Twisted idea for Standby Switch?

[sluckey]

The Standby switch for amps was a neat user feature when it first appeared in guitar amps. A picker could take a break and come back for the next set, flip one switch and kick off the next song. Or the rich picker could easily change guitars without a bunch of noises. Good stuff back in the '60s. But today it's not so clear cut. Lot of controversy about the dangers of a switch that has become kinda useless in the minds of so many. And don't forget about the crowd that believes it must be used with the power switch in a particular sequence to properly turn an amp on or off. I have my opinions about all this and most everybody else does too. I don't want to discuss the merits of a Standby switch. Rather, I want to throw out a crazy idea and get some opinions about the sanity of such an idea.

Here it is... How feasible is it to use a Standby switch to open/close the rectifier tube filament circuit? I'd like to hear what you think, even if it's just to say how stupid you are today.   

So, I'll start. OK, you will get a slow start that will minimize inrush cap charge current. Maybe OK for fast starters like 5Y3 or 5U4, but probably useless for a 5AR4 that takes 15-20 seconds to warm up. Sounds like a waste of a 1/2" hole to me.

Anybody?
 

[kagliostro]

Ciao Steve

I don't remember well, but initially on thr Valve Wizard page there was a standby that disconnected the heaters of the rectifier tube

later it disappeared and Merlin himself sometimes says that to disconnect the heaters is a good way to short the rectifier life

Franco

[shooter]

sound plausible, for the tube Rec crowd, but us SAND folk would just be wastin a switch 

[uki]

Robrobinette have some inrush mods in his page:

Standby Switch 'Pop Reduction' and Current Inrush Surge Protection  Every standby switch needs this resistor.

Add a Soft Start Inrush Current Limiter

[kagliostro]

Also Merlin suggests the use of a resistor in parallel with the Standby Switch

http://www.valvewizard.co.uk/standby.html

Franco

EDIT: I've just find this old patent, not very useful for us 

[JB]

I would guess the objection would be having HT on the rectifier anodes but a cold cathode which could lead to damage over time. How long that time would be and whether for practical purposes it matters I've no idea. 

[jjasilli]

I never met a standby switch I didn't like.  Though I'd like to think I'm open-minded.      I share the same basic concern with JB.


Would it harm the rectifier tube if it were subject to long-term full HT voltage, but no heater voltage?  .  My spider senses are detecting that there might be a problem, because no one is doing it. 

[shooter]

speaking of standby switch, EVERY standby switch in my career had a corresponding OPERATE position, why are musician switches exempt 

[dude]

So many amps from the sixties didn’t have a standby switch and I’ve never yet came across an old rectifier tube in one of those amps that was weak. IMO, for what it’s worth, not much  , you don’t need a standby. So, it takes 30 seconds, who cares. But for some season every amp I build has a standby,    unless it’s a conversion that doesn’t have a second hole. Cut the filament to rectifier, yeah go for it. Does it cause premature wear, six to one half a dozen to the other like 50% of all the questions asked here. Cheers,

[Colas LeGrippa]

I wouldn't fool around with heaters nor high voltage stand-by-me switches.  .


A much more efficient sb switch is on the other side of the amp: the signal.


A switch that  sends to gnd the guitar signal.


No filament, no hv, no short or long term harm.
All the inputs are sent to gnd when guitar cord is disconnected thus muting the amp. So a parallel switch doing the same is perfect.


Is there a disadvantage to leave on the high voltage during breaks ? No. Unless you play with redplating tubes !!!!








Colas

[tubeswell]

How feasible is it to use a Standby switch to open/close the rectifier tube filament circuit?

Without the filament heating up the cathode, there'd be no tube current in the rectifier and so there won't be any high tension voltage at the B+/cathode. The rectifier plates would be oscillating at high VAC, but this won't do anything.

Then you flick the filament current on and there'd be a surge of current through the low resistance of the cold filament (which won't result in any rectifier tube current yet because the filament is still too cold). So I don't see any problem there.

If it's an indirectly heated cathode, there's no VAC seen by the B+ reservoir cap until the cathode is hot enough to emit electrons (which takes a few seconds).

With a directly-heated cathode, while the filament heats up, there'd be a small window of time when the rectifier cathode/B+ is between 0 and 5VAC - before the B+ voltage rapidly increases. I doubt this would affect the integrity of the reservoir cap much, because by comparison, in tube-rectified amps where a standby switch is between the rectifier and the 1st filter cap, the rectifier plates and cathode would be at VAC when the mains power is on, and there'd be a (tiny) period of time after the standby switch is on (before the B+ voltage rapidly increases) where the reservoir cap is subject to between 0 and 5VAC. So this would be no different to having a directly-heated cathode sans filament current, then turning it on.

