[Distroyed]

I've noticed some static coming from my right channel and confirmed it was from my right 12ax7 tube. I've had my MG Head DT/OTL on 24/7 for about a month now, and I pulled out the 12ax7's for inspection and noticed the glass was burnt at the top front of both. Only one is producing static. My question is if leaving it on for that long generally does damage tubes in the manner described or if this is just coincidence. Can someone who has left their tube amp on for at least as long as I have comment?

While I'm at it, does anyone know what the +/- switch on the power supply unit of the MG Head DT/OTL Mark II does? At which do I want it set?

 

[robm321]

Quote:

Originally Posted by Distroyed I've noticed some static coming from my right channel and confirmed it was from my right 12ax7 tube. I've had my MG Head DT/OTL on 24/7 for about a month now, and I pulled out the 12ax7's for inspection and noticed the glass was burnt at the top front of both. Only one is producing static. My question is if leaving it on for that long generally does damage tubes in the manner described or if this is just coincidence. Can someone who has left their tube amp on for at least as long as I have comment? While I'm at it, does anyone know what the +/- switch on the power supply unit of the MG Head DT/OTL Mark II does? At which do I want it set?

I never left my tubes going 24/7, but I had an issue with hum in one channel. I brought it in for repair and now it is silent. The MG head (older versions) have had these issues with them.

 

[braillediver]

The 12AX7 should have been good for several thousand hours- YMMV. That's dependant on the way the tube is used in the circuit.

There's an initial period where "infant mortality" is a concern like 0-300 hours and another as it ages 3000-5000 hours.

The times are generalizations. Otherwise chit happens.


There's really no need to leave the amp on full time- plus it's probably not safe to leave a tube amp on unattended (no one home) for any length of time.

I turn mine on and let it warm up for a half hour before using and turn it off when I leave the house. Tube amps can catch fire- heck anything electrical can catch fire if left on and unattended.


Mitch

 

[Labtek]

Quote:

Originally Posted by braillediver The 12AX7 should have been good for several thousand hours- YMMV. That's dependant on the way the tube is used in the circuit. There's an initial period where "infant mortality" is a concern like 0-300 hours and another as it ages 3000-5000 hours. The times are generalizations. Otherwise chit happens. There's really no need to leave the amp on full time- plus it's probably not safe to leave a tube amp on unattended (no one home) for any length of time. I turn mine on and let it warm up for a half hour before using and turn it off when I leave the house. Tube amps can catch fire- heck anything electrical can catch fire if left on and unattended. Mitch

I find a nice bluetacked computer fan on top of my LDII's power supply keeps it cool if not cold. Reducing fire risk as the amp normally reaches 120 c. No problem with heat on the tubes or microphonics.

The real issue with microphonics and these amps is not putting them anywhere near other power sources. Such as power leads, computers, mobiles, anything really that pushes out power. I say this because you have to tap the amp fairly hard to get any ringing in the tubes.

If you use the fan the tubes won't get hot and cold again when you turn it on and off and this should actually increase the life span of the tubes and other components as well as keeping the amp sounding at it's best.

The amps normal running temp as above does not increase sound quality. I think it decreases it as the components should not get that hot and their performance will be affected negatively. The LDII only "sounds" really warm when its been on for week. Slight exageration but you know what I mean.

 

[Hirsch]

Quote:

Originally Posted by robm321 I never left my tubes going 24/7, but I had an issue with hum in one channel. I brought it in for repair and now it is silent. The MG head (older versions) have had these issues with them.

The hum issue in the MG Head was due to wire placement. The audio signal wires were placed too close to the power transformer, so that they could pick up transformer hum unless they were placed exactly right. When I had one that had single channel hum, I simply moved a wire from one side of the transformer to the other. No more hum. Took all of five minutes to do.

NOTE: Tube amps can contain dangerous voltages, even when unplugged. Do NOT open a tube amp, even for something simple like I just described, unless you know how to do it safely.

 

[tourmaline]

Tubes should live at least couple of thousand hours. Some military tubes have 10.000 expectansy. Input tubes live longer then output tubes!Output tubes are used for the power, hence burn faster. But only 1 month is really fast, maybe faulty tube. 24/7 will burn tubes fast though. I never would do that!

 

[braillediver]

“I find a nice bluetacked computer fan on top of my LDII's power supply keeps it cool if not cold. Reducing fire risk as the amp normally reaches 120 c.”


120 deg C is boiling water not a Fire. The temperature of the tubes has nothing to do with the potential fire hazard. It’s the High Voltage in the Transformers, it’s the High Voltage Caps that might Explode and ooze and burn. It’s the power resistors that get warm and fail. It’s any number of things inside the amp that can and will burn.

To each their own but on something like a fire hazard I will not take idle banter from an internet posting as gospel. Consider 63 posts and 3 weeks on Head-Fi for what it’s worth- not much.

So basically your fan doesn’t do squat in an effort to reduce fire hazards and I hope to God you don’t live in my apartment complex.

