wooden enclosure

[Nikos]

Hey there, i'm new to the forum.. I'm also new to the stompboxes stuff. I'm living in Athens Greece and it's very difficult to find aluminium enclosures for pedals in any stores I know. And the shippings costs from ebay it's to expensive for one or two enclosures. So I'm thinking of wooden enclosure for my fisrt try. And here come the questions...
1. Can anyone explain me when & where to use chassis ground?
2. I read here http://www.diystompboxes.com/smfforum/index.php?topic=80914.0 about risk of RF interference with wooden enclosure, and you must lined the box with copper foil. Is there any more specificated info on this?

Thanks & sorry for my english!

[GibsonGM]

Hi Nikos,

You certainly can use wooden boxes, with good results!   There was someone on here a few years back who made great hand-made ones.

You will have to line the box, but you can use ALUMINUM foil instead of copper, which is MUCH less expensive!   

You need to tie your input and output jack grounds to the foil, as well as your circuit ground.  This will create a shield around your effect so you do not pick up radio noise.

I've built circuits into PVC end caps, lined with grounded foil, and it works fine.   I also line the pickup cavities and pickguards of Stratocasters this way, and make them much quieter on stage.  Just make sure the foil is continuous all around the box, and do not short out your PCB on the foil!   

Let us know how it goes.

[italianguy63]

Hey Mike-- I never gave that any thought... would aluminum Air Conditioning tape work?  i.e. stick to itself and conduct?

[Nikos]

tnx for the reply. When you said circuit ground you meant the dc ground? the (-) pole of the battery?

[Nikos]

someone plz??

[Zipporello]

yes, you're right.

remember: if you'll use DC voltage power supply, usually the ground (-) is external. 

[Nikos]

what do yu mean external? I will use a classic 9v dc psupply for guitar pedals

[amptramp]

A bit of advice - do not count on the shielding to be useful as a ground return with aluminum because it may not make reliable contact.  Even if you have the input and output jacks connected to shielding foil, they should be connected with wires as well.  I have an old, cheap Cort guitar which was very noisy because the level and tone pots had the ground lugs soldered to the pot outer shell and the shells were pushed down on the internal shielding foil to ground them.  After wiring the pot grounds together and to the output jack, the signal became wonderfully clean and a professional musician who played it afterwards considered it to be a fine blues guitar.  Pictures of what I did to the Cort are here:



The added ground wire is the yellow wire connecting the pots and the pickup ground.

[gjcamann]

Your situation may be a good reason to get creative. Go through the trash to find your next enclosure. Here's some ideas:
http://www.diystompboxes.com/smfforum/index.php?topic=64643.0
I've also seen people make them out of coffee cans, tuna cans, caned ham cans, lamp bases, old toasters.
Good luck!

[Jdansti]

Nikos-Welcome!

Most of our circuits are negative ground and very few are positive ground. Here's an example of a circuit using negative ground:  http://www.beavisaudio.com/techpages/StompboxWiring/.

The link above shows the board ground, metal enclosure, jack sleeves, and negative power all tied together (the metal enclosure is grounded through the jack sleeves). There are several options when using wooden enclosures:

1) Line the wooden enclosure with metal such as foil or metallic tape. All of the individual pieces of foil or tape have to have good connections to each other and your ground. It's more difficult to do this with tape, but the adhesive might be a low enough resistance to work if you overlap the pieces.

2) Some manufacturers that use plastic enclosures wrap the circuit board like a taