#1
I have a 2x12 combo tube amp with some garbage speakers in it. I also have a spare 4x12 cab with some nice vintage 30s in it. The 2x12 combo takes up a stupid amount of space if I sit it right on top of the 4x12, not to mention its practically about to tip over. I dont have an extra headshell to put the tube amp chassis in.

Is it a bad or stupid idea to take the tube amp chassis out of the combo headshell and just sit that right on top of my 4x12 (tubes and transformers facing up, innards of the chassis facing down). Obviously, if the chassis fell off it could get damaged, but are there any other dangers doing this, aside from touching a hot tube?

Thanks
#2
bad idea .... there is hugely dangerous voltage so if you touch something there is a real danger of killing yourself.

what I would do is take the chassis out and cut the combo down to the size of a headshell and then rehouse the chassis in that
#3
The amp will be fine, just don't poke around inside (which you already know anyway).

But you have nothing to worry about.
you should make a head shell just to protect it.
Last edited by Robbgnarly at Nov 14, 2014,
#4
It's fine. I run chasses like that all the time, it's not ideal (going to get dusty) but it's not like anything is going to jump out and bite you. Every tech in the world runs amps with the chassis open when diagnosing issues

"If you touch something" is like saying "if you shove your hand into a bandsaw." The solution is to not touch the dangerous part. It's not that hard if you're careful and understand the danger. Being irrationally afraid of something because you don't understand it is letting your fear subvert reality.

Just make sure nothing metal is under the chassis, and check to make sure it's not melting the tolex of the cab it's on. Might want to put it on a bit of wood or something to lift it off the cab, sometimes sharp edges on the inside of the chassis can cut the tolex.
#5
Yea Im not well versed on electrical components, but I am aware that the inside of the tube amp is quite dangerous to haphazardly stick my hand into. I was going to face the innards downwards so they were concealed between the chassis and the 4x12. Ideally, i would get a custom head shell but i cant afford it right now. Thanks for all of the replies guys
#7
Quote by Robbgnarly
Make your own headshell, it is a rectangular box for god sakes man


I live in an apartment and dont have a proper tool set/workspace. Building a box is easy, but its not as simple as just slapping a few boards together. Everything has to be sanded several times over which makes a mess, plus the construction process is noisy. And then, Im not very good at tolexing. I would probably try that roll on Duratex though if I ever construct one.
#8
How much risk would it pose to others, rememberig that amps retain dangerously high voltages after they have been switched off?
#9
Do you have a Lowes or Home Depot they will cut plywood or any wood you want into specific lengths. grab a bit of sand paper and some good wood glue and a clamp or 2. Or borrow some clamps from a friend.
#11
Yeah. Why not just move a couple of the speakers from the 4x12 into the combo cabinet until you can get a better solution together?
#12
Quote by Tony Done
How much risk would it pose to others, rememberig that amps retain dangerously high voltages after they have been switched off?

Practically none, considering you'd have to lift up the amp, turn it over, and stick your hand into the chassis. You're not going to kill yourself just casually brushing up against it or using the amp as it sits.

Obviously I wouldn't do this if you had kids in the house, or a big dog that might knock it over. Beyond that, though, I don't see any danger unless you have friends or family who are in the habit of manhandling your gear without asking first.

I would liken the danger of this to having a hot pot on the stove. Any sensible person is going to know better than to touch it to see if it's hot, and anyone who isn't sensible enough to do that is someone you need to keep an eye on anyway.
#13
It'll be ok until you want to transport it somewhere - which I'd assume maybe you will given your the sort of guy who has spare 412s sitting around his apartment . Having it open like that is just asking for trouble when lugging and loading.

Impedance notwithstanding, putting a couple of your V30s in the combo seems the best complete solution here. Or chop down the combo box into a head. Might end up looking a bit rough but let's face it .. no rougher than an open chassis.
#14
Quote by Roc8995
I

"If you touch something" is like saying "if you shove your hand into a bandsaw."



and wouldn't you know it that type of injury is pretty damn common around the world...plenty of darwin award candidates walking the planet
#15
For years I ran a full stack from a 1x12 combo amp that was simply on a tilted amp stand (On-Stage RS 7000) a bit in front (and slightly to the side of) the stack. Doesn't really matter much if you block a part of a speaker or two. Fact is, you could put the 4x12 on the stand (it'll handle up to 150 lbs) and put the 2x12 on the ground right in front of it and that would work as well.
#16
Quote by sytharnia1560
and wouldn't you know it that type of injury is pretty damn common around the world...plenty of darwin award candidates walking the planet


Such injuries are common in my line of work - agricultural research - including myself. It happens because fast moving parts are invisible - just like electricity.
#18
I highly suggest getting a head enclosure of some sort to protect the chassis and yourself. While the likelihood of someone getting fried is pretty low, the consequences would be dire. From the two or three amps I've taken apart (I'm more of a guitar guy than amps -- too scaredy of a cat) I'm willing to say that I don't think transportation would be safe considering held voltage. It would be altogether too easy to wrap a finger or two or four around the edge and into the wiring. If you were never going to transport it without gloves or with two hands you'd be okay though. I still wouldn't recommend risking it. The best option seems like swapping two working speakers into the combo and either selling the other two or waiting until you can get an enclosure made. Combos are also a lot more convenient for moving around.

#twocents (are the youth still using hashtags?)
#19
Quote by slimjimmypage
I highly suggest getting a head enclosure of some sort to protect the chassis and yourself. While the likelihood of someone getting fried is pretty low, the consequences would be dire. From the two or three amps I've taken apart (I'm more of a guitar guy than amps -- too scaredy of a cat) I'm willing to say that I don't think transportation would be safe considering held voltage. It would be altogether too easy to wrap a finger or two or four around the edge and into the wiring. If you were never going to transport it without gloves or with two hands you'd be okay though. I still wouldn't recommend risking it. The best option seems like swapping two working speakers into the combo and either selling the other two or waiting until you can get an enclosure made. Combos are also a lot more convenient for moving around.

#twocents (are the youth still using hashtags?)

put this on your vagina
#20
I would never run a tube amp outside the case except for when working on it, too dangerous. That's about like running a Skil saw with the blade guard tied back, asking for trouble. There's a guy running around somewhere in Texas right now missing 4 toes for that reason...and my uncle specifically told him to NEVER run the saw with the guard disabled...

Put the amp beside or behind the cabinet, that will work well, that's how Eric Johnson runs one of his Marshalls. I've done the same before, put the amp behind the cabinet for reasons of cramped space.

You can also transfer 2 speakers to the combo cabinet, but make sure the impedance will match. Tube amps do not like speakers below the impedance rating of the amp. You can run 8 ohm speakers in a 4 ohm amp with no problem, but not the other way around, that can blow a transformer...last one I bought was $125, around 15 years ago. It was not speaker impedance that blew it, different problem.

Check the impedance rating of the amp. Being a 2x12 it's probably 4 ohm. Check the impedance of one speaker from the 4x12 cabinet. If it's 8 ohm you're in business. Two 8 ohm speakers wired parallel will give you 4 ohm impedance, just what a 4 ohm amp likes. If they are 16 ohm, parallel wiring would get you 8 ohms, still ok for a 4 ohm amp but it will work a little harder.

Here's a good site for simple wiring diagrams

http://www.eminence.com/support/wiring-diagrams/