In short, I can't think of anything that is deeply flawed about this idea. But I may have missed something

[Ed_Chambley]

Why not just use the switch to ground the grid of v1?

[st]

I'm with Ed and Colas here. Sluckey, you list no other reasons for having a SB switch than being able to mute the amp anyway... Muting an amp by anything other than shunting signal to ground just seems bad engineering. Unless of course there is something else you want from this SB switch. Is there?

[sluckey]

I'm very aware of muting switches. I'm specifically interested in any comments concerning "How feasible is it to use a Standby switch to open/close the rectifier tube filament circuit?"

All the big tube amps in the '60s had a standby switch that killed the B+ (or B-). My twin twelve Silvertone actually used a mute switch to short the PI outputs together at the grids of the power tubes. Everyone I ever played with used the standby switches for their designed purpose. The only playing I do these days is in my shop so I don't have a use for a standby switch of any kind. However, I do find it handy and useful to be able to turn off B+ and leave the tubes and bias supply operating while an amp is on the bench.

[Colas LeGrippa]

From an electronic point of view, I can't give you the answer that only an engineer would give you. Kendricks says it is bad to send HV to a cold tube, The valve wizard says rectifier tubes don't like SB switches. I try to avoid abrupt changes in tubes conditions. I have in mind a red hot frying pan forgotten on the stove that you immerge in cold water. (GEE PUT ON ASBESTOS GLOVES !! ! )

[Colas LeGrippa]

......and get yourself a new one.

[DummyLoad]

why not just add a mute switch to the first stage? one could use a small toggle switch. less stress on PS components.


--pete

[sluckey]

I'm very aware of muting switches. I'm specifically interested in any comments concerning "How feasible is it to use a Standby switch to open/close the rectifier tube filament circuit?"

[DummyLoad]

I'm very aware of muting switches. I'm specifically interested in any comments concerning "How feasible is it to use a Standby switch to open/close the rectifier tube filament circuit?"

i'm sure you are. my way of discouraging that idea. sorry - not a fan of standby switches. as i stated - they stress PS components and are unnecessary.


--pete

[Platefire]

I been reading this but I'm a fan of muting and a fan of being able to cut DC to the rest of the amp when I want to. I think that's handy in trouble shooting. One thing about a standby switch is "you don't have to use it"!!!! When it's off, it's the same as if it didn't exist and if someday you wanted to use it, it's there. Lot of time jamming at the house with PA hooked up, wife's piano, JamMan(Band), my amp(with standby off)---when I turn on the power, I do it on the power block and turn everything on at the same time. That's how I see it. Regarding the rectifier/mute mod, why don't somebody try it and see what happens? Platefire   

[st]

ok . So now you (both Platefire and sluckey) expressed the desire to be able to shut off the ht for troubleshooting. You guys must get an awful lot of amps in with a problem in the filament supply, cause I have bever felt this need... But if it's only for troubleshooting, any switch (in the dc, ac sec, or rect filament) will be good enough. No tube will die from doing it once or twice on the bench. I know I keep hammering on the same nail, but while I don't think the idea is flawed at all (!), I think it's a solution to a problem that doesn't exist...

[jjasilli]

Is this a Rorschach test?    Virtually no one is addressing sluckey's actual question.  He couldn't have been more clear.

[st]

More than one person indicated that they don't (necessarily) see a problem in the proposed standby switch. That's a direct answer to the question. Several more have indicated they don't see the point. While that may not be an answer to the question, it's hardly irrelevant or off-topic. These answers are not contradictory; instead there seems to be a consensus that they proposed switch will work yet wmbe of little to no use. Do with that what you want.

[shooter]

Is this a Rorschach test?

whenever the academics' ask me to do these I get free services for a month   

[tubeswell]

I think all Rorschach tests look like animal pelts in various stages of decay, or squashed bugs. LoL

[jokn]

Since this thread is already out of hand, I figure I might as well throw this sort-of-related question/idea in: how about switching off power tube heaters while keeping the preamp ones live? Could be handy for home recording or going straight to the mixing desk live (provided the amp has a suitable output from the preamp). Good/ bad/meh?

[John]

I put a standby knob on all mine.


I label it Volume so the guitar player doesn't get confused. 

[Willabe]

I put a standby knob on all mine.

I label it Volume so the guitar player doesn't get confused. 

             

[shooter]

I label it Volume

 love it!
on some of my proto-builds I'd wire the 1knob TS backward and watch the confusion!