I recently bought a 1970 Fender twin with a busted standby switch. Now I've heard that one should never use a tube amp with a faulty ss because of damage it might do to the tubes. However, I recently have been reading the opposite from a variety of technical and professional sources. Just wanted to know what you folks think.

If you go from a cold start to fully 'on' with a valve/tube amp (as in, missing out the in-between 'standby stage'), there'll be no adverse effects...at first. It might not sound as good as normal initially, but iirc the reason why we're advised to use the standby stage is to allow the valves/tubes to warm up adequately prior to use. Repeated 'cold starts' will shorten their life and you'll find yourself replacing them more often. It's inconvenience and expense that can be lessened by instead spending a minute or two of time whenever you use your amp.

What exactly is wrong with the standby switch BTW? Does it allow the amp to work at all? I wouldn't use ANY amp unless both power switches (on/off and the standby) were working properly. If an important switch is broken, there could be worse issues to worry about than cold valves. Even small amps can have huge voltages and currents running through their circuitry, and a Twin is by no means a small amp!

I'd strongly advise getting that switch fixed, most importantly for your safety but also for the safety of a really nice amp.

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Guitar rig: CIJ Fender Jazzmaster/CIJ Fender Mustang -> TU-3 -> RV-5 -> OD-3 -> custom IC Muff -> PS-2 -> DD-3 -> RE-20 -> LS-2 -> Fender '65 DRRI & Mesa/Boogie F-50

Bass rig: Fender MIM Jazz Bass -> TU-2 -> RAT 2 -> Sansamp BDDI -> RV-3

"...So now you know the true secret to great tone: all the espresso you can handle."

If your amp has a solid state rectifier and properly spec'ed capacitors (early Fenders didn't) then a standby switch is not required for warm up on start-up. Many amps didn't have them. I have also heard that they exist so the amp is spared the stress of a restart between set breaks.

I personally believe they are a hold over from the radio days (Tube amps all started as radio amps (i.e. from circuits published in radio journals)). In a radio transmitter powering down the output stage was an actual requirement when not tranmitting.

Still an area of enormous contraversy. It would be interesting to have a definitive answer from actual experts, preferably ones who worked in the industry in the 50s.

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Thanks guys. The reason I questioned this in the first place is mainly because of an article I read by Merlin Blencowe from his book of amp design. That got me searching even more. I will certainly get the switch replaced but it got my curiousity going. And apparently my amp does have a solid state rectifier too. Just wanted to hear from others. Thanks.

Trust me.
Merlin KNOWS what he is talking about.
There is NO need for a SB Switch on a guitar amp. There never has been, and there never will be.
Cathode stripping is an Internet Myth, along with many other "facts". It continues to make me chuckle that people think you will somehow "damage" a guitar amp by simply turning it On, or even by leaving it On.
Some amps (Vox AC30CC) are indeed damaged by the USE of an SB Switch.
If you are not savvy, I would definitely take it to a tech to get that looked at, and make sure there are no peripheral troubles.
Once your amp is functioning correctly, you can just leave that SB in the Off position, and turn the amp On and Off with the Power Switch (there is a novel idea).
best

I'm not directly refuting what's being said in this thread - there's some really interesting info that I hadn't heard before - but why do the instruction manuals recommend putting the amp on standby before fully switching it on? The exact time varies - Mesa say a minute and Marshall say two to three for example - but EVERY valve amp I've owned, without exception, suggests you do this. I see no reason for them all to lie or all to be mistaken. They're the ones who are physically designing and building the things, so without a shred of sarcasm or bitchiness I ask: what's going on here?

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Guitar rig: CIJ Fender Jazzmaster/CIJ Fender Mustang -> TU-3 -> RV-5 -> OD-3 -> custom IC Muff -> PS-2 -> DD-3 -> RE-20 -> LS-2 -> Fender '65 DRRI & Mesa/Boogie F-50

Bass rig: Fender MIM Jazz Bass -> TU-2 -> RAT 2 -> Sansamp BDDI -> RV-3

"...So now you know the true secret to great tone: all the espresso you can handle."

