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[EOengineer]

Yeah, cuz when it comes time to re-tube them big-iron amps, it costs an arm and a leg. View attachment 53427

I more than likely have to retube my 2:90 this winter. I keep punting and know I’m playing with fire. 8 6L6s in that friggin thing.

OUCH.

Sorry for your loss.

 

[TSJMajesty]

I more than likely have to retube my 2:90 this winter. I keep punting and know I’m playing with fire. 8 6L6s in that friggin thing.

OUCH.

Sorry for your loss.

And 3 12ax7's.

 

[newholland]

The Mark amps can be super mid forward, that is why so many people use the eq in the V mode to pull some or most mids out.

The JP2C is a bit more mid forward but that Mark EQ can change that. I know some of the folks in here have Mark's w/o the EQ and a few of them put an EQ in the loop to make up for it. I "think" I have gathered from other users coments that the non EQ ones have differnt tone stacks that sort of make up for no EQ? I have not touched one though, just from what others have said about them still being absolutly brutal sounding amps and I know w/o the EQ my Mark V and JP2C sound very thin and shit.

im not sure if its different- but my iib has no eq and i usually dial the mids north of 5-6. it doesnt clean up super well without it, and it makes for way better low mids and bass- but i also run my presence almost flat out. :

 

[TubeStack]

And 3 12ax7's.

That's actually not many for a Mesa? My Electra Dyne has 7, and it's a low gain classic rock amp.

 

[gearJunkie]

That's actually not many for a Mesa? My Electra Dyne has 7, and it's a low gain classic rock amp.

when paired with a Triaxis, that's a total of 8 x 12ax7's and 8 x 6l6's.

 

[TSJMajesty]

That's actually not many for a Mesa? My Electra Dyne has 7, and it's a low gain classic rock amp.

Yeah but it's just a power amp. I was surprised when I first learned it had any.

 

[EOengineer]

Yeah but it's just a power amp. I was surprised when I first learned it had any.

Phase inverters.

 

[TSJMajesty]

Phase inverters.

If that's all they're doing, how fresh do they need to be? I also have a 2:90 probably due for a new set of tubes.

 

[TubeStack]

Yeah but it's just a power amp. I was surprised when I first learned it had any.

Ah, okay. Yeah, I see what you’re saying.

 

[EOengineer]

If that's all they're doing, how fresh do they need to be? I also have a 2:90 probably due for a new set of tubes.

My experience has been that I rarely if ever need to replace 12ax7s.

 

[TubeStack]

My experience has been that I rarely if ever need to replace 12ax7s.

Yeah, I have a stash of 12ax7 in case any ever go on me, but if I buy a used amp, I don’t worry about re-tubing those, just the power tubes.

And I only ever replace power tubes on my long-owned amps, when they wear out. Preamp tubes will last forever if they don’t have a catastrophic failure, is my understanding.

 

[TSJMajesty]

My experience has been that I rarely if ever need to replace 12ax7s.

Yeah, I have a stash of 12ax7 in case any ever go on me, but if I buy a used amp, I don’t worry about re-tubing those, just the power tubes.

And I only ever replace power tubes on my long-owned amps, when they wear out. Preamp tubes will last forever if they don’t have a catastrophic failure, is my understanding.

So since power tubes gradually wear out (not talking about a failure here, rather lifespan), how does one know they need replacing? Other than maybe swapping tubes from a known good amp.

Like in my case, with my Tri Axis/2:90, it's an early version, bought used, so I don't really have a reference to its sound when it was new. When I fire it up (rarely) it sounds good, but I'm not sure if it's at its best.

Also, do power amp tubes wear out just due to age, as in, if the amp isn't used very often?

 

[gearJunkie]

how does one know they need replacing?

In my experience with the 2:90, when the power tubes are approaching their end of life, I would typically notice occasional unexpected crackling sounds, even with no input and volumes set to zero. This would soon be followed by intermittent volume drops leading to significant loss of headroom and overall volume.

When I was performing and practicing with my band 5 nights a week, I would typically get around to replacing the power tubes every 2 years.

Now that I'm primarily a home player, my current set of power tubes are still going strong with around 6 years of (significantly less) playing time.

 

[laxu]

Also, do power amp tubes wear out just due to age, as in, if the amp isn't used very often?

No. Otherwise we would not have NOS tubes. When I got my Mark V, I slapped SED =C= tubes in it that are like a decade old. Work totally fine.

Steven Fryette says the things to avoid are vibration (e.g rolling the amp on a cart over cobblestones) and moving the amp when it's still hot. It can take something like 15-20 minutes for those tubes to fully cool down after turning off power, so if at all possible I'd just avoid moving the amp at that point, go help the drummer tear down and pack everything else.

Totally agree with @gearJunkie 's description of what it sounds like when the tubes are going. Don't mistake the phase inverter failing for bad power tubes though, as that will tend to manifest as the amp just cutting out.

Sometimes the tubes are not an issue either, as it could be e.g loose/dirty sockets or components around the tubes failing.

 

[TSJMajesty]

No. Otherwise we would not have NOS tubes.

Oh yeah, good point. I didn't think about that.

 

[TSJMajesty]

or components around the tubes failing.

What's typically first to go? The big capacitors?

 

[laxu]

What's typically first to go? The big capacitors?

Yeah those tend to go at some point, and likely should be checked after 10-20 years depending on how heavily the amp is used.

But sometimes some grid resistor fails etc. The most common culprit is still tubes followed by caps.