The right way up for Tubes in an amp chassis..

[Gold star]

From the earliest days, vacuum tubes in many guitar amps have been placed upside down in the chassis,( Fender being a classic example) with a few exceptions one being Marshall. I dont know if this design or feature was unavoidable but one thing is clear..heat rises and that heat degrades, or can degrade, other components in the amp. Agreed ? An example is where you see maybe 7 bottles at the back inc rectifier tube, in a 50 or 100 watt amp, that is a lot of heat. The other thing I see in smaller combos is the power tubes placed too close to the back of the speaker ..unacceptable, and this coming from famous brand names.

These things have been mentioned elsewhere, I don't know why amp makers don't use tube coolers/ dampers on tubes in their amps more often

 

[JMP/HBE]

Re: The right way up for Tubes in an amp chassis..

From the earliest days, vacuum tubes in many guitar amps have been placed upside down in the chassis, with a few exceptions one being Marshall. I dont know if this design or feature was unavoidable but one thing is clear..heat rises and that heat degrades, or can degrade, other components in the amp. Agreed ? An example is where you see maybe 7 bottles at the back inc rectifier tube, in a 50 or 100 watt amp, that is a lot of heat. The other thing I see in smaller combos is the power tubes placed too close to the back of the speaker ..unacceptable, and this coming from famous brand names.

These things have been mentioned elsewhere, I don't know why amp makers don't use tube coolers/ dampers on tubes in their amps...

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Most MESA combos have fans inside & Rectifiers are open in the back/front/top.
I have both & never had an issue.
In da 80's i put a fan on a 50 watt JMP head as only the 100 watt had a vent on top.
I have a 100 watt modified JMP and never had a problem.
Outdoor shows in direct sunlight in extreme heat {100+ degrees} could be a problem but other than that its not really an issue.
And you never really want a fan blowing directly on a tube.
Vacuum tube "boil" electrons and the normal operation is not a problem.
I do use tube rings [dampers].

 

[Empty Pockets]

Re: The right way up for Tubes in an amp chassis..

Sounds like you're worrying about a non-issue.

 

[NegativeEase]

Re: The right way up for Tubes in an amp chassis..

Well, Amps are designed to operate within certain temperature ranges -and that is part of the design

I have amps that are 40-60 years old in both configs without issue.

If anything Guitar amps are some of the most spacious and ventilated of most historical tube amplifier applications -except maybe UHF/VHF transmitters.

I don't believe this is something to worry about if you are keeping your amps properly maintained.

 

[dave74]

Re: The right way up for Tubes in an amp chassis..

My multi-watt triple has a nice fan built-in. It's my only amp with a fan though.
I read mesa was required/forced to do it by the safety people/gov.

 

[NegativeEase]

Re: The right way up for Tubes in an amp chassis..

My multi-watt triple has a nice fan built-in. It's my only amp with a fan though.
I read mesa was required/forced to do it by the safety people/gov.

I really don't prefer amps with fans -if I can avoid them -but with some amps it's just a must -especially high powered amps like with multiple 6550 pairs, If anything that oscillation from the fan is going to wear solder and pushfit connections before heat is going to wear components inside a head.

 

[Boogie Bill]

Re: The right way up for Tubes in an amp chassis..

I don't think that's true Dave, otherwise other amps would have them too. With Mesa it's a design choice.

And everybody knows that Marshalls don't start sounding good until that third set when they're hot and rockin'!

Bill

 

[PFDarkside]

Re: The right way up for Tubes in an amp chassis..

The guy that plays (or used to play) on SNL has a Fender head that he has upside down for heat dissipation. It think it’s on and running under stage lights for hours and hours at a time.

For combos it’s nearly inevitable isn’t it? My Mesa Road King has 6 power tubes, 2 rectifiers and who knows how many preamp tubes.... it’s “upside down” but has a fan. I’m sure the head version also has a fan too....

 

[chadd]

Re: The right way up for Tubes in an amp chassis..

The guy that plays (or used to play) on SNL has a Fender head that he has upside down for heat dissipation. It think it’s on and running under stage lights for hours and hours at a time.

For combos it’s nearly inevitable isn’t it? My Mesa Road King has 6 power tubes, 2 rectifiers and who knows how many preamp tubes.... it’s “upside down” but has a fan. I’m sure the head version also has a fan too....

Indeed, it does.

 

[Mincer]

Re: The right way up for Tubes in an amp chassis..

My Mesa Blue Angel has a fan, too. But I am sure while it was designed to last a long time, these things all have lifespans.

 

[dave74]

Re: The right way up for Tubes in an amp chassis..

I don't think that's true Dave, otherwise other amps would have them too. With Mesa it's a design choice.

And everybody knows that Marshalls don't start sounding good until that third set when they're hot and rockin'!

Bill

Do the other triple-rectifier versions have fans? (2-channel and original 3-channel)
Here is the thread where I read that it was a newly added requirement.
http://www.grailtone.com/forum/viewtopic.php?t=71355
4th post down

edit; that post is from the Mesa rep on the forum

 

[Gold star]

Re: The right way up for Tubes in an amp chassis..

Well, Amps are designed to operate within certain temperature ranges -and that is part of the design

I have amps that are 40-60 years old in both configs without issue.