They "designed" what.?
You need a lesson in guitar amp history, amp plagiarism, and the RCA manual. You are looking/seeing a history of direct copying of circuits from one amp company to the next..... INCLUDING mistakes. Ever wonder why the Tweed Deluxe or AC15 have those funky/stupid tone stacks.? Sure, they are cool now because we are use to them. But they are both mistakes from copy issues.
Ask yourself why/what the SB Switch does. Better yet, ask Randall Smith. Then ask him where he would be without the Fender Bassman/Twin.
Other than mass produced amps from BIG companies, I have never seen an amp manual. You gotta remember that the "engineers" that work for Vox, Fender, Marshall, Crate, etc. etc. etc. very well may have been "designing" toasters at their last job.
Then there is YOU. You are the classic example of why these big companies install an SB Switch. Their customers expect it.
Should I keep going, and discuss the iffy quality of the Elytic power supply caps that were available 50 years ago.
Use the thing if you want. With a few exceptions (like the vox) most circuits do not hazard from the switch. But I guarantee you.....there is NO evidence of a guitar amp EVER being damaged from the lack of an SB Switch.
Good Luck

*sigh* I kinda expected this response. So yeah. So here's the situation: I have, on one side, fellow musicians/amp owners whose opinions I trust saying "SB switches are pointless." On the other, the instruction manual that states that the switch is necessary for it to work reliably.

I'm not being an argumentative ass (I would've thought you guys would know me better than that, honestly). So, when I read something like this:
I hope you can understand why I asked, "whut?"

I'm glad you mentioned Randall Smith by name, because the quote above comes from the manual for my own Mesa amp. I'm not denying you know what you're talking about, but I genuinely don't know what to think. Really. I know about how Marshalls came from hot-rodded Bassman circuits, the first Boogies were based on Princetons but quite honestly, no I'm not an electrical engineer. I'm simply an educated adult who has to admit that the people who build something are likely to know more about it than I do. Does that in itself make me stupid and ignorant?

I'm sorry if I rubbed you up the wrong way and I'm sorry if I'm inadvertantly coming across as confrontational, but I hope you can understand why this whole issue is leaving me scratching my head...and why I'm starting to feel somewhat insulted for actually paying attention to the instructions that come with the (complex and expensive) equipment I use.

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Guitar rig: CIJ Fender Jazzmaster/CIJ Fender Mustang -> TU-3 -> RV-5 -> OD-3 -> custom IC Muff -> PS-2 -> DD-3 -> RE-20 -> LS-2 -> Fender '65 DRRI & Mesa/Boogie F-50

Bass rig: Fender MIM Jazz Bass -> TU-2 -> RAT 2 -> Sansamp BDDI -> RV-3

"...So now you know the true secret to great tone: all the espresso you can handle."

You are coming across as a well mannered, educated, wanting to know WTF is going on musician. I understand your confusion. The manual for the amp that you bought says to use the SB Switch.
Some guy (me) on the Internet says you do not need to.
Trust me. I would never tell a guy to do something that would hurt, ruin, damage his amp. They are a passion with me. I build and repair them as a hobby. Some musicians even have enough money left over (after drugs and rent) to actually pay me.
This is an ongoing and confusing topic. It gets real hard, on a forum (unless you are a writer) to thoroughly explain all this stuff.
If it makes you uncomfortable to NOT use the SB.....by all means USE it. I am just saying there is no technical reason to use it, and there is NO proof that lack of an SB damages a guitar amp.
The Power Switch is the one that can really stress the tubes. It runs the heaters. But whatever.
NONE of this is worth loosing sleep over. If your tubes go 1000 hours instead of 1150.....who cares.?
Turn your amp on..... 20 seconds will allow ANY poorly designed bias circuit to catch up, then hit your SB Switch. NOBODY needs to wait any longer than that.
Concentrate on your playing and forget we even had this conversation.
Good Luck

Many people at the Ampage forums claim standby switches are glorified mutes, and as much as they may extend the tubes' life it will probably do it in the seconds or minutes range. I like them because they keep the amp warm between sets, and I use them somewhat supersticiously: I've seen so many people use them that I don't see the reason not to.