I’m no expert But the vacuum tubes are meant to operate at certain temperatures. If you wanted to run the tubes cool to preserve life then there would be at least one commercial amp that actively cools the tube = not blowing air on them but actively refrigerates them like with a Peltier Cooler- I have never heard of an artificially cooled tube amp.


“The amps normal running temp as above does not increase sound quality. I think it decreases it as the components should not get that hot and their performance will be affected negatively.”

A “properly” designed amp will run at the temperature it was designed to run at. Some amps run hot and others don’t. You’re not overclocking a computer where running it cooler improves performance. Stuff gets hot with high voltages and as such when using high voltages stuff gets hot. You can’t determine whether an amp is good or bad by the temperature it runs at.


Mitch

 

[Labtek]

Quote:

Originally Posted by braillediver “I find a nice bluetacked computer fan on top of my LDII's power supply keeps it cool if not cold. Reducing fire risk as the amp normally reaches 120 c.” 120 deg C is boiling water not a Fire. The temperature of the tubes has nothing to do with the potential fire hazard. It’s the High Voltage in the Transformers, it’s the High Voltage Caps that might Explode and ooze and burn. It’s the power resistors that get warm and fail. It’s any number of things inside the amp that can and will burn. To each their own but on something like a fire hazard I will not take idle banter from an internet posting as gospel. Consider 63 posts and 3 weeks on Head-Fi for what it’s worth- not much. So basically your fan doesn’t do squat in an effort to reduce fire hazards and I hope to God you don’t live in my apartment complex. I’m no expert But the vacuum tubes are meant to operate at certain temperatures. If you wanted to run the tubes cool to preserve life then there would be at least one commercial amp that actively cools the tube = not blowing air on them but actively refrigerates them like with a Peltier Cooler- I have never heard of an artificially cooled tube amp. “The amps normal running temp as above does not increase sound quality. I think it decreases it as the components should not get that hot and their performance will be affected negatively.” A “properly” designed amp will run at the temperature it was designed to run at. Some amps run hot and others don’t. You’re not overclocking a computer where running it cooler improves performance. Stuff gets hot with high voltages and as such when using high voltages stuff gets hot. You can’t determine whether an amp is good or bad by the temperature it runs at. Mitch

Please don't take offence, and hold on a second, I never said it eliminated fire risk I just said it reduced it. Caps will blow if they get too hot or overloaded and the oil in them causes a fire. If they are cool the chance of them blowing is reduced as far as the heat eliment is concerned. I do live in an apartment complex but in London and the fire protection system has capacitors and high power resistors along with other components in it and its on 24/7. My Freezer gets hot at the back but I don't switch it off. I leave my washing machine and dryer on at night because its cheaper and the instructions don't mention a risk involved. transformers are integrated into a lot of plugs these days. I smoke and so does half of London and yes there are fires. The great fire was a good example. But I'm not going to do everything by the book or I'd never get out of bed, it's a busy city. My amp is less likely to catch fire if it isn't hot because the oil in caps needs to get to a certain temp before it turns to gas and can combust even with sparks or shorts or if the cap explodes which the breaker or fuse sorts out as with the transformers. The resistors etc, will not combust the amp unless they have something to ignite and PCB's are flame retardent. So I figure a fan is a good idea-only to reduce the fire risk, of burning the coils or blowing the caps to that of any other appliance left on at night. Fair I think.
Tube radio and transmitters have been used by the military and society 24/7 as a matter of necessity. But I did'nt say you should leave your amp on for 24/7 ad infinitem, thats lunacy (but the weekend might). I apologise If my "slight over exageration" comment indicated this but I've got to say it does sound better after over 24 hours.
High power amps have built in fans to keep mosfet's cool and stop them and other components failing due to the length of service (i.e five day festivals) so I figure whats the difference. Works for me and keeps the misses of my back when she's cleaning around it. I apologise if I come across as a bit over confident with my posts but I've been around sound a good few years now (maybe not computers) and not hurt a soul and fixed a good few probs. I hope I've fixed this one.
I certainly agree that digging about in an amp when it's on with no experience is no good idea.

 

[Uncle Erik]

Don't compare apples to oranges. Some products (e.g. freezers and milspec communications gear) are engineered to be on 24/7. A headphone amp built to economize on cost is not. That's like saying that since your car can drive on the road it can also tow a 20,000 pound trailer. Maybe your vehicle was engineered for that, maybe not. You have to look at the duty cycle of your gear and use it accordingly. Reading a manual only takes a minute anyway.

And besides, even if it is safe to leave on 24/7, do you really want it consuming power when you're not using it? You do get a bill from the power company, right?

 

[Jbucla2005]

Quote:

Originally Posted by Uncle Erik Don't compare apples to oranges. Some products (e.g. freezers and milspec communications gear) are engineered to be on 24/7. A headphone amp built to economize on cost is not. That's like saying that since your car can drive on the road it can also tow a 20,000 pound trailer. Maybe your vehicle was engineered for that, maybe not. You have to look at the duty cycle of your gear and use it accordingly. Reading a manual only takes a minute anyway. And besides, even if it is safe to leave on 24/7, do you really want it consuming power when you're not using it? You do get a bill from the power company, right?

