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Does it matter if tube amp is tilted?

jjaaam

Member
Messages
919
Tilting a tube amp makes the electrons flow from the plate towards the bottom side edge of the tube glass, then bounce back up to the grid, as opposed to falling to the center of the bottom glass before bouncing. This is a result of gravity, and creates a subtle harmonic slightly less than 3.75 octaves above the 5th element. But only if powering the amp with 110v and with a non grounded plug while playing a 50's Telecaster. And if you turn the amp upside down, as Sid McGInnis does his 1963 Fender Showman, all of the electrons are forced, by gravity, to reside entirely on the plate, where they fry like microscopic eggs into a sonic frenzy before further splitting into a macroscopic mashup of atoms on the grid, resulting in a tonal blast of near nuclear proportions, commonly called mojo.
Really? Is that true (echoing Chris Farley)?
 
Messages
5,048
Some amps are designed to dissipate heat through vents on the back, so they’ll run a bit hotter if tilted. The amp isn’t going to explode from overheating from being tilted back a bit. But some people are pretty anxious about heat around their tubes, so it’s worth mentioning.

Theoretically, a tube is more prone to shorting and uneven heating if it’s on its side, but again a bit of tilting isn’t likely to make a difference in an otherwise properly functioning tube set. I have amps that mount the tubes horizontally and haven’t had issues with them, so I wouldn’t worry about it much.

In short, there’s some theoretical drawbacks, but in practice I’d say any real world disadvantages are negligible.

Gawd, these guys are funny!!
Are they though?
 

metropolis74

Member
Messages
824
If I tilt a tube amp so it's angled slightly upwards, could that have any negative repercussions for the functioning of the amp in any way, providing it's secure and does not fall? I assume not, but to be honest every little thing to do with music gear and electronics has so many caveats and random things that can go wrong or that 'it's best to avoid', that I thought I may as well ask.
Your amp will be fine.

For many years things like this had tubes in their communications systems and tilted quite often.
 

SgtThump

Silver Supporting Member
Messages
8,157
It won't hurt. If it did, Marshall would've have put a "tilt" control on the Marshall Origin amp that raises and lowers little legs on the front of the amp.
 

Steppin' Wolfe

Silver Supporting Member
Messages
5,781
Many tubes used in such situations have special requirements for withstanding G-forces, vibrations, and other such special demands.
 
Messages
5,048
I've never heard that before, do you have a source or explanation on that?
Just have a look at the heater or screen and their proximity to the cathode and plate. As they loosen up due to heat cycling they can short. They need not physically touch to cause problems.

With the tube horizontal, gravity aids in allowing for shorts. I’ve only had it happen once or twice, which is why I said “theoretical”. I’d consider it best practice to operate a tube upright if that’s the orientation of its design. But in most cases, tilting it sideways isn’t going to cause problems.
 

Bluefugue

Silver Supporting Member
Messages
371
If I tilt a tube amp so it's angled slightly upwards, could that have any negative repercussions for the functioning of the amp in any way, providing it's secure and does not fall? I assume not, but to be honest every little thing to do with music gear and electronics has so many caveats and random things that can go wrong or that 'it's best to avoid', that I thought I may as well ask.
I know exactly what you mean. I don’t think tilting the amp will affect it in any way, but there are often little dangers you don’t know about then when something happens, people are like, “oh, man, you should never do that,” lol.
 

fjblair

Gold Supporting Member
Messages
14,503
Tilting a tube amp makes the electrons flow from the plate towards the bottom side edge of the tube glass, then bounce back up to the grid, as opposed to falling to the center of the bottom glass before bouncing. This is a result of gravity, and creates a subtle harmonic slightly less than 3.75 octaves above the 5th element. But only if powering the amp with 110v and with a non grounded plug while playing a 50's Telecaster. And if you turn the amp upside down, as Sid McGInnis does his 1963 Fender Showman, all of the electrons are forced, by gravity, to reside entirely on the plate, where they fry like microscopic eggs into a sonic frenzy before further splitting into a macroscopic mashup of atoms on the grid, resulting in a tonal blast of near nuclear proportions, commonly called mojo.
Brilliant. Should be a sticky.
 