On a side note, on the same Ampage forums I read those switches can actually harm an AC30 (or was it the AC15), but they didn't say why or how.

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Selling BOSS FW-3. I live in Brazil, mind you, so prepare yourself for $30-ish for shipping and waiting. Local pickup available, along with beautiful beaches and cheap bitches.

I'm thinking about an AC30, so how do you prevent the damage, constantly leaving the standby in the position that doesn't mute?

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Talking about wireless pedals...

Depends which AC30.
If it were me, I would just always leave the SB in the Off position. Just pretend it is not there.
I have an AC30CC. These are the amps that had a HUGE issue with the SB. It was always blowing the rectifier tube. I just hard wired mine in the Off position. Vox solved the problem in the next model (AC30C) by going with a solid state rectifier. Players could then flip the SB all night long and not have a problem.
If you are buying a CC You should either switch to a Weber Copper Cap, or just leave the SB in the Off slot.
best

Ah, I see. Thanks for being so understanding. I've seen so many discussions blow up purely on nuances of emphasis that are lost when typing online. I must admit I've wondered why most valve amp have SB switches while quite a few don't so the doubt has been nagging at me for quite a while. Why do so many manufacturers - even 'contemporary' models from Mesa and Blackstar, as well as reissues of old designs from Marshall and Fender - go to the time and expense of fitting a non-essetial component that just adds one more thing to potentially go wrong (as happened in the OP's case)? I guess we'll never know. Small wonder then that it's caused so much confusion and controversy!

No hard feelings then...I've fortunately spent the whole weekend in Germany drinking beer in the sunshine, so I'm definitely not upset about this discussion - or anything else - right now!

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Guitar rig: CIJ Fender Jazzmaster/CIJ Fender Mustang -> TU-3 -> RV-5 -> OD-3 -> custom IC Muff -> PS-2 -> DD-3 -> RE-20 -> LS-2 -> Fender '65 DRRI & Mesa/Boogie F-50

Bass rig: Fender MIM Jazz Bass -> TU-2 -> RAT 2 -> Sansamp BDDI -> RV-3

"...So now you know the true secret to great tone: all the espresso you can handle."

IMHO...all the standby switch does is allow the heaters to warm up before turning on the HV B+. It's more of a ritual. I turn the power on and then the standby a few seconds later. During set breaks I put the amp in standby. It is effectively a mute, like was mentioned before, but you also do not have to wait for the amp to warm up again when you start the next set. I doubt that not using the standby switch will make much operational difference in your amp. I would be more concerned that the switch may be resistive and carbon arced in the closed position. That definitely could affect your amp and could also be a safety issue. Btw, if you want to see a wierd stand by circuit, look at a Silvertone 1484!

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Stage Guitars: '80s Thin line LP Custom, '70 LP Standard, '83 Squier Black Headstock Strat w/ Dan Torres pickups, '59 Black Danelectro DC, sometimes others.

Pedal Board: Nady UHF 10 -> TU2 -> Rocktron Big Crush -> 70s MXR Phase 100 -> Cry Baby -> Bad Monkey -> Early '80s Rat -> Early '80s Ibanez CS 9 -> Ibanez DE 7 -> Behringer Dr 100 Stereo Reverb

Stage amps: '63 Blonde Tremolux w/ two original 2X10 cabinets with a '60 Ampeg Rocket/18 watt VTB Marshall clone/ Epi VJ into a Mashall 1965A

Never seen that 1484 circuit.
I suppose it is a phase cancellation inject. The power tubes get a net signal of Zero and so put out Zero signal to the OT.
Very interesting. Thanks for the shout.
I guess both the B+ and the heaters just keep doing their thing while the SB is on.
Talk about "More than one way to skin a cat" !