crash cours on tube amps

[agedhorse]

Modern guitar amps operate at notably high plate voltages compared to those of ye olde days?

Yes, higher voltages than a typical pro audio or industrial type amplifier. This is in part to get as much power as possible out of the tube, even if the lifespan degrades. So a typical guitar amp might get 3 years or 2000 hours on a set of tubes by driving the snot out of them, the same tube operated conservatively might get 5000-10000 hours. The guitar amp market is different.

I have designed preamps using the more industrial performance curves, where I have also minimized noise (electronic as well as microphonic) and there are some of these devices that are well over 20 years old and still operating to spec on the original tubes (and caps... so much for needing to replace caps every few years like the internet old wives' tales might demand) without any problems. Think about it for a minute and it will become obvious why these crazy tube and cap failure-mongers are (generally) full of crap. The telephone companies used tube amplifiers for a variety of purposes, including the driving of long distance equalized lines and repeaters. These amplifiers (or banks of hundreds) would operate 24/7 for decades with minimal maintenance, but the circuits were also designed to prolong tube life. I have heard that they would typically shoot for a minimum design life of 20k hours and often get up to 50k+ hours. That's pretty incredible.

 

[Korladis]

Uh, define "modern." Many modern amps don't have plates to supply.

My post was obviously a response to and question directed at AgedHorse, in reference to what he said about newer guitar amps driving their tubes within an inch of their lives.

Yes, higher voltages than a typical pro audio or industrial type amplifier. This is in part to get as much power as possible out of the tube, even if the lifespan degrades. So a typical guitar amp might get 3 years or 2000 hours on a set of tubes by driving the snot out of them, the same tube operated conservatively might get 5000-10000 hours. The guitar amp market is different.

I have designed preamps using the more industrial performance curves, where I have also minimized noise (electronic as well as microphonic) and there are some of these devices that are well over 20 years old and still operating to spec on the original tubes (and caps... so much for needing to replace caps every few years like the internet old wives' tales might demand) without any problems. Think about it for a minute and it will become obvious why these crazy tube and cap failure-mongers are (generally) full of crap. The telephone companies used tube amplifiers for a variety of purposes, including the driving of long distance equalized lines and repeaters. These amplifiers (or banks of hundreds) would operate 24/7 for decades with minimal maintenance, but the circuits were also designed to prolong tube life. I have heard that they would typically shoot for a minimum design life of 20k hours and often get up to 50k+ hours. That's pretty incredible.

Oh I see. Trying to squeeze as much power out of as few tubes as possible?

Also I've read that biasing tubes on the "hot" side gets you more power, but wears them out faster, while biasing them on the "cold" side makes them last longer but with less power available. Is that true?

 

[Old Garage-Bander]

My post was obviously a response to and question directed at AgedHorse, in reference to what he said about newer guitar amps driving their tubes within an inch of their lives.


Oh I see. Trying to squeeze as much power out of as few tubes as possible?

Also I've read that biasing tubes on the "hot" side gets you more power, but wears them out faster, while biasing them on the "cold" side makes them last longer but with less power available. Is that true?

OK. Got it. Modern tube amps. Thanks.

 

[Korladis]

OK. Got it. Modern tube amps. Thanks.

I mean, this is a thread about tube amps, and post I was quoting was also about tube amps...

 

[Old Garage-Bander]

I mean, this is a thread about tube amps, and post I was quoting was also about tube amps...

Yes! I said I got it. Thanks again.

 

[JGbassman]

Always great information when you guys get rolling, and I even feel smarter after reading what @agedhorse has to say, lol.

I'm still trying to learn about tube amps, as they fascinate me. I love mine, and will never part with it. I need to do more deep reading regarding the magic of tubes.

Thanks to all that unselfishly give up their knowledge.

 

[agedhorse]

My post was obviously a response to and question directed at AgedHorse, in reference to what he said about newer guitar amps driving their tubes within an inch of their lives.


Oh I see. Trying to squeeze as much power out of as few tubes as possible?

Also I've read that biasing tubes on the "hot" side gets you more power, but wears them out faster, while biasing them on the "cold" side makes them last longer but with less power available. Is that true?

Yes, this is true.

There are better ways to reduce your the stress on tubes, goes to load lines and plate/screen/grid parameters and what you do with them.

 

[Korladis]

Yes, this is true.

There are better ways to reduce your the stress on tubes, goes to load lines and plate/screen/grid parameters and what you do with them.

