Building a Head Cabinet.......Grounding, Shielding questions

[Mesa Boooogie]

Hi everyone,

My first post on a forum that looks infinitely packed with lots of great guys and lots of answers.

So, here's a question: I recently purchased an '87 Mark III Red Stripe (60-watt w/ EQ) which was in the 1x12 combo form. I didn't want a combo but it turned out to be a great deal on an amp I wanted. All told it was about $650.

Anyhow, today I put together a simplistic version of a headshell. No interlocking finger joints or exotics wood. Just something I can put the chassis in and get a cool look with. After doing a bunch of scouting it seemed like there was no getting a hardwood cab without spending almost as much if not more than I spent on the actual amp itself. I figure, from 15 feet away it'll look about the same and save me a pretty penny. Besides, if I ever want a real-deal Boogie cab, they're always for sale.

Anyway, here's the question. I noticed that inside the combo enclosure there is a silver, metallic foil which seperates the components within the chassis from the top of the cabinet. there appear to be two other wires running to two of the screws that hold the chassis in place. I figure this all has something to do with shielding the components and quite possible some sort of ground issue based on the wires leading to the screws.

In any case, I'm no electrician so I'm not going to do anything without some solid advice. I was hoping someone could tell me what the foil and the two wires do within the combo and if they need to be replicated inside the headshell I built today.


Oh, and where can you purchase wicker a la all those classic Boogies?

Thanks so much in advance!

 

[Buddy]

The foil is there , as you have guessed , the shield the amp from nearby noise and interference .( like if you stacked other equipment on the head , etc.) The little braid jumpers are there to keep the foil at the same electrical potential as the rest of the chassis . Hold the extra capacitance , please .
It will also shunt any noise to ground .
I imagine you could duplicate it with some foil and spray glue , etc.
Our friend's in Petaluma do stuff like this for good reason .
Lotsa luck !

 

[Elpelotero]

http://www.vibroworld.com/parts/tech10.html

 

[Blueracer]

I am retoring a iic+ and instead of the foil I decided to use a piece of sheet metal as a top to the amplifier to prevent interference. I thought the foil was a bit cheesy. The foil was half ripped out when I took the amp out of the cab. I got the idea for thisl from my Traynor amps which use the sheet metal method as opposed to the tin foil in the top of the cab. Here is a picture.

I bought the sheet metal at Home Depot and took it to a local sheet metal company to cut to size. Drilling the stuff is tricky as the bit will grab the material and twist it. I ended up drilling using a small bit then filing the hole to size. This may be a bit of over kill but it worked for me and turns out very clean. You do have to make sure that the screws that attach the cab handle don't protrude into the sheet metal. If they do just shorten them a bit. I had a little bit of filing to do there or you could cut with a hack saw.

Hope this helps.

Gary

 

[Blueracer]

For shielding I wonder whether aluminum flashing would work. It comes in rolls of various widths. If it'd work as a shield.... cut to length, dress the edges, and glue into place with contact cement.

I don't see why flashing wouldn't work. The one thing I was concerned about was the non-similar metal thing leading to corrosion where the two metals met. In order for this to occur though you need moisture. This is a consideration but a minor one I would think. Other than that I would think flashing would work fine.

 

[Mesa Boooogie]

Thanks a lot everyone.

Today I was able to get the structural components of the headshell pretty much done although there are still a couple things I'm contemplating cutting a bit shorter.

Anyhow, I went with the foil shielding for now since it was available and easy. The amp shouldn't be near anything for now. Of course, if it doesn't fulfill its purpose completely or I feel up to it I can try something else like the nice sheet metal idea presented. That looks smart!

I also went all over town looking for the wicker cane material which I didn't find. I was able to track down some online sources thanks to you fine folks and a few searches on the forum. It looks like I'll have to just go ahead and order the material via some website.



Does anyone know specifically what "open weave" dimension to order the wicker in? There are options such as 3/8", 1/2" and 3/4" open weave.

Here's a link to what I'm talking about:

http://216.105.59.114/index.asp?PageAction=VIEWPROD&ProdID=59