Exposed Preamp Tube Protection in Small Chassis

[jbrrrrr]

Let's suppose you're building a small tube preamp or a mini-amp-head with triode-pentode tubes in a smaller Hammond-type enclosure.  The tubes are sticking up through holes in top of the chassis by about 1" or so - what are some preferred ways of protecting the exposed tubes that are simple, effective, and sharp-looking for DIY projects?

I sometimes see an approach kind of like this Effectrode preamp pedal:



I've been able to find a fair amount of inexpensive threaded drawer and cabinet pulls that will get in the ballpark of this idea without requiring any additional fabrication, but I don't totally love the way this looks and I have a nagging feeling that there's a chance of something wedging/poking between the "roll cage" and cracking a tube when being loaded into/from a car or something.   

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The other thing I often see is a kind of fabricated mesh cage, like the Vox Night Train, which I think I could get close to with some perforated aluminum from Home Depot if I had access to a metal brake:



(There's also a Hammond enclosure that has a matching tube cage available for it, but I think it only comes in one specific size, and last I checked, buying both units clocked over $100 which I'd rather spend on fancy capacitors)

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I'm wondering if there are any other clever ways to protect exposed preamp tubes in a small box format that would be worth considering.  I keep circling around some kind of an idea involving a lightweight mesh or wire rectangle that could be bracketed down on the sides above the tubes - maybe even a pencil holder or something - but that's the best I've got at the moment.

Anyone have any suggestions they wouldn't mind sharing?

[Merlin]

I keep circling around some kind of an idea involving a lightweight mesh or wire rectangle that could be bracketed down on the sides above the tubes

That reminds me of the Black Finger

I wish you could buy something like these easily!

Buying both units clocked over $100 which I'd rather spend on fancy capacitors

I'd say your priorities are all wrong! 

[tubeswell]

Chop the baubles off this, screw it to your chassis with little P-clamps, and call it the tube toaster.

[Rontone]

I have a Mesa Boogie Bottle Rocket pedal, that has a bent piece of sheet metal over the tubes that is simply screwed in either side with knurled thumbscrews

[jbrrrrr]

has a bent piece of sheet metal over the tubes that is simply screwed in either side with knurled thumbscrews

Oh awesome - this is just the sort of thing I was hoping to see some different examples of.

[acheld]

I have a Gurus Echo pedal with an embedded tube mounted horizontally. 

When I first got it, I thought the tube might overheat, but it has been years with daily use and it just keeps on echoing . . .

Like you, I worry about tubes sticking out of pedals.   They aren't called stomp boxes for nothing! 

[tubeswell]

if I had access to a metal brake:

Practical investment that every self-respecting tool guy should have (I’ve got a similar bench top mounted solid bar brake for chassis work).


https://www.kangindustrial.com.au/collections/brake/products/173134

[jbrrrrr]

if I had access to a metal brake:

100% agree - in an ideal world, I'd be bending my own chassis and being able to fab clever little solutions things like tube shield/covers with little to no issue with the tools I would have at home.  Space is at a premium for apartment dwellers in the great social experiment of California unfortunately, so it's tough to house bigger pieces of tooling.

I've been looking at the smaller and inexpensive 12" vice clamp brakes for bends in the middle area of longer pieces of metal, and maybe pairing it with a sheet metal folding tool (see link below) to just handle 3/8" folds on the edges of things for a lip to screw mount into (like some kind of tube guard made out of an aluminum strip - I imagine the smaller 12" brakes from like Harbor Freight probably wouldn't do great at creating a narrow lip on each end if I wanted to screw it down that way, but could easily handle the bends 1" or more past the edge of a sheet.)

Then again, I can't really think of a time that trying to be clever about inexpensive and space saving tool solutions that didn't involve me just buying the cumbersome thing in the end anyway so who knows.  Maybe something on AliExpress will inspire a new source of confidence.

Really, the larger solution is that I need a garage, since I'm clearly not seeing myself wanting to build *less* things as time moves on.

https://www.lowes.com/pd/Klein-Tools-Folding-Tool-18-Inch/5015642093

[tubeswell]

Apartment dwelling aye? Maybe see if Ikea or someplace like that has a pro-forma internal fold-away tool cupboard with foldaway bench that fits in your laundry, hallway or spare room that you can mount a vice and a folding brake onto (and plug your soldering iron into)? They really should think of these things for guys like us when they design apartments.

[jbrrrrr]

I have a Gurus Echo pedal with an embedded tube mounted horizontally. 

I've built a few of the DIY PCBs from Conspiracy to Commit electronics (https://c2celectronics.com/), and he's developed a pretty solid system of mounting 1 or 2 tubes inside a hammond pedal enclosure using right angle PCB satellite boards, and having vented "lines" drilled out by Tayda as part of their enclosure drilling service.  It works great for pedals, and he figured out a way to make the glowing filament of the tube more "visible" by putting an LED backlight underneath the tube, which shines through more through the vented cutouts.

It works well because the power supply is just a NE555 based SMPS design that powers the filaments from 12V and then converts 12VDC to 250-300VDC, and one or two 12ax7s is fine running like this.  For something that has an actual PT and perhaps an output or line transformer, I don't think mounting tubes on the interior would be the best use of space, and in spite of the problems with keeping them safe, mounting them to be visible outside the chassis is a neat look for bigger boxes.

[Merlin]

In my recent pedal design I didn't protect them at all, but if I took it on the road I guess I would make a folded sheet metal cowel, probably attached to the bottom plate.

[jbrrrrr]

but if I took it on the road I guess I would make a folded sheet metal cowel, probably attached to the bottom plate.

I like this idea though - I hadn't thought of hanging half the tube out of the side of the box.  As you mentioned, it still may have the issue of needing protection of some sort, but it's another interesting way to mount preamp tubes in a small chassis that isn't poking through the top or buried inside the enclosure.  This presentation looks really nice, Merlin!

[DummyLoad]

In your opening post pic, those brackets look like relay rack handles. Order from Mouser or DigiKey. Guessing at the size, handles are for a 2RU rack.

https://www.penn-elcom.com/us/1-5u-chrome-rack-panel-handles-r1265-105uc

--Pete

EDIT - Added a possible source.