation? RUclips is a great place to help each other with tech tips.
I'm trying to get properly set up to shoot video, sometimes it difficult when it gets busy, and my shop and bench is such a mess, it's embarrassing :)...but I'm working on it :) I don't mind sharing tech tips to brother technicians...I'm in a secret tech group that I can't talk about here, but hit me up on Facebook (we're friends there already), and I'll fill ya in on getting in it. There's a plethora of knowledge with some of the best techs in the business...
@@djfrank59 yes I have a dsl 201 that has that problem hasn't failed yet but not sure if its been addressed as I bought the amp used.... Guess I should open it up and have a look not good engineering on that lol
Yep! 100% agree. Plus I have two blackface fenders from the 1960s that have two filter capacitors before the standby switch. When the amps are in standby those caps, which are rated at 450 volts, have 500 volts sitting on them. I've disabled the standby switches in those amps and now the voltage rises slowly and does not surge.
I re-capped with higher voltage caps because of this very thing.
A very brief excursion (current spike) through the rectifier or output tubes is harmless.
The real trouble with "standby" is the resulting over-voltage across parts of the power supply, namely the filter electrolytics, as most of the load is removed from the supply.
Bad mojo.
Also, have a close look at the ratings of the "standby" switch; not at all rated for the DC potential across (nor through) it. The closing of it isn't so rough on it, the opening of it IS. Bottom line? Nix the switch. Turn the volume down instead.
Thumbs-up, D-Lab.
And there's no reason you can't have a mute switch that simply sends your signal to ground instead of a standby switch.
This should work we don't have to be engineers to use an amp, so for our mortals what is the final advise? Don't use stand by?
Just pull your guitar lead jack out of the amp while you're on your break. Replace it when you return. Simple as that. Standby switches aren't necessary.
@@castleanthrax1833 I was going to post the same reply!
@@castleanthrax1833 While it's a good idea, it is of no help for at least the following situations:
- An amp with Reverb getting slightly bumped into will still produce a loud Reverb Spring noise.
- While unplugging the Cable from the Amp's Input helps reduce the vast majority of noise, a powered Tube Amp without being on Standby (I'm not advocating for Standby Switches here) will still produce a pretty good amount of hiss and noise. Even the quietest Amps still produce noise that is very noticeable at Stage Level (imagine if there were 5-6 Tube Amps on stage all producing noise... It would be irritating during the breaks.). Also, when on Stage, Tube Amps pick up all kinds of EM noise from the environment... Even happens in some Studios.
I have used various strategies over the years to try to avoid noise on stage while not playing, I must admit that most often I've also been leaving my Amp running open instead of putting it on Standby.
This I usually do with my Rackmount Amp as it's DEAD quiet and there are no risks of someone shaking the Reverb Tank as it's in my Rack on top of 2 Stacked 1x12" Mesa Recto Cabs.
I do however usually turn down the Volume Knobs to Zero. I also use the Mute function from my Tuner and/or engage the Mute button on my Planet Waves Circuit Breaker Cable and leave it plugged in when I'll be using the same guitar after the intermission.
When I use a Combo, especially my Mesa Subway Blues (Class A non Master Volume monster of a little amp that runs its pair of EL84's EXTREMELY HOT, which is awesome as I use Power Amp Tubes Distortion with this Amp, but it chews through power tubes fast), I engage the Standby Switch after muting my rig in one of the 2 previously mentioned ways to allow small amps that run hot to cool down significantly.
I'd still like an alternative to the Standby Switch!
It's now 7-22, I haven't seen this video before now. But I disconnected the standby switch in my 1958 Fender Bassman decades ago and it's just fine. I also quit using the switch on my pre CBS Fender S.R. and D.R. and other Blackface Fender amps I've owned many years ago too, and they're fine. I change the electrolytic caps every 8 to 10 years, filter, bias, and cathood bypass (I've owned and used my old Fender amps since the early 70's, making a living as a pro-guitarist, working several nights a week, I'm not a hobby player, my amps have tons of hours on them). And my tube life is generally normal, in fact I have GZ34s that are from the 60's and 70's still working fine in my old amps. I think standby was just something added for a selling feature, they seem inexpensive for the factory to add, but might make the potential buyer think he's getting an extra bell and whistle. The big pop you get on some amps when you use the switch made me think it wasn't a good thing, that's why I stopped using it. Also on the 'tweed' Bassman there's a capacitor wired to ground that I thought might short high DC to the chassis if it failed, but I'm not sure of that (I just took the wire of the switch and bypassed it to the tube. On that subject, I converted all my old amps to 3 prong and removed the widow maker capacitor decades ago ( I knew of a kid who was killed by his Super Reverb back in the early 70's). Terry, thanks for giving us proof. Good video as always.
