Standby sw necessary ?

[Colas LeGrippa]

Buenos dias amigos !


I am modifiing a Bogen CHB-50 for myself. All of the Bogen amps that I have seen don't have a sb switch.
Some techs think that sending high voltage to cold tubes may harm them. The first Bogen amp that I have modded, a CHB-20A, still had it's original power tubes and still HAS it's original power tubes....in perfect state of working order. Personnally, I have always put a sb sw in all my builds. In tube rectified amps, it seems different. By the time the rectifier warms up to produce HT, the other tubes are warm also.
What do you guys think ?


Colas LeGrippa

[HotBluePlates]

Did you do a search on "standby" on the forum? You might have gotten the answer quicker.

Standby necessary? No, you don't need a standby with typical guitar amp circuits.

If you want a standby, as a mute function, that's fine.

[sluckey]

In a guitar amp a STBY switch is a user convenience, not a tube protection device.

[Platefire]

Well on the side of a standby switch, you don't have to use it but if it's there and you need it, you have it!

[kagliostro]

Ditto


Franco

[Colas LeGrippa]

Ooops sorry guys, next time I will check in the archives before, I often forget to check there first ( I guess I am nissing some kind of human contact ! )

Have a nice day and thanxxx for your answers

Colas LeGrippa
 

[Platefire]

Yeah! Sometimes I'm just wanting to hear from you guys With all the raining/flooding thats been going on around here and cabin fever----Yall are a nice break!

[Colas LeGrippa]

YEP you got it: a nice break !

 Hey I got a song for you to sing if you got the blues:

..well it's floodin' down in Texas, all of the telephone lines are down...............

[Platefire]

Yeah, I got another line to add to that "Thank God I live on a Hill"!

[alerich]

I have stopped using my standby switches on my amps except during maintenance. I leave them on all the time. I like the thought that the still warm tubes drain the power supply before they cool.

[EKDENTON]

I just read some information from Gerald Webers book about whether your amp needs the stand by switch or not. The author states that there is a reason for the stand by switch, and although it also does work as a mute switch the other reason is that the vacuum tubes should be warm before high voltages are present. The stand by switch allows the tubes to warm up first. It's not necessary to have the stand by switch in any particular position when shutting down the amp but it should be in the stand by position when turning the amp on.

The author also says that if high voltage is present before the tubes are warmed up that "chemical coating" on the plates will begin to strip away. It doesn't say that the tubes will fail but that they will not "sound good" any more. (I have stand by switches on all mine so I have not tested what he has written, I am just passing on information from Gerald Weber's book).

The author also says there are some amps that do not have stand by switches. They do not need the stand by switch because they use "controlled" warm up tube rectifiers (GZ34 and the 5V4 are two such tubes) These rectifier tubes take longer to warm up than the rest of the tubes.   

The author says there are amps that are just bad designs that do not have the stand by switches. Two of these are the Orange and the Tweed Champ. The first has a SS rectifier and the second has a 5Y3. The 5Y3 has a directly heated cathode and produces high voltage almost immediately.

Just thought I would chime in with this info, many of the guys that posted above probably have as much or more experience with tube amps than Gerald Weber. I think that thread they said to check out was going on years back because I remember reading that the general consensus was that there is no damage to the power tubes without the switch. I always add them just in case. I figure a $4 switch is cheaper than a set of power tubes. I also always add the large resistor at the speaker jack just in case I forget to plug in the speaker to my amp. Guess I am just over cautious. LOL

[kagliostro]

The author says ........

a lot of things, but, believe it, you don't need it more than to use it as a mute

Franco

[alerich]

More authors takes on standby switches:

KoC:
http://www.londonpower.com/standby-switch

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

At least we're not debating the pros and cons of paper in oil standby switches.   

[Paul1453]

The author says ........

a lot of things, but, believe it, you don't need it more than to use it as a mute

Franco

Now this is what I believe too, Franco.   

I'm not sure about the tubes breaking down if left to sit with heaters on but no HV applied.   

But I figure, "Why take that chance with my old high quality tubes"?   

[HotBluePlates]

I just read some information from Gerald Webers book about whether your amp needs the stand by switch or not. ...

Merlin presents some counter-arguments re: standby switches on this page. [Alerich was faster]

I don't "have a dog in the fight." Standby or no, either way is fine by me.

