Shielding a Cab Chassis Worth It?

[The New Steve H]

I just built my first big head cabinet. Got a couple of questions.

The amp chassis has no bottom. Is it worth it to close it in so it will be shielded? It would be a giant pain in the butt, but I can do it if necessary. I am wondering if shielding paint is a viable option.

Also, do people generally close up the backs of head cabs? Right now this one is wide open. I was thinking I might put some wood in the back, but I would have to leave the upper half pretty much open for cooling, and I will have to be able to get my hand in at the bottom because that's where the fuseholder is. I guess I could rig it up so the back comes off with screws.

I haven't put the handle on top yet. I'm planning to mount it off-center because the weight is all on the right side of the amp.

I still have some tidying up to do, and the faceplate has to be done. I learned an awful lot about upholstering while I was doing this job. Mostly I learned that I suck at it.

[M Fowler]

That looks good.

You can put a small strip of wood in the center of the back to keep hands out.

You may not need a bottom plate I often don't use one. You could use aluminum tape on the bottom of the cab.

[The New Steve H]

Thanks. I can't figure out how to do inside corners with upholstery. I will probably have to fabricate some kind of aluminum pieces to cover the corners over the knobs. I can turn a 7/16" aluminum cylinder and leave a flange on it. Then I can cut two quarters out of it and screw it into the corners, through the flange.

Tape would be a lot less aggravation than cutting a sheet.

I'm starting to like the thick chassis. It has its drawbacks, but it will be impossible to damage.

I didn't realize metal corners wouldn't work with 1/2" plywood. I guess I could make some smaller ones.

[Reeltarded]

Steve, throw a shield in the bottom of that bad boy, and I swear if you mess up the retro-awesomeness by changing a thing I will delete the internet.

That is very cool lookin'!

[The New Steve H]

Wow, thanks. I'm planning to put a fake gold-tone engine-turned faceplate on it, and I had to put a handle on it, but other than that, the front is staying the way it is. I thought the lizard vinyl was overkill, but it's working out.

I'm looking into a nameplate with retro fonts.

I'm amazed at how good it sounds. Someone should give Da Geezer a medal.

Here's a new question. I have a little bit of high-pitched hum. It's not 60 Hz. It goes away when I touch the chassis. What on earth does that mean?

I guess I could play with one elbow against the chassis.

[Reeltarded]

Yeah 120hz.. I wonder.

Have you ever done a hum test with a big , heavily taped up screwdriver?

Wrap everything but the handle in 2 layers of electrical tape, and hover over everything in there slowly. Those kind of noises generally get loudest right before you actually ground to it.

You know, electricity tastes great, but don't eat too much.

[Phil_S]

Cut a sheet of heavy duty aluminum foil to fit the bottom of the cab. You know, the stuff that's found in the kitchen. Smear the bottom of the cab with Elmer's or whatever is on-hand. Rub the foil onto the Elmer's. I use a rag to do the rubbing 'cause I don't like rubbing the foil with my hands -- almost no friction with the rag. For 10 cents, you can have a perfectly good shield, and you need it whether you know it or not. Don't over think this. No one sees it.

[Gibsonman63]

Great looking cabinet. It reminds me of the really early Marshalls... on steroids. A side shot would be nice so we can admire the lizard print.

When I built mine head cabinet, I started with the corner protectors and contoured the cabinet to match.

Do you have the hum without anything plugged into the amp?

Have you checked all of the input jacks to see that they short when there is no cable plugged in?

[Reeltarded]

Oh, dumb me..

Steve, shield,then complain about hum..

[The New Steve H]

Is the shielding paint a stupid idea? The reason I ask is that I already have it, and it would match the black lizard vinyl.

Whatever I do, it will not be perfect, since the ends of the chassis are open.

I don't know if it hums with nothing plugged in, but I'll check. I figured this level of noise was more than acceptable, until I found out I could make it go away.

I appreciate the compliments on the cab. I would have been happy with "not horrible."

[cbass]

cool! diggin the gold knobs

[Reeltarded]

I love it. Get out the tools, cap the ends and put a simple plate in for shield.

I am betting NO hum then, or not much at all.

You made that JTM tranny fit, Mr. Metal... don't stop now! Really like this amp. It's classic lookin'.

[Gibsonman63]

Fender's blackface approach was to staple a thin sheet of metal to the inside of the cabinet. When you snug down the screws, everything makes contact.

The silverface approach was to use screen, but it may be difficult to source conductive screen these days.

[Reeltarded]

Yeah, simple roofing flange material that you could cut with your best set of Fiskars from Home Depot' (that's French! I am intercontinental or something!) works. About the same material Fender used. You could cut end caps and a bottom plate in about 10 minutes, and fit them in 20.

If you try to be lazy with it, you'll only create more work. lol

I know this. I am lazy, and work extra hard for it. Darn.

[patrick620]

Thanks. I can't figure out how to do inside corners with upholstery. I will probably have to fabricate some kind of aluminum pieces to cover the corners over the knobs. I can turn a 7/16" aluminum cylinder and leave a flange on it. Then I can cut two quarters out of it and screw it into the corners, through the flange.

Tape would be a lot less aggravation than cutting a sheet.

I'm starting to like the thick chassis. It has its drawbacks, but it will be impossible to damage.

I didn't realize metal corners wouldn't work with 1/2" plywood. I guess I could make some smaller ones.

This link below might help with the inside corners. Great looking amp, btw. As you have obviously learned, most amp corners (I use two hole w/inside lip) work with 3/4" material with a 1/2" roundover bit. Most always I also have to use a "rat tail" file to make a small notch on the inside corner for the lip. Especially after adding the tolex. Sometime you can use a hair dryer to make the fabric more pliable to close any gaps. Or you can get a "tolex stretcher" at HD. It's on the same aisle with the wire and concrete stretchers.


http://guitarkitbuilder.com/content/how ... er-cabinet