My use of the standby switch was for idling the power tubes when going on break after playing an hour set. Flip the Super Reverb on standby for twenty minutes...then flip the standby back off and start rocking and rolling again instantly.
Exactly. Band walks back on stage and immediately starts……
That’s what I thought it was for
Wow how did you ever figure that out ?
I’m not a “gigging” artist, and this is exactly what I do between my “mental rock star” practice sessions…basically, I keep the tubes warm between my practice sessions when I need a break. When I plan to stop practice for more than a “few hours/overnight,” I turn off the amp entirely and let everything cool off.
Admittedly, I have a lot to learn from other, more experienced, players.
Also, I spend a lot of time practicing improvising leads over .mp3 backing tracks played through my SS Orange practice amp…which has mostly no relevance in this discussion…
…wow, this derailed really fast…
If you have a solid state rectifier you will hit the tubes with a spike no matter what. The value of the standby switch in this case is it allows time for the tubes to warm up BEFORE the spike hits them. (the filament circuit bypasses the standby switch) I understand that current (and voltage) spikes do more damage to a cold tube than they do to a warm one.
Thereby eliminating cathode stripping?
Oh man
what did you do in electrophysics class at school?! :D
After all, it's not about inrush currents after switching on and the steepness of the voltage rise - this is a matter that causes a problem mainly for the smoothing capacitors behind the rectifier.
The main reasons for using a standby switch are two basic:
The first reason is for use in live performances, when a musician cannot afford to wait 20 seconds after arriving on stage for the amplifier to warm up to start the show.
That would not be a very triumphant entry on the podium :-D
Also, sometimes you need to turn off the amplifier for a short time if you need to reconnect a faulty cable during a performance and continue playing immediately after the replacement, etc.
This is the first reason for using a standby switch, to be able to turn the tube amplifier on and off as quickly as a solid state amplifier.
The second reason to use a standby switch is important to protect the emission layers of the cathodes, and that's the thing you missed in electrophysics class.
If you operate the tube in underheated or overheated mode, you damage the emission layer of the cathode.
In overheated mode, you damage the cathode by evaporating part of the emission layer and creating an imbalance between the representation of barium, strontium and oxygen atoms in the composition of the emission layer.
In this case, the cathode is damaged, but not as damaged as in the opposite case, when the cathode is under-heated.
However, a significant problem with overheated cathodes is that barium and also strontium settle on the tube grids and then grid emissions occur on those grids, which is a relatively serious problem, especially if this occurs on the first grid.
Well, now the problem that arises when the cathodes are under-heated.
If the cathode is underheated, the cathode emission layer tends to accept more oxygen molecules than is set in its composition at the end of the activation process during manufacture.
And this imbalance causes a reduction in the emissivity of the cathode = the ability of the tube to transmit the full dynamic range is reduced.
I know that an uneducated amateur could object to me that there is no oxygen in the tube because it is pumped out and its last remnants are captured by the getter, but in fact there are enough oxygen atoms in the tubes, which are released mainly from the anode plates, some atoms get to bulb of
tubes through microvents in glass, etc.
Well, that's just the fact that if you don't use the standby switch, for the first approx. 20 seconds you operate the tubes in under-heated mode, so every time you switch on the device, you cause excessive aging of the cathode emission layers of the tubes.
So I hope you don't get mad at me for disagreeing with you and presenting it publicly like this, because I also dispel myths and it's important for me to do that because people who follow us learn from our posts.
And one of the worst things is when you learn something, internalize it deeply, and then you have to relearn it ;-)
Many greetings and much success in your work.
Indian of Louny
Nice to know there are people still interested in this phenomena after six years. I am not an electronics educated person, just a player, every other comment makes me change my mind back and forth lol. Since you are a proponent of using the standby, what about when turning off. I was told to turn my marshall plexi style amp off with bypass off in order to let the caps discharge or something.
My Carvin X tube amps are now 40 years old and the standby has been used in various ways at home and for gigs. I’ve replaced only tubes and a single power switch over this time. Yes these amps should be gone through at this point but both are still sounding killer and everything works!
I think the purpose of the standby is to prevent excessive high voltage sitting on reservoir cap and filter caps until the tubes are heated enough to draw current. When the tubes aren’t drawing current the b+ is a lot higher. And then if your wall voltage is higher than normal you can expect even higher b+ on the caps before the tubes draw current. And in tube rectified amps the rectifier doesn’t put out b+ until it’s warmed up and the preamp/otpt tubes are usually ready to go by then. Solid state is immediate and doesn’t give output tubes time to warm up to draw current.
