To stand-by, or to not stand-by?

[MWJB]

Jared "Best of luck. As a newbie, I actually think that I might be further along than you!"

Jeez...and you called me arrogant? I can assure you that you are not further along than Tom, who is a knowledgeable, regular and respected contributor to this forum, his opinion is worth listening to. You are a nightmare Jared, you have bought an amp that has an issue, you have raised this issue with Mesa, the tech at the store, the manager of the store, in 2 other threads on this forum, on another forum and are constantly pitting opinions from one source against another. Ultimately, you have no intention of resolving the issue with the amp yourself (in terms of tangibly rectifying the issue at hand), you are protected by warranty & whatever the Canadian sale of goods act is, yet you aren't doing anything about that. You haven't even grasped the issue with the amp that you have, if you had, this thread wouldn't exist (the problem isn't your standby switch, as you have been told several times). It just seems to me that you just want to make as much noise as possible, because you have spent what you see as a lot of money and you're not happy. I wouldn't be happy either in your shoes, but if you want something actually done about it go back to the store...no-one on this forum or any other is going to solve it for you because it involves actually having your amp, opening it up & putting a meter on it - something that should be done under warranty by the vendor, or manufacturer (I have said this before too, I wonder how much you actually read of your own threads), no matter how much anyone types on to a forum thread it's not going to change the perameters in your amp because your amp can't read them & fix itself.

Time to shit, or get off the pot. Go back to the store & get your money back, nobody put a gun to your head & made you buy the LSS, the C30, or the PRRI, take responsibility for your own actions. Or, google some of the points raised in these threads (start with "tube idle current"), or buy some literature on guitar amps, so that you can form your own opinions, rather than "play both ends against the middle" with other peoples (with which you never seem to be happy).

[redelephant]

A thermistor is a great idea. I also use them on the heaters to limit the inrush current on cold cathodes (which I've measured to hit 1amp on preamp tubes! That's more than 3 times the standing (warmed up) current!)

I don't get the personal slandering going on here. Jared may have got an answer regarding his Mesa amp in a previous thread, but this thread was about standby switches in general wasn't it? No probs if he uses his Mesa as reference since that's the amp he has issues with. Besides, with all the different 'facts' coming to the table by different people, it's obviously a confusing problem.

I must admit I haven't bothered reading the posts longer than two lines where personal slanderings are included, so perhaps I'm wrong, but I see nothing wrong about this thread.

I did some 'serious' (well, at least time comsuming) reading on the subject some years ago. My advice is go to Pete Millet's website and download some books, mainly 'Getting the Most Out of Vacuum Tubes' by Robert Tomer. Seriously folks, this is not black magic, (tho it may be a lost art), all the know-how is available. A thorogh understanding of Kirschoff's and Ohm's laws, and a decent understanding of physics is all ya need, plus some of those books.

As I mentioned the tubes with the longest recorded life are the ones that are never turned off. I have some prototype amps I've leave on for about 90% of the year. I only turn them off when away for more than a few days. And they have never had tube issues, and the same tubes are still there, never a tube change. One of them is at least 8 years old.

I agree with 'ThermionicScott'. Find the noisiest position and leave it there. My advice to my customers is if a pause is longer than one hour, turn it off, otherwise leave it on.

But for warranty issues, the best is probably to follow manufacturer's recommendations, though I'd be arrogant enough to say many manufacturers don't know what they are talking about

[DumbGuitarPlayer]

Forgive me if I missed it, but I didn't see where anyone mentioned the use of a standby switch to protect a tube in a cathode follower stage from destructing when the grid gets pulled up to the B+ before the cathode warms up. It can still happen with a standby switch used to warm the tube up, but it's a definite concern when the B+ is applied to cold tubes.

[redelephant]

So? Does that cathode follower suddenly conduct much earlier than the other tubes? Even if it does, it can handle it.

[DumbGuitarPlayer]

So explain to me how the grid getting pulled to B+ while the cathode is at ground potential is not a concern?

[Steve Conner]

Well, where does it say in the tube datasheet that you're not allowed to do it?

[redelephant]

So explain to me how the grid getting pulled to B+ while the cathode is at ground potential is not a concern?