I mean, I haven't had to replace tubes often in my D-180, despite driving it hard and using it on the road. I play in two doom bands, so I personally think the use rate of tubes that people talk about sometimes with tube amps is a bit overstated.

 

[Old Garage-Bander]

I mean, I haven't had to replace tubes often in my D-180, despite driving it hard and using it on the road. I play in two doom bands, so I personally think the use rate of tubes that people talk about sometimes with tube amps is a bit overstated.

I know it's probably counter to a doom bassist... but gosh, sure sounds like you take good care of your gear.

 

[Korladis]

I know it's probably counter to a doom bassist... but gosh, sure sounds like you take good care of your gear.

What's that supposed to mean?

 

[Old Garage-Bander]

What's that supposed to mean?

Well aren't doom bands like the bad boys of metal?
I mean shouldn't you've already tossed your amp off the stage a few times by now?

 

[Korladis]

Well aren't doom bands like the bad boys of metal?
I mean shouldn't you've already tossed your amp off the stage a few times by now?

Not really, no.

Despite the ridiculous volumes, it's a bit more "chill" of a crowd than in some parts of the scene. Perhaps due to our enthusiasm for a certain herb.

 

[Old Garage-Bander]

Not really, no.

Despite the ridiculous volumes, it's a bit more "chill" of a crowd than in some parts of the scene. Perhaps due to our enthusiasm for a certain herb.

Well I must take fresh look at your genre then.

 

[okcrum]

Yes, higher voltages than a typical pro audio or industrial type amplifier. This is in part to get as much power as possible out of the tube, even if the lifespan degrades. So a typical guitar amp might get 3 years or 2000 hours on a set of tubes by driving the snot out of them, the same tube operated conservatively might get 5000-10000 hours. The guitar amp market is different.

I have designed preamps using the more industrial performance curves, where I have also minimized noise (electronic as well as microphonic) and there are some of these devices that are well over 20 years old and still operating to spec on the original tubes (and caps... so much for needing to replace caps every few years like the internet old wives' tales might demand) without any problems. Think about it for a minute and it will become obvious why these crazy tube and cap failure-mongers are (generally) full of crap. The telephone companies used tube amplifiers for a variety of purposes, including the driving of long distance equalized lines and repeaters. These amplifiers (or banks of hundreds) would operate 24/7 for decades with minimal maintenance, but the circuits were also designed to prolong tube life. I have heard that they would typically shoot for a minimum design life of 20k hours and often get up to 50k+ hours. That's pretty incredible.

That sort of design found its way into the early electronic computers, in slightly different form. I got a first hand lesson in design for reliability in college when I got roped into restoring an IBM 650 as a favor to the EE dept. chair.

Thousands of 5963 (12AU7) and 5726 (6AL5). Many, many blinking lights. A small library of manuals, half of whose pages read "This page intentionally left blank". More 1% parts than I had ever seen before. A giant regulated power supply using selenium rectifiers. Straight out of 1950s sci-fi films.

Thankfully, my instructions ended something like "...and there are two dead machines in the basement you can use for parts."

 

[bassrich]

Never run a tube amp without a load (speaker), I think those Fenders want a 4 ohm load, you will get less power if you use an 8 ohm speaker for ex. Tube amps are the opposite of SS amps, it is better to run them at too low an impedance than too high. Always turn them on with the standby switch in the off position and wait at least 30 seconds to turn the standby to the on position, you'll wear out your power tubes too soon if you don't do that. I'm sure there are other things but those are important. They are not as delicate as people will have you believe and tubes last a lot longer than people who haven't owned them will say, there is nothing to be afraid of with a tube amp, just make sure you have the proper load on them when they're on.

by this do you mean turn on the amp with the standby switch in the play position?

 

[bobyoung53]

by this do you mean turn on the amp with the standby switch in the play position?

I always keep it off for 30 seconds then switch it to play, I turn the power to on, then wait at least 30 seconds and then turn the standby to on (play) gives the tubes a few seconds to warm up and keeps the high voltage off the plates and power tubes don't like plate voltage when the filaments aren't warmed up, this is me, I guess some people don't agree but when I haven't done this my tubes seems to wear out faster.

 

[bassrich]

I always keep it off for 30 seconds then switch it to play, I turn the power to on, then wait at least 30 seconds and then turn the standby to on (play) gives the tubes a few seconds to warm up and keeps the high voltage off the plates and power tubes don't like plate voltage when the filaments aren't warmed up, this is me, I guess some people don't agree but when I haven't done this my tubes seems to wear out faster.

Makes sense I was told to when turning it off to switch the stand by on (not play) and then wait a min then turn the power off