Since old fender amps should be re-capped anyway, replace with higher voltage filter caps if a person wants to use the standby switch. Modern caps are smaller and higher voltage caps can fit into same space. Probably a good idea either way in case you sell your amp to someone else. Also, it is so true that modern line voltage is higher by at least several volts AC which increases the B+ by multiple of the B+ output voltage (and rectification process). I myself don't use standby switches. I actually soft start and run vintage line voltage level with a variac when at home. Playing out would be a different story!
Not so, see my previous post. Also, if you are right, how come guitar amps, and many type of pro equipment, have always had standby switches, before solid state rectifiers were available? The purpose of the standby switch is to make the amp dead quiet while keeping it ready for instant use. Not so important for bands playing in pubs and taverns, but for TV and stage it IS important.
The voltage on filter caps (and coupling caps too) does rise above normal when solid state rectifiers are used, but competent amp engineers working for reputable brands allow for it when choosing capacitors. Filter caps often have two voltage ratings - the maximum working rating (which should not be exceeded during long periods), and a surge rating, which is higher and is permitted for switch-on.
Capicitors are typically overrated. True but the actual problem is cathode stripping. Same as on xray devices we use in our hospital. Nothing to do with mute or cooking your tubes nonsense. In this scenario SS rectifiers are problematic and tube rec allow slow ramp up. Because itself needs to warm up.
@@Nightingale1887 : You are just repeating an urban myth. As I said, vast numbers of vacuum tube TV's and stereo systems were made with silicon rectifiers, and no impact of tube life was ever noted.
High power tubes used in transmitters are another story. So would be X-ray machines, because of the high voltages used (20 to 200 KV in medical diagnostics), which can cause field emission before the cathode is hot and ready. (In fact, in very early X-ray machines, they used pure metal cold cathodes, relying on field emission.) The 300 to 500 Volts or so used in amplifier power stages, and the 10-150 volts of so used in other amplifier stages is just far too low to cause field emission and thus there is no problem.
If standby switches are not for muting, how come guitar amps and professional studio gear have always had standby switches, long before solid state rectifiers became available? Unless you can answer that, your post is worthless.
Bon appétit ! All that is great, but I don't know any guitar player with a tube amp like me, that has an oscilloscope at home.
On a Fender amp, turning the volume pot to zero leaves the last three stages of amplification and the entire reverb circuit active. If the band takes a break and the amp isn’t dead quiet, that noise may be annoying. And someone bumps or moves the amp during break, the reverb spring will crash. A standby switch eliminates both of those issues.
What's the advantage of a standby switch versus just turning off the amp?
@@slayjah2 If a break is short I’d prefer to keep the filaments hot. It’s not big deal, but I prefer to have a standby switch.
The Cadillac of power sources next to the Cady of chucked-drills..
Always finding a way to make me love your channel even more haha🎉💜🙌
Thank-you man, keep up the amazing work🙌⚡️🙌
👍 thank you for actually explaining this and your obvious knowledge.. appreciate it 👍
Great video , as always Terry !
Great straight to the point video! Thank you!
My standby switch is on just long enough for me to grab my guitar and plug it in. I'll use it at the end of the session when powering down to avoid unwanted hiss, pops, or squeals. Never had an issue.......yet!
Well, I was taught that the purpose of standby is not to reduce the spike, but to enable the tube to better withstand it, and reduce cathode stripping, by pre-warming the components.
You won't get cathode stripping on valves made for amplifiers. Cathode stripping occurs in the 1kV range; amplifier valves don't normally go over 500V.
I think the best example is looking at either modern valve HiFI systems or old TVs that used valves. You won't see a standby switch on them because it's an unnecessary feature for a device that runs on such a low voltage.
Cathode stripping would be more of an issue on a high powered tube RF transmitter. Standby switches are required for those types of amps.
If a standby switch was needed on musical amplifiers then my Wurlitzer spinet organ from 1964 would've needed it's tubes changed out a loooong time ago. The organ still uses the two stock 6L6 tubes and the stock rectifier tube it came with from 1964 and it has no standby switch.
However, cathode poisoning can occur on tubes in standby for long periods of time. Cathode poisoning will not happen if the cathode is allowed to have electrons flow out of the filament, so using a mute switch prior to the amp or turning down your guitar will actually prolong the life of the tubes better than a standby switch. Standby switches are more of a die hard tradition on guitar amps than serving a useful purpose.
@@CorvetteCoonass With tube diode you haven't B+ untill diode tube is warm so the output tube is warm when they receive B+. By the way stand-by switch exist because you can "turn off" the amp without waiting when you will "turn it on" again.
Great vid, Terry. Thank you. So what about tube amps without standby switches, like a Fender Blues Jr or Pro Jr?
there are some potentiometers that have an included on/off switch, could be good installing one of those switches as a volume pot and standby switch at the same time?
That was cool and good to see! Thanks!