If anything Guitar amps are some of the most spacious and ventilated of most historical tube amplifier applications -except maybe UHF/VHF transmitters.

I don't believe this is something to worry about if you are keeping your amps properly maintained.

what does maintained mean ? I've seen closed back valve combos ..that cant be a good thing and the guys at Marshall made a point regarding the recent Origin & Studio Marshalls of keeping the heat from the valves away from the other components...

 

[Gold star]

Re: The right way up for Tubes in an amp chassis..

Vox amps from the 60s had a reputation for running hot..hot enough to catch fire in some cases ! you cant call that a non issue...With SS of course, its very rarely an issue

 

[Gold star]

Re: The right way up for Tubes in an amp chassis..

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Most MESA combos have fans inside & Rectifiers are open in the back/front/top.
I have both & never had an issue.
In da 80's i put a fan on a 50 watt JMP head as only the 100 watt had a vent on top.
I have a 100 watt modified JMP and never had a problem.
Outdoor shows in direct sunlight in extreme heat {100+ degrees} could be a problem but other than that its not really an issue.
And you never really want a fan blowing directly on a tube.
Vacuum tube "boil" electrons and the normal operation is not a problem.
I do use tube rings [dampers].

I can see 8 tubes there.. what model is that ??

 

[Simon_F]

Re: The right way up for Tubes in an amp chassis..

Marshall made a big mistake with the JTM600 and JCM600 combos in the 90s - mounted the tubes sideways beneath the circuit board!

Those were great sounding, well-featured amps but they are mostly remembered for their reliability issues.

 

[NegativeEase]

Re: The right way up for Tubes in an amp chassis..

what does maintained mean ? I've seen closed back valve combos ..that cant be a good thing .

Proper bias set point checked, tube sockets cleaned, and good working tubes so the amp doesn't draw more current and run hotter than designed.

I mean, sure there are manufacturers and models out there where heat is a problem because the design is poor -but do the homework -the bad ones are known -There are models and derivative designs out there without issue for 70 years

Also, most tube electronics were enclosed with some basic vent ports back pre 1960s -it wasn't an unnatural thing, guitar amps aren't unusual -people have just used them generally longer than most diagnostic and transmission tube equipment.

 

[Jacew]

Re: The right way up for Tubes in an amp chassis..

Proper bias set point checked, tube sockets cleaned, and good working tubes so the amp doesn't draw more current and run hotter than designed.

I mean, sure there are manufacturers and models out there where heat is a problem because the design is poor -but do the homework -the bad ones are known -There are models and derivative designs out there without issue for 70 years

Also, most tube electronics were enclosed with some basic vent ports back pre 1960s -it wasn't an unnatural thing, guitar amps aren't unusual -people have just used them generally longer than most diagnostic and transmission tube equipment.

Isn't that a bit contradictory? Saying first it's not a problem, then acknowledging there is a problem with many amps with that design?

 

[NegativeEase]

Re: The right way up for Tubes in an amp chassis..

Isn't that a bit contradictory? Saying first it's not a problem, then acknowledging there is a problem with many amps with that design?

No, i didn't use the word "many" -thats more you twisting it, and in every single industry there are a portion of poorer designed or made products -that's just the bell curve and common sense.

Just buy quality, do your homework and maintain it correctly and you are fine -this is not an issue to worry about

 

[Jacew]

Re: The right way up for Tubes in an amp chassis..

No, i didn't use the word "many" -thats more you twisting it, and in every single industry there are a portion of poorer designed or made products -that's just the bell curve and common sense.

Just buy quality, do your homework and maintain it correctly and you are fine -this is not an issue to worry about

I was thinking it from engineering viewpoint. Yea it can be made to work with design, but simpler it is and less clever design it requires, more robust it will likely to be. Especially if made cheap.

Flipping chassis so tubes don't direct heat to other components seems simple enough, that it seems poorer design to begin with. But there may he reasons to do that, and well engineered shouldn't cause any trouble so it's not a bad thing automatically.

 

[NegativeEase]

Re: The right way up for Tubes in an amp chassis..

I was thinking it from engineering viewpoint. Yea it can be made to work with design, but simpler it is and less clever design it requires, more robust it will likely to be. Especially if made cheap.

Flipping chassis so tubes don't direct heat to other components seems simple enough, that it seems poorer design to begin with. But there may he reasons to do that, and well engineered shouldn't cause any trouble so it's not a bad thing automatically.

Well, Marshall was one of if not the first high gain amp -so maybe it makes sense that they were learned this made their amps dissipate heat better plus they wanted the weight in the bottom because they were designing stacks in a tall narrow head early on.

But I firmly believe that the oscillation from a fan that is hard coupled to the chassis will cause issues with solder joints before heat on the components will on a well designed amp -I have upside down Fenders that have the original components from 60 years ago.

I don't think 100plus watt 6550 amps have a choice thought -gotta have a fan.

Fender's original inverted arrangement comes from the desire for the controls to be on the top or angled and making more room from the speaker or enabling a smaller overall cabinet - I don't think heat was a concern in their original designs.

I've never had a heat problem though -except solid state amps ironically, but I buy quality proven amps, keep my valve amps dialed and keep the amps ventilated (not against the wall).