Sure. Lets say the grid is pulled to 300volts and the cathode sits at ground since it is cold. There is no free electrons yet that can go to the grid, so no harm done. If by chance the cathode follower warms up first and starts to conduct before the common cathode stage it is directly couple to then it will at most act like a diode and conduct whatever in the short time it takes for the plate voltage on the preceding stage to get down. Perhaps it conducts a whopping 3mA instead of the 1-2mA during normal operation, or even 10mA instead of 3mA, big deal. You have both a resistance in series with the grid, the plate resistor, and the cathode resistor.

If you have a design where you have issues like this that may give a potential for worries, well, why not use the standby switch as normal? If you know a reason to warm up the tubes, then do so. Don't worry, be happy I still say it's there to protect lowly rated caps, and as a mute function.

I just did some simulations on PSU designer (available from duncanamps.com) and in a typical power supply setup with tube rectumfriers, CLC (15uF-5H-15uF), I get 600volts without load (cold tubes) and 500volts with 75mA load (warm tubes). That's a whole 100volts that can ruin a 500volt rated cap any day.

[DumbGuitarPlayer]

Um, grid-cathode arcing? Come on now.

[DumbGuitarPlayer]

To clarify I am talking about DC coupled CF arrangements. You get a grid (physically close to your cathode) that goes WAYYYYYYYYY positive because it's tied to the previous stage's anode. All the while the cathode is still at ground potential. Well now you have two electrodes close together that are at significant enough opposite potential to cause an arc.

[Steve Conner]

Sure, but the electrodes are cold and in a vacuum, so there won't be an arc.

Don't get confused with the heater-cathode insulation. That limit applies under operating conditions where the insulation is at a bright orange heat, hence any ions in it are mobile and will cause breakdown over time. (The heater-cathode insulation is probably much stronger when cold, too.)

[redelephant]

If we were at 1kV and more I'd agree to be a bit concerned, but not at 4-500volts. (Which is why I included a 'at the voltages used for guitar amps' in my first post on this thread, to cover my beehind).

Anyhow, like I said, you are free to use the standby as you wish, I still say it's just a handy mute function.

[Prairie Dawg]

You are correct, oh pachydermous one. As I understand it the longest lived incandescent light bulb lives in a firehouse in Livermore, California-it has been running continuously since 1901 and aside from 2 or 3 shutdowns for power failures and moving, it has been going strong ever since. It's nothing but a vacuum tube.

I really do not get why more people don't use thermistors if they're worried about this stuff. They're cheap, effective, and there's little if any downside that I can see.

My old man often remarked that i was studying for my PhD in obsolete technology-he was a retired metallurgical engineer-but I always have thought that progress is a good thing but it's gone too far.

I don't get the crossed swords either-life's too short for anything but good tone and it's our job to find it wherever it may be lurking.

A thermistor is a great idea. I also use them on the heaters to limit the inrush current on cold cathodes (which I've measured to hit 1amp on preamp tubes! That's more than 3 times the standing (warmed up) current!)

I don't get the personal slandering going on here. Jared may have got an answer regarding his Mesa amp in a previous thread, but this thread was about standby switches in general wasn't it? No probs if he uses his Mesa as reference since that's the amp he has issues with. Besides, with all the different 'facts' coming to the table by different people, it's obviously a confusing problem.

I must admit I haven't bothered reading the posts longer than two lines where personal slanderings are included, so perhaps I'm wrong, but I see nothing wrong about this thread.

I did some 'serious' (well, at least time comsuming) reading on the subject some years ago. My advice is go to Pete Millet's website and download some books, mainly 'Getting the Most Out of Vacuum Tubes' by Robert Tomer. Seriously folks, this is not black magic, (tho it may be a lost art), all the know-how is available. A thorogh understanding of Kirschoff's and Ohm's laws, and a decent understanding of physics is all ya need, plus some of those books.

As I mentioned the tubes with the longest recorded life are the ones that are never turned off. I have some prototype amps I've leave on for about 90% of the year. I only turn them off when away for more than a few days. And they have never had tube issues, and the same tubes are still there, never a tube change. One of them is at least 8 years old.

I agree with 'ThermionicScott'. Find the noisiest position and leave it there. My advice to my customers is if a pause is longer than one hour, turn it off, otherwise leave it on.