In HiFi amps we often use a soft start relay, that switches in a resistor to start up slowly, and then switches it out again in a second or so. That relay can be put in a separate box, and
the ´standby switch´ has to be on, when turning on the power. A fix to be able to use the stand-by switch when power is on, could be to put a NTC (thermistor) in series with the stand-by
switch. Many of those are rated at 5A. The NTC data sheets though does not show a max voltage, and I haven´t tried it yet. I find it practical to use a stand-by switch when changing cabs
and other stuff.
I'm confused because of the way standby switches are labeled. They seem backwards. Is this video saying to power on the amp with the standby switch in the position that lets the amp make sound? Like if it didn't have one? I have a 68 Bassman that hasn't been played in 20 years. I want to get it serviced soon and treat it well so it will last a long time.
Would a Twin Reverb with solid state rectifier apply as the Marshal example?
So, that high initial in rush current would be due to ss rectifiers having low source impedance, and the power supply having a relatively high capacitance in the Marshall?
I just fried mine in last week vid when I plugged my portable A/C in the back and started it up soon after jamming... it blew some smoke and now won't power on... can you fix my Ampeg VT-60 or have an extra mani power transformer sitting around?
very interesting. I'm glad I subscribed some time ago :)
so you think it could be possible, that all these artifacts might have been made in around the same time and got stainless by accident?
or did I not follow you right?
Some amps only have an attenuator than a standby switch (e.g. Marshall Origin and DSL). Does the attenuator do the similar thing to a standby switch (cuz attenuator can turn down the amp to small watts like 5 or even 1/4, under which situation a standby switch is probably not necessary)?
In my (admittedly very limited) experience, I see more tube failures of the filament than anything else and it's predominantly on initial power up when the filaments are all cold and thus have their minimum resistance. I've found that placing a small NTC (such as those used to limit inrush current on an SMPS) in series with the filament supply dramatically lengthens tube life. The actual difference in filament voltage once it's warmed up is pretty negligible (around 50mV less on the few I've measured)
While it's perfectly possible to incorporate a solid state 'soft start' into the B+ rail, I'm unsure how many tubes it would have saved me over the years... Not many though!
Sorry can you speak English?
@@flintdavis2
Yes, I can INDEED speak English.
When making a slightly more 'technical' post, I tend to type with a somewhat more 'advanced' English than you might be accustomed too.
Hi, I have a Bugera V22. It burst the power tubes very fast. Do you have an idea of what could it be?
If an amp is dead cold and you only have an on/off switch along with silicon diode rectification. Will it still spike? Maybe I am confusing the time it takes filaments to warm up with what you’re talking about?
I added a standby sw.
To my fender champ
On the back and found
That out but the only
Reason I put it in was
To prevent feedback
When setting the guitar
On the stand next to the amp you can walk
Away leave the volume
Up on the guitar and or amp without getting
Feed back.
The amp doesn't
Howl when you turn
The standby sw. Off
It allows you to have
Instant on off.
But yes it is not good for the rectifier tube.
I also have a tube
Tester a Night 600
Not the best but it can test for shorts
And emissions output
I don't mind the extra
Expense if I have to replace the rectifier
I have spares. But the
JJ 5Y3 has lasted 25
Years sofar. I have a
Question about the
Noise filter death cap.
Can you put a 1meg
Ohm resistor in series
With it. To reduce the shock hazard and still
Reduce line noise?
Using the standby switch on a tube guitar amp during normal operation is not only unnecessary but can shorten the life and/or performance of your tubes. Having the tubes hot and the cathodes emitting electrons without the tubes conducting current (and the electrons having no place to go) is not a good idea. Cathode poisoning (as was mentioned in another comment) is the result and it is a very real phenomenon. The standby switch is handy for maintenance and repair purposes (to verify bias voltage at the grids before applying B+, for instance) but that's about it.
Thank you for explaining what cathode stripping is and does.
Cathode stripping and cathode poisoning different things?
@@tomdrouhard3781 Yes. Cathode stripping doesn't happen in tube amp tubes, but cathode poisoning can.
Thank You for the video.
Should I not use the standby switch on my music man hd130 combo amp?
I think the standby is mainly just for band purposes so you can just come back and the amps are ready. I mean I guess if left on could be no difference, but then you can get accidental noise which you might not want to be possible at a professional show.
I’ve never used standby on any of my tube amps. I just leave them on and use my Boss Tu-3 as a kill switch on break. I’ve never had any problems.
What about the more important question. Turning the amp off.
I turned the standby off on my valve king once and the master a bit too soon afterwards.
Massive pop and really made me jump.
Ever since it's been standby off, wait a minute then master off.