Jecht

Member
Messages
1,426
It also unbalances the torodial transformer resulting in an unstable warp field when cranked up to 11. Under 11, subspace field fluctuations are kept at a minimum as long as tilt angles do not exceed maximum recommended limits of 30° in any direction relative to inertial damper force.
 

HotBluePlates

Member
Messages
11,998
... Theoretically, a tube is more prone to shorting ... if it’s on its side ...
I've never heard that before, do you have a source or explanation on that?
Some tubes have suggested mounting arrangements for both vertical and horizontal mounting/operation.
...
Consider the power tube below:


The glass has been removed, and we see a black plate/anode surrounding the other bits inside the tube. Now let's remove that anode and see what's underneath:



In the middle is a cathode sleeve, coated with a whitish oxide coating (that releases electrons when it gets hot). Around that cathode are several helical-wound grids, which sit in the space between the cathode and anode/plate.

There are 3 pairs of support rods, an inner pair for the Control Grid (G1), a middle pair for the Screen Grid (G2), and an outer pair (really quad, as there are 2 rods on either side) for the Suppressor Grid (G3).

Let's rotate the tube to see these side-on:


You will see that over a 360º arc, there are exactly 2 points where any grid is supported. If those grid wires get hot enough, they might sag. You may notice the middle grid (screen, G2) is not very far away from the control grid. If the screen sags far enough, it could short-circuit to the control grid (which will cause the tube to lose bias and melt).

I only retained one of @Steppin' Wolfe's data sheets in the quote above. Page 5 of that sheet says if the KT88 is mounted horizontally, to keep Pin 4 and Pin 8 in a vertical plane.

If you held one of the old Genalex KT88's in your hand you would see aligning those two pins in a vertical plane orients the grid support rods like the middle photo above: the support rods are vertical, one over the other, and keep the grids from sagging downward.​
Gravity tries to pulls a hot, sagging grid downward, so there was a specific "best orientation" to fight that.​
For any other tube, the same could be done by looking at the individual tube. However a different brand might not put its support rods in the same place relative to tube-pins.​
 
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aeolian

Member
Messages
6,447
Fender amps had the tubes oriented with the grids perpendicular to the face of the amp so that if they were tilted back on the legs things didn't sag into each other. If the amp you're considering has the tubes in a similar orientation then there's no issues.
 

Geetarpicker

Member
Messages
3,039
I’ve blown 3 sets of Tung-Sol 6v6 tubes in the last couple years in an amp that coincidentally was tilted back every time I had a tube go short. Running 405v B+ and a bias of about 22ma seems like a conservative enough situation. Alas had to to move back to JJ 6V6s which never die. Hmmm, that said maybe there is something about tilting the amp back to consider?
 

Guppie

Member
Messages
1,451
If I tilt a tube amp so it's angled slightly upwards, could that have any negative repercussions for the functioning of the amp in any way, providing it's secure and does not fall? I assume not, but to be honest every little thing to do with music gear and electronics has so many caveats and random things that can go wrong or that 'it's best to avoid', that I thought I may as well ask.
Okay, I'm going against the trend and try to actually answer your question.
With the amp tilted back the heat is going to build up more around the chassis. This isn't really a problem unless you have an amp that is sensitive to overheating (some Marshall combos come to mind). If you think the heat is a problem that just put a little table fan behind the amp.
Otherwise, it's better for you, the sound engineer and the audience to have the amp pointing at you and not them.
 

HotBluePlates

Member
Messages
11,998
I’ve blown 3 sets of Tung-Sol 6v6 tubes in the last couple years ... every time I had a tube go short. ...
Except we can find similar tales from owners whose amps always sit upright. Sorry, but modern tubes are a quality crapshoot.

That said, I've only had one tube outright fail in decades of tube use, and it was an RCA 6L6GC that shorted plate-to-heater. That tube failed in an amp sitting upright.
 






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