But for warranty issues, the best is probably to follow manufacturer's recommendations, though I'd be arrogant enough to say many manufacturers don't know what they are talking about

[Jared Purdy]

Yes. I did read the post. And the complete other thread about this amp.

Tom, my comment wasn't directed at you, sorry if there was a misunderstanding.

[GregS]

You are correct, oh pachydermous one. As I understand it the longest lived incandescent light bulb lives in a firehouse in Livermore, California-it has been running continuously since 1901 and aside from 2 or 3 shutdowns for power failures and moving, it has been going strong ever since. It's nothing but a vacuum tube.

My own observations with light bulbs around my house don't support this however. The best example is the outside lights on the house. I live in a place that has has a very cold winter where the thermal shock factor from turning off and on would be very big for 6 months of the year. Before I got motion sensor lights I was leaving these lights on all night and often part of the day as well. They were only lasting a few months and I was having to replace them constantly. Since I got the motion sensor lights the bulbs are now lasting for years. I have them set up so that once tripped the light stays on for 5 minutes before turning off again. The difference is that the lights are being turned off and on much more frequently but are not on nearly as much. They last much longer under these conditions than being left on a lot more with lot fewer turn on/turn off cycles. This is just observation.

With pre-amp tubes they'll last practically forever whether they're left on permanently or not as the currents are very low and don't stress them much. But power tubes???
This might be an extreme example but I've had an amp for coming up on 16 years that is still on it's first set of power tubes. It hasn't seen a ton of use obviously but has been turned on and off many times in it's lifetime. I seriously doubt the power tubes would still be good if I'd turned it on in 1995 and never turned it off again.

[Jared Purdy]

Jared, with all due respect, MWJB is a professional amp builder and long-term member (5 years? 10? As long as I can remember.) of the forum. You are... a guy who asks a LOT of annoying questions.

As you can see there is no real consensus amongst us on what the standby switch actually does, or is supposed to do. For all we know it may actually be a kind of self-destruct button whose sole purpose is to help Mesa sell more rectifier tubes. Why don't you call Mesa tech support and ask them.

I have to say, that I find a great deal of this thread to be really quite childish. There have been some excellent responses to a what I thought was a fairly simple question (and I thank those who simply stated what they thought with out getting emotionally involved in the answer): "To standby, or to not standby?". Seems innocouous enough. Clearly, that is not the case, but then I am not too suprised anymore at some of the comments that I read on these forums. Some people appear to be living in a parallel universe, where down is up and up is down. One poster replied, somewhat soberly, that we're not talking about nuclear reactors, or something like that. Right.

I posted the same question on two other sites, as is my common practice, and in not one instance was I accused of "asking alot of annoying questions", or of knowing the answer before the question was asked (which suggests that I have alterior motives for asking the question.). Pathetic. Truthfully, I find it somewhat ironic that the hyperbole around a very legitimate question, having accusations hurled at me, etc., came from this site, because I think it fair to say that the reputation that this site has/had, is one of a "higher level", owing to the technical questions and issues that are dealt with, as oppossed to some of the other somewhat banal questions and proclamations, such as: "NAD", or "what amp should I buy", or "show us your bedroom rig" type of questions.

There were some very interesting, and different replies on those other forums, with links sent to various sites that explain in detail, what some of you take for granted. The arrogance, and ivory tower mentality that is demonstrated when someone says that "I ask a lot annoying questions", unfortunately belittles this site, and is an attempt at stiffling meaningful inquirey. I have posted three threads on this site, with a total of three of four questions, that were related to two different issues, that I was trying to get clarification on. How that can be labelled as "a lot of annoying questions", I have no idea, other than higher than thou mentality.

As for the amp, I have no intentions of getting rid of it, and suggesting that it is a lemon because of a faulty tube is a bit like throwing the baby out with the bath water. Further, I'm surprised that the "high minded" here would utter such a ridiculous, and over generalization.

In closing, don't "waste your time" repsonding to this, because I am terminating my participation on this forum. I can particiapte on other forums, and ask as many questions as I like, as can others, without getting into this ridiculous and childish behaviour that appears to be so noticeable here. For those of you who are so busy, what the hell are you doing on this forum if your time is so precious? Don't you have to solve some major amp issues?