This was my thought as well after watching the video as well. A friend at our local jam night is always saying to switch the standby a couple of minutes before the main to allow some cooling? Video was informative, from now on I will switch main and standby together to switch on and standby then main to switch off. Fender Pro Reverb
Love watching these amp tech videos even though, apart from some rudimentary maintenance I have no intention of diving in.
I have a Marshall JVM410HJS, Friedman BE-100 Deluxe, Mesa Boogie Mark V 90 and a Peavey JSX. I have been using standby switches forever because I've been told it saves your tubes. So should I use the guitar volume or master volume on the amp?
Very good video!
I usually like to bring up my equipment on a variac over the course of 10 seconds or so.
Do you think this would help with inrush current?
Thanks :)
Yes, the variac is always a good idea on older amps since their input AC voltage was lower back in the day
No...dumb idea. The amp is built to handle inrush. You have bigger problems if you are blowing fuses from inrush current...like weak/leaking power supply caps. Lowering voltage....increase current. Bad for transformers on a regular basis.
What about larger Fender amps like the Dual Showman or Twin Reverb?
I solved this problem by ... Switching to transistor based amplifiers! I got sick of switching my AC30 from standby and popping rectifier tubes on stage in front of an audience.
My 1988 Award Session SG75 has never, ever, gone wrong. It's only had two service items since new: the input jack, and the clean channel master volume pot. That's literally it.
You're forgetting that solid state amps sound like solid state amps. Unless you play elevator music that's a bad thing
Terry, are you suggesting that we not use the standby switch? Just leave the standby in the “on” position all the time and toggle the power switch to turn the amp on and off? Same on a Vox AC30 with GZ34 I assume? Thanks a lot.
A solution I saw the Guitologist use is a thermistor between the standby switch and the first power filter stage. It limited the current until it got up to temperature, reducing the magnitude of the spike. This may be a worth-while mod to put in my 2204 clone, as I didn't know the standby switch could cause a surge on the output; with all subsequent power stages being resistor- or inductor-limited, I didn't think the current spike made it past the first filter stage.
For anybody designing tube amps, standby switch or not, a good choice is to build a soft-starter into it; basically a constant current source configured as a current limiter, such that when the current draw drops below the limiter's threshold, the limiter is wide-open, "trying" but unable to shove more current through the load, letting it draw current unimpeded. It will only impede current flow if the load tries to draw more than the limit. And that's what capacitors tend to do when they're empty and suddenly attached to a power source capable of sourcing plenty of current.
That was interesting and good info to store away in the memory bank (bit). I'd have lost big money (up to 50 cents) if I'd been betting on the standby switch being useful or not. I wouldn't mind having a Tek scope like that one. (see note in parenthesis :o) ) 73 NE5U Mike
Yes, I agree. The scope is nice. There is a huge learning curve to operating it. All Windows 7 based. The current probe is really nice. The scope automatically sets its mode to current when connected. I had the scope to single sample mode. Thats why there was a delay as it was charting the trace.
I only use the standby switch when I turn the amp off so when it's turned on again too much current doesn't harm anything. Does that help in any way or am I off base with that concept?
I am new to tubes and I will never use my stand by on the mojo bassman ri.
My only other tube amp is a 6505. I wonder if it has the same problem.
The purpose of the standby switch is to make the amp dead quiet when the band is not actually performing, while leaving the tubes hot and ready to work immediately.
Also, guitars, mikes, and speakers should only be connected or disconnected when the amp is either fully off or is in standby mode. You risk damage to your equipment if you connect or disconnect while the amp is "live". The standby switch thus lets you keep the amp warm and ready to play while changing equipment around.
There is no problem about stressing the tubes by sudden surges. Before the solid state era, millions upon millions of hi-fi amps and TV sets were made, all tube in design but with silicon rectifiers after about 1958 or so. No degradation in tubes life was noticeable after the change to silicon rectifiers.
Switch-on surges in HT were a problem with high power tubes used in broadcast radio transmitters, but they used a different type of cathode, and the voltages were much higher.
There is a problem with leaving an amp in standby mode for long periods. When tube heaters are on without anode current, the cathode slowly develops what is called an "interface layer" - a high resistance layer between the cathode nickel sleeve and the oxide emission layer. This interface layer causes a reduction in tube gain. In Western tube manufacturing, this was prevented by using ultra high purity nickel for cathodes from the early 1950's onwards. However, Chinese made tubes that you buy today do not have the required high purity of nickel and the problem has returned.
The waveforms shown in this video are invalid - he's connected his probe at the wrong place, and is measuring the filer capacitor surge, not tube surge.
Your last paragraph should have been first.
@@MrJohnnyDistortion : Depends on whether you want to know the real purpose of standby mode, or you want to knock the D-Lab guy.
