man, ya can sure go through output tubes in a hurry
- Thread starter PVFan
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Re: man, ya can sure go through output tubes in a hurry
I just googled cathode based amp cause I didn't know what you meant, and I found this.
"FWIW, and to further confuse the issue and stir up debate, I have another take on the subject:
Running tubes in true class A doesn't shorten their lifespan at all - they are rated by the manufacturer to run at a particular max plate dissipation, and as long as you don't exceed that rating, the tubes last their "normal" lifespan. Running them cooler will likely extend them beyond their normal lifespan, whatever that may be. Now, this doesn't change a damned thing, but it sure makes you feel better about running tubes at their max ratings when you look at it this way.
Actually, it is a common misconception that tubes in class A are running at their maximum all the time - they do indeed conduct *current* throughout the entire cycle, but the plate dissipation is not at maximum for the entire cycle. In fact, the average plate dissipation drops as the tube amplifies a signal. Dissipation is at maximum at idle, and drops to a minimum of half the idle power dissipation when putting out full power - the part of the total input power that is passed on to the load is subtracted from the idle dissipation in the tube, so they actually run cooler at full power than they do at idle. For more on the subject, read this paper: http://www.aikenamps.com/Why70percent.html
So, if you want to extend your tube life in a class A amp, play it at full volume all the time. When your bandmates tell you to turn down, inform them that you must play that loud to preserve the life of your valuable NOS output tubes.
Randall Aiken"
I just googled cathode based amp cause I didn't know what you meant, and I found this.
"FWIW, and to further confuse the issue and stir up debate, I have another take on the subject:
Running tubes in true class A doesn't shorten their lifespan at all - they are rated by the manufacturer to run at a particular max plate dissipation, and as long as you don't exceed that rating, the tubes last their "normal" lifespan. Running them cooler will likely extend them beyond their normal lifespan, whatever that may be. Now, this doesn't change a damned thing, but it sure makes you feel better about running tubes at their max ratings when you look at it this way.
Actually, it is a common misconception that tubes in class A are running at their maximum all the time - they do indeed conduct *current* throughout the entire cycle, but the plate dissipation is not at maximum for the entire cycle. In fact, the average plate dissipation drops as the tube amplifies a signal. Dissipation is at maximum at idle, and drops to a minimum of half the idle power dissipation when putting out full power - the part of the total input power that is passed on to the load is subtracted from the idle dissipation in the tube, so they actually run cooler at full power than they do at idle. For more on the subject, read this paper: http://www.aikenamps.com/Why70percent.html
So, if you want to extend your tube life in a class A amp, play it at full volume all the time. When your bandmates tell you to turn down, inform them that you must play that loud to preserve the life of your valuable NOS output tubes.
Randall Aiken"
Re: man, ya can sure go through output tubes in a hurry
RCA gray plate 6V6s and Sylvania 7591As - and original RCA 6EU7s and Telefunken ECC83s too.
I'm diming these amps and use them a few hours per week.
I've had EH, GTs, Tung-Sol, and Sovteks in other amps and they crap out on me or just plain sound awful. So far the only decent modern output tube I've liked is the JJs 6V6 or the Mesa STR-417s. The Mesas have lasted me over 15 years.
RCA gray plate 6V6s and Sylvania 7591As - and original RCA 6EU7s and Telefunken ECC83s too.
I'm diming these amps and use them a few hours per week.
I've had EH, GTs, Tung-Sol, and Sovteks in other amps and they crap out on me or just plain sound awful. So far the only decent modern output tube I've liked is the JJs 6V6 or the Mesa STR-417s. The Mesas have lasted me over 15 years.
Re: man, ya can sure go through output tubes in a hurry
I would agree - he might look into using 7189s instead as they're a bit more rugged.
I would agree - he might look into using 7189s instead as they're a bit more rugged.
SlyFoxx
Glossless
Re: man, ya can sure go through output tubes in a hurry
When I was gigging and rehearsing with my mesa LSS it was chewing through 4 EL84's every six months or so. An old Marshall (I think a dsl) I have was the same way.
When I was gigging and rehearsing with my mesa LSS it was chewing through 4 EL84's every six months or so. An old Marshall (I think a dsl) I have was the same way.
Mr 9finger
Digitally Challenged
Re: man, ya can sure go through output tubes in a hurry
I was talking to Trace from Voodoo amps not that long ago about getting my DSL modded. I don't much about tube amp mechanics yet, so I was just taking his word for it, but he mentioned that some of the stock transformers in the DSL/TSL amps were pretty crappy in the later production models and it was causing a lot of folks problems with tube life among other things.