The consensus we generally reached on this forum was that warnings of dire consequences if you don't have a standby switch are somewhat misapplied information from transmitting tube practice. That is, information which applied to transmitting tubes (and their very high supply voltages) was logically applied to receiving tubes (same class of tubes used in guitar amps) and their much lower supply voltages, but failed to recognize the lower-voltage environment doesn't present the same risks to the tubes.

So it's not critical to include a standby switch, though Weber's writing my lead you to conclude that. But it also won't harm anything if you choose to include one (I believe Merlin's warning about cathode interface is unlikely to manifest itself unless you leave an amp on but in standby for weeks on end).


I've been critical of Gerald Weber's books in the past. They helped me enormously when I didn't know anything and was starting to learn. However, once I did learn some fundamentals of electronics (away from an amp focus) and read some original sources on tube technology, I found Weber had some incomplete explanations, an occasional wild/baseless theory, and a heaping helping of marketing geared toward slavish copying of tweed designs & build process (naturally, because Weber sold exact tweed copies at the time).

Weber has a gift for conveying amp concepts to an audience with a limited technical background is a readable way. I recommend also referring to some old tube books as original sources for fact-checking as you get deeper into this stuff (a good idea for anything, really). And now, thanks to sites like Pete Millett's site, the old books are more readily available than they have been in the past few decades.

[EKDENTON]

Probably like you said Hotplate,  some of what Gerald has written.... he probably read from someone elses book or article and assumed that it also applied to tube amp tubes also.


 I really wasn't trying to play the devil's advocate....just throwing in something to talk about ;-)


Maybe there is some truth in the old saying "don't Believe anything you hear,  and only half of what you read". LOL

[kagliostro]

Is something that has to do with Radio Frequency apparatus

Franco

[darryl]

Maybe there is some truth in the old saying "don't Believe anything you hear,  and only half of what you read". LOL

...but you have to figure out which half to believe.

Like many other forum members, I'm old enough to remember the time before solid state came to dominate consumer electronics. Millions of domestic electronic devices used valves, with applied voltages similar to guitar amplifiers, and none had standby switches. Some used valve rectifiers, and some even used the new-fangled solid-state rectifiers, but still without standby switches.   

[PRR]

> domestic electronic devices .... none had standby switches.

Right.

Electronics roughly divides into low power and high power.

Most low-power stuff can be designed to be used by non-technical people who won't do elaborate start-up shut-down procedures. Oxide cathodes are tough to a point. 500V plates don't shed their surfaces. Tubes are designed and tested so abrupt turn-on/off does no significant harm. As most consumer devices are "receivers" (or similar like record players and small PA amps), these tubes are in the Receiving Tube Manual.

FWIW, most small transmitters use "receiving" tubes. 6V6 6L6 will do for police and taxi 2-way radio, which is good because policemen and taxi drivers are not trained electronics technicians.

Now when you have to transmit to 7 states, or harden cranks, you need BIG voltages and powers, KILO-watts. There is also some limit on physical size in radio transmitters. At this point the materials must be different and are likely highly-stressed. And costly! If function will be better with tight control of starting conditions, this is acceptable because they are worked by trained operators. These tubes are in the Transmitting Tubes catalog.

Even among "transmitting tubes", the advantages of consumer-grade casual operation are clear. 807 is listed in Transmitting, but can be cold-started as abruptly as a 6L6.

[Colas LeGrippa]

now I remember where I had read about HT applied to cold tubes: Gerald WEber , TUBE GUITAR AMPLIFIER ESSENTIALS .
Now that I am reading that book again, after 10 years or so in amplifiers tweaking and modding,,  I can see a couple of lacks in his theory too !
PRR, if you say so, I'll do so.

Colas LeGrippa

[Ed_Chambley]

We revisit this topic here and other forums all the time.  My take on it is if you think you need one, well by golly, you do.  If you don't think so then you don't.  I like it when they are included cause then I have a hole to use for a mod.


Thank you for your time and Good Day!

[Colas LeGrippa]

Yep....for the moment I don't know what to do.....

I am standing by

Is this my 1,500th post ????????????

[SoundmasterG]

Wow some of you guys post a lot more than me....I'm only up to 1038 it seems. :)


Greg

[Colas LeGrippa]

Yeah but have you seen HBP with over ten thou posts ?