@@keithammleter3824
Nice disclaimer.😂HE'S SAFE, HES OUT! Pick one that suits.😃
So then you are saying it's not a problem to turn the amp on in standby only to leave it on standby for long periods. If that's the case, wouldn't it be better to get into the habit of not using stand-by and turn the amp volume to zero instead? Is there a problem with turning the amp on with stand by off? And what about potential arcing issues?
@@JimmyDevere : Correct - the risk is only in leaving an amp in standby for long periods. There is no problem in turning an amp on in standby mode so that it warms up mute. Rotating volume and tone controls causes wear, leading to scratching noises and intermittent loss of volume while playing. Therefore, only rotate volume and controls when necessary for artistic purposes - do not use volume control to mute an amp. No problem with tube interface layer degradation would occur over long periods by turning the volume down instead, but if you know its going to be a long period, you can turn the amp off completely.
I'm not sure what you mean by arcing issues. Amplifier output tubes, output transformers, and tube sockets can arc over if the amp is on, not in standby mode, and speakers are disconnected. Good quality amps eg Fender use a very small amount of negative feedback to minimise this problem, which can arise if your speaker fails by going open circuit while playing. But don't rely on this feature.
Let me know if I am wrong but if it's solid-state rectification I always use the standby switch and if it's tube rectification I do not use the standby switch as it's the perfect soft start...
But is a current spike really something to worry about with valves being inherently high impedance devices?
What about cathode stripping / poisoning when a high voltage is applied to a valve that is not warmed up? Is that not an issue in your view?
Cathode poisoning happens with tubes in standby for long periods. Cathode stripping occurs in tubes running over 1000 volts. In other words, standby switches are useless and hurt your tubes.
Yeah its a Mute Switch for most guitar players , you don't want to mess with your Master Vol once you got it in the sweet spot.
That's gonna end up being a costly way just to mute an amp. A simple switch between the signal chain and ground would work better, cost less, be safer and not have negative effects on other parts of the amp. Also the guitar has volume knob lol
I use the standby switch when I play live, between sets. It takes too long to get sound when I first turn on the amplifier otherwise.
The diodes get hit hard either way. I was thinking if a thermistor installed between the power switch and primary lead would help save the diodes from the inrush? Any thoughts?
I think guitologist did that very thing with a thermistor on one of his videos.
The reason why Leo Fender added a standby on the Fender Bassman was because it had a cathode follower circuit (which Marshall amps copied. A cathode follower can ark without a standby switch. The cathode needs to remain within a range of voltage relative to the heaters. Simple circuitry can be added to prevent this kind of arching, that negates the need for a standby switch. Some circuits do need a standby switch in order to function correctly. For instance, various oscillator circuits need it in order for capacitors to charge correctly, however these kind of circuits are rarely used in guitar amps, and have since been replaced by semiconductor circuitry.
Alva Goldbook you can easily avoid this issue by simply placing a neon bulb between the control grid and the cathode tho. They say it was for tech-manteining purposes... And I've read a lot of other theories about that. Personally I think that them are all true, for a reason or another. There are a LOOOT of good reasons for a manufacturer to install such device, but for the purposes if the user... meh.....
Good watching as usual, regards Les G4XMX yet again
Can't remember about turning on, but if I turn my JMP 2203 off with the standby on it makes a popping sound so for that reason I will turn the standby off first.
That popping sound is the power supply capacitors discharging, which is a good thing.
Cheers,
Alan Tomlinson
The standby switch is heritage of the old technique from high power radio transmitters. Leo Fender was a radio service man before he started to make beautifull things. With this background he puts standby switches in his amps. Allmost every ampbuilder in the '50's copied the Fender Basman, with all his mistakes. Look at the tonestack, a very poor design, is still frequently used. When you look at the normal use of the tubeamps in the past, in receivers for instance, you see never a standby switch.
chippster stephens
Amen, Brother !
I would have thought that even in a solid state rectified amp with a simple on/off switch and no standby, powered on from dead cold, would have been smooth power up just for the fact it takes the heaters a while to warm up
I have done a video on this as well with a slightly different perspective with silicon diode rectification ruclips.net/video/zxT1r51SZuI/видео.html
I don't know, standby seems really important. Not using it could maybe possibly potentially cause cathode stripping if you regularly turn your amp on and off in sub-arctic temperatures.
Although to be fair your tubes would still outlive you in those temperatures.
No. This is simply wrong.
Thanks for the video. I have a Vox AC-15 and the instruction manual specifically tells users to keep standby off and allow the tubes to warm up for a few minutes before flicking it on. Do you know if this amp has a different design that necessitates this, or are the instructions just a relic of the old myth?
I want to know the answer to this exact question. I've been doing as the manual instructed without fail for five years. I just recently replaced my tubes and I would like them to last as long as they can.