Since Rob(RobSoundtrack), the bro I bought mine off of already had MM trannies put in, Trace said to not even bother with having any more mods done unless there was something very specific I wanted done to it.
I was talking to Trace from Voodoo amps not that long ago about getting my DSL modded. I don't much about tube amp mechanics yet, so I was just taking his word for it, but he mentioned that some of the stock transformers in the DSL/TSL amps were pretty crappy in the later production models and it was causing a lot of folks problems with tube life among other things.
Since Rob(RobSoundtrack), the bro I bought mine off of already had MM trannies put in, Trace said to not even bother with having any more mods done unless there was something very specific I wanted done to it.
Lazarus1140
New member
PVFan
Fudgeitallologist
Re: man, ya can sure go through output tubes in a hurry
yep. It's my Ghia head. Erksin's posts above were intriguing until I saw him list every tube type except EL-84s. Do you think my going through so many tubes is due more to the nature of EL-84s than it is due to the cathode-bias design? I've read that.
yep. It's my Ghia head. Erksin's posts above were intriguing until I saw him list every tube type except EL-84s. Do you think my going through so many tubes is due more to the nature of EL-84s than it is due to the cathode-bias design? I've read that.
Re: man, ya can sure go through output tubes in a hurry
I think it is VERY dependent on the quality of the tubes you're using, and maybe switching to 7189s might prolong the time between changes. I don't know how hard the CG is on tubes.
I think it is VERY dependent on the quality of the tubes you're using, and maybe switching to 7189s might prolong the time between changes. I don't know how hard the CG is on tubes.
Snoogles
Cranky-dologist
Re: man, ya can sure go through output tubes in a hurry
how do you know if you need new power tubes? are there tell-tale signs? what if you're only playing a 50-watter at living room levels in the first place?
do power tubes run down at the same rate regardless of the volume you run your amp? living room vs stage
if you're playing a 50-watt amp at living room levels, are new power tubes going to make a difference?
does brand make a difference?
how do you know if you need new power tubes? are there tell-tale signs? what if you're only playing a 50-watter at living room levels in the first place?
do power tubes run down at the same rate regardless of the volume you run your amp? living room vs stage
if you're playing a 50-watt amp at living room levels, are new power tubes going to make a difference?
does brand make a difference?
Re: man, ya can sure go through output tubes in a hurry
Brand most definitely makes a difference, not only in longevity but in actual sound.
The most common tell-tale sign is a drop in output volume. If you notice that you're lacking bass all of a sudden that can also be a tell.
If you aren't running the amp hard the tubes will definitely last longer than if you're cranking it night after night.
Brand most definitely makes a difference, not only in longevity but in actual sound.
The most common tell-tale sign is a drop in output volume. If you notice that you're lacking bass all of a sudden that can also be a tell.
If you aren't running the amp hard the tubes will definitely last longer than if you're cranking it night after night.
PVFan
Fudgeitallologist
Re: man, ya can sure go through output tubes in a hurry
I certainly will look into this, thanks! Options are nice to have
I certainly will look into this, thanks! Options are nice to have
glassman
Electron Herder
Re: man, ya can sure go through output tubes in a hurry
Yes and no.
Bias only sets the minimum current a tube passes...the power transformer sets the maximum. In a cathode bias amp, the cathode resistor does limit the maximum dissipation to some degree but the capability of the power supply has the greater effect. screen current control is also a factor. Two 18 watt amps may pass a clean 18 watts at maximum undistorted output, but, depending on power transformer design, the maximum distorted output of one may be 20 watts while the other may put out 36 watts. Published transformer specs are interesting but tell you absolutely nothing about behavior at different power consumption levels...only the designer knows that. It sounds like your amp has a power supply with a lot of capability which will over-dissipate the tubes to some degree causing them to wear quicker than some other amps.
If you like the tone of the amp then you may just have to chalk the accelerated tube wear up as a cost of doing business.
Yes and no.
Bias only sets the minimum current a tube passes...the power transformer sets the maximum. In a cathode bias amp, the cathode resistor does limit the maximum dissipation to some degree but the capability of the power supply has the greater effect. screen current control is also a factor. Two 18 watt amps may pass a clean 18 watts at maximum undistorted output, but, depending on power transformer design, the maximum distorted output of one may be 20 watts while the other may put out 36 watts. Published transformer specs are interesting but tell you absolutely nothing about behavior at different power consumption levels...only the designer knows that. It sounds like your amp has a power supply with a lot of capability which will over-dissipate the tubes to some degree causing them to wear quicker than some other amps.
If you like the tone of the amp then you may just have to chalk the accelerated tube wear up as a cost of doing business.
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