I leave 2 of my tube amps on 24/7 right now and its because I use them daily and am afraid that switching them on and off too much will degrade the signal tubes. I have also heard the average lifespan of a tube is 40 years. I am not sure if what I am doing is the best thing but the signal tubes I use are rare and expensive and I have heard these smaller signal tubes are especially sensitive to on/off cycles. If someone can prove to me I'm wearing down the life faster I'll probably switch to turning them on and off once or twice a day, but I haven't really been able to discern a clear answer on this (as far as tubes go... as for other components, I have heard things like to be left on since the on/off cycle is stressful.)

 

[Labtek]

Quote:

Originally Posted by Uncle Erik Don't compare apples to oranges. Some products (e.g. freezers and milspec communications gear) are engineered to be on 24/7. A headphone amp built to economize on cost is not. That's like saying that since your car can drive on the road it can also tow a 20,000 pound trailer. Maybe your vehicle was engineered for that, maybe not. You have to look at the duty cycle of your gear and use it accordingly. Reading a manual only takes a minute anyway. And besides, even if it is safe to leave on 24/7, do you really want it consuming power when you're not using it? You do get a bill from the power company, right?

I'm going to go up the apples and pears (stairs) on this one and let sleeping dogs lie but Jbucla's right someone should check it out once and for all. Your minds need to be made up as to whether tube amps are a fire risk or not. If they are then you should only have them on when your in the room. If they are not a fire risk then you should do what you like. I don't see any argument. Please give a difinitive answer someone before this one really does some damage either to someones ego or their residence. REVIEW ON FIRE SAFETY OF TUBE AMPLIFIERS and give options. It is all very well to overload someones apple cart with opinion but we need facts that are backed up by recognised literature that proves the point and not politiking on the subject. This is obviously a tender area that has been avoided for political if not misinformed and unprecedented reasons I hope that we might resolve this issue in another thread.

 

[sacd lover]

Quote:

Originally Posted by Jbucla2005 I leave 2 of my tube amps on 24/7 right now and its because I use them daily and am afraid that switching them on and off too much will degrade the signal tubes. I have also heard the average lifespan of a tube is 40 years. I am not sure if what I am doing is the best thing but the signal tubes I use are rare and expensive and I have heard these smaller signal tubes are especially sensitive to on/off cycles. If someone can prove to me I'm wearing down the life faster I'll probably switch to turning them on and off once or twice a day, but I haven't really been able to discern a clear answer on this (as far as tubes go... as for other components, I have heard things like to be left on since the on/off cycle is stressful.)

Wherever you got your info .... thats incorrect. There is no tube I have ever heard of that lasts 40 years with continuous use. The longest lasting tubes live approximately 10,000 hours and most far less. Leaving your tubes on 24/7 is only wearing them out as fast as possible. At the rate your are going the tubes will be dead in a little over a year, assuming a 10,000 hour lifespan.

 

[creeky]

Quote:

Originally Posted by Labtek I find a nice bluetacked computer fan on top of my LDII's power supply keeps it cool if not cold. Reducing fire risk as the amp normally reaches 120 c. No problem with heat on the tubes or microphonics.

I would seriously recommend not leaving the LDII of all amps on 24/7 as you live in the UK. If you look at the transformer the primary winding is designed for 220 volt mains not the 240v mains we have in this country. I brought the LDII on a group buy over on another forum where most of the amps purchased failed. When my LDII died it had been left on for about 30mins when I noticed a faint whiff of acrid smoke. This was followed by blue smoke pouring from the amp itself.

As for the original poster, it may be worth checking the tube sockets before writing off the tubes. I recently had a hiss/hum/cutting out problem with one of my amps and it turned out to be a cooked contact. After soldering in a new socket the problem was solved

 

[tkam]

Quote:

Originally Posted by Jbucla2005 I leave 2 of my tube amps on 24/7 right now and its because I use them daily and am afraid that switching them on and off too much will degrade the signal tubes. I have also heard the average lifespan of a tube is 40 years. I am not sure if what I am doing is the best thing but the signal tubes I use are rare and expensive and I have heard these smaller signal tubes are especially sensitive to on/off cycles. If someone can prove to me I'm wearing down the life faster I'll probably switch to turning them on and off once or twice a day, but I haven't really been able to discern a clear answer on this (as far as tubes go... as for other components, I have heard things like to be left on since the on/off cycle is stressful.)

I really can't think of any case where leaving tubes running 24/7 would be a good thing. Sure the on/off cycles are "hard" on tubes but it won't degrade the life of the tube nearly as fast as leaving them on 24/7 will.

Here's a good cheap test you can do. Get two identical lamps and use identical light bulbs in each. Leave one on 24/7 and turn the other one on/off as necessary. The one you leave on 24/7 will die much sooner and the same principle applies to tubes.

Also as a few other people have mentioned it's really not a good idea to leave something producing as much heat as tubes do on unattended.

 

[Jahn]

Quote:

Originally Posted by sacd lover Wherever you got your info .... thats incorrect. There is no tube I have ever heard of that lasts 40 years with continuous use.

Well a Lightbulb is sorta like a tube...sorta!