@@seanmcaleavy2369 tubes aren't as fragile as people have been lead to believe. Most of the myth surrounding it actually came from setups using MUCH higher voltage, where sometimes it did matter. You wont notice your tubes going out any quicker if you dont use your standby. Tube amps dont run that high of voltage for it to be noticable. Plus, nothing beats a fresh set of tubes. And yes I'm speaking from my personal experiences. Have fun and play loud
@@michaelsorenson3887 Thanks, I appreciate the info.
By the way thanks for
The video on cause
And effect in the P/S
Out put tubes and rectifier when toggling
The standby sw.
So I should use the switch or no?
So the standby switch when in standby on allows the filaments to stay heated, but keeps the high voltage off the plates, then when standby is flipped off high voltage then hits the plates and the amp is ready to amplify correct? I was under the impression one should put their amps standby on, then turn on main power switch to get the heaters glowing for about 30 seconds to warm up, plug in the guitar and then flip standby off and play, correct?
If a break in music is then needed, flip standby back on, come back, flip standby off and continue playing. Am I understanding this all correctly?
Thanks
That's what I have always done except leave the standby off then turn power off to discharge the caps. Reading through these comments it's hard to figure out who's correct.
@@JimmyDevere Makes sense to me to what you do, the high voltage will typically bleed off through warm tubes after you kill the main power switch I was told.
@@repairfreak When you switch off the amp, the tubes continue to conduct as their cathodes cool down, draining the high voltage. (If their is a standby switch it must be in the 'play' position.)
Nice demo, Terry. Couldn't the 'cushioning' effect of the tube rectifier you described be adequately performed by placing a thermistor in series in the power supply for a slower build-up of juice?
Hello, I believe so, however it may dampen the quick note attack that Marshall players love? not sure
I gotta have my quick note attack. ☺
You cork sniffers are driving me bonkers! Im starting to think nothing is made right unless you make it. 🧐
Good stuff
Good man, i like this video
So, kind of unrelated but is there a reason to let amp sit after playing for a while on standby before turning it off? I ask this because I am terrible about forgetting to turn them off after this step! Just the other day I noticed I had left my old blues deville on standby for 4 and a half days! Did the same thing with 2 twin reverbs once before. How bad is this and what parts am I shortening the lifespan of? Just power tubes or more? Thanks to anyone who can tell me more lol.
There is no reason to let an amp sit on standby. Simply turn off both switches at once. Letting an amp sit on standby for long periods of time (e.g., four and a half days) can result in cathode poisoning which degrades the performance of all the tubes.
Thanks, Terry
I would be interested to see the test of the marshall with a resistor across the standby switch like some people suggest. I guess the idea is that it would lower the voltage that gets switched on. Do you have any thoughts on that?
Hello, I have not heard of that mod. Will have to check it out.
ceriatone has it with a cap on their bassman layout. the valvewizard mentions it on his page about standby switches.
I was wondering the same thing, I use a this in a couple amps. One with diode rectification and the other with a gz34. I always put the standby switch after the first filter cap and an appropriate resistor across the switch. Makes for a 'softer' start with less of a current jump. Seems to cure the dredded standby pop sound too.
The standby switch is pretty useful in my prosonic while in class a!!! Mannnnn those 6l6 and output trans get hot while "idling" !!!
So to make the ending of this video more clear, you will get a spike with or without the standby switch on a solid state rectified amp like a Marshall. You will have a slow turn on with tube rectified amps with slow turn on like some Fenders and Vox AC-30s. Personally, if an amp has standby, I'm using it as I always have and never had issues. The standby debate is silly. This debate only came around the past few years, but these amps have been around for over 60 years.
Whether wrong or right, better or worse, I’ve been using standby switches for over 35 years without issue. I have one amp that’s tube rectified that I got recently so I think I’ll actually not use standby on that as my history/experience is pretty much Marshall based, SS rectification.
Im so glad I moved on past Tube amps. Way too much mainteneace, too much stress, too much sensitivity to current fluctuations etc etc etc. I have a "middle of the road solid state" going into a Seismic audio cab with DV77, Swampthang, Manowa5r sheffield speakers & I need No pedals, No boosts, heavy & huge tone & articulate , just love it & the clean channel is full & pure clean. Pickups are S,.D Nazgul & Sentient. I leave the tube amps to the others , Best tione Ive ever had and basically no maintenance .
But what about electron stripping! The bane of all tube amps! lol that is the general comment I hear when this comes up. I think that only happens in very high voltage systems (say 1kv+) and that is like so far above where an amp runs that there is zero chance of that occurring.
Dimebag Dio Kilmister that's more a feature of very high output tubes such as used in radio transmitters, where anode voltages are in the kilovolt range.
It's a common problem in cathode follower circuits, but it tends to happen slowly over time. It's easily remedied by replacing pre-amp tubes periodically.
It also only happens on REALLY high voltage setups. Standard amps won't have an issue.
Generally speaking, the cathode must remain within a voltage range relative to the heater. For most 12AX7s, this is about 180 volts. But damage over time can happen at lower voltages, and so it's important for amp builders to design around this issue.
Alva Goldbook
Love The 12AX7 ! ! !
Um... I thought the standby let the tubes warm up a bit before being hit hard cold. It allows the internal frame to expand evenly.
I always thought the standby was more for the filiments than plate current.
Great explanation, and proof is on the scope! So Terry, if I may ask...on my mid 80's JCM900 high gain dual reverb Mod. 4500 50 watt head/EL34's just turn the volume down upon start up, let warm up, don't worry about the standby? When taking a break, just turn down the volume and all good? If I take a 10min break should I use the standby, or again just bring the volume to 0? Waving a hand in Jackson. Love your 'vid's'....all the best around the ponderosa. ")
I'm pretty sure its had EL34's from the factory. It was serviced by a guy called Dr. Zink before, I guess he's a pretty good amp tech. It sounds just great, but I think EL34's are getting hard to get? Maybe I should have the conversion done. (thanks for the reply).
Jeff..I think its original? The amp is a 1991, and has a sticker inside with the date of service by a tech named Dr. Zink.
How does a Mesa compare? Would it be the same as the Marshall test?
Hello, Have not tested the Mesa line yet
My stand by is used only when starting up my amp after that it’s just on AND off till I’m done
the main point of a standby switch isn't maximum current draw at start up but cathode stripping as a function of the power tubes (and even the preamp tubes) if they're powered up before the heaters have a chance to stabilize....a tube rectifiers won't put DC on the plates before it's heater has a chance to come up. Ideally in the same time period as the other tubes. Most tubes with an "A" suffix have controlled heater characteristics that allow the heaters to come up in roughly 11 seconds. So in practice a standby interval is all that's necessary for SS rectified amps and none for tube rectified amps.
CSGuitars explains why you shouldn't use your standby switch in his video, and he talks about cathcode stripping.
Wasn't expecting that much difference
Very informative, what about the vox ac30cch standby switch, use or not to use?
I have an 1980 Fender 75w Lead amp with 6L6GC output tubes and a solid state rectifier. It has a standby switch, that I have always used (im
I'm the original owner of the amp). I'm also an electronics technician who repairs his own amplifiers and other gear, and I appreciate knowing that I'm better off not using the standby switch, but just leave it on all the time. Thanks for the heads up!
what about shutting off?
I always turn the standby switch on because I'm afraid of the pops. Then you get the pops anyways. The longer you warm up it seems there is less of a pop. But a pop none the same. Scope dont lie though.
I was under the impression that the standby function spared the filter caps from a spike by allowing the tubes to warm up. Anything to that?
Hello, on Marshall amps, the AC feeding the diode rectifiers are switched by the standby SW, therefore the filter caps see no HV until standby is set to ON. On Fenders, They switch on the rectified HV after the rectifier tube, caps are already charged. It really depends on how the manufacturer decide to insert the function. The filter caps have no issue with a few millisecond surge, especially after a tube rectifier since it has natural sag. Hope this helps. TD
Thanks for clearing up my misconception.
very good, at least one guy busting the stupid myth, McIntosh never used a standby in their 350W amps, so why bother,all you need in a ss rectified amp is a current limiter and you're done.
Because Solid State is the problem.
Point to Point is the only way to go.
The problems with Solid State are the Printed Circuit Boards. They just create their own problems. They can't stand up to usage, which is why they are Throw Away Units.
i.e., mars hell !
You might want to check electrolytic capacitors voltage when amp is cold and your turn it on with stand by on operation setting
We always joked with cooking sausages on the plexi hot tubes after playing for a few hours lol
If there is no input signal, that amp is essentially at idle
Learn something every day.
Thermionic valve technology is 120+yrs old.In 1906 Lee DeForrest invented the audion valve.The first audio output tube.Thanks Lee!
Dsl 100 and 1990 infinium both make a pop if you turn it off with standby on
I made 2 different amps outa silvertone hifis and they dont have standby switches
On my Peavey, the standby switch is located between the solid state rectifier and the filtering capacitors. The initial current rush can be caused maybe more by the caps than the tubes?
My apologies for being an absolute idiot but....... on my Peavey 30, do keep the Standby in OFF or ON position when turning the amp on? I think what has me confused is that the word STANDBY means something to me that is of little value in the amp world. BTW, your channel is just the best.
Thank you so much, 😊♥️
I leave my tube amps on for days at a time. Never had an issue. Only shocks affect them. They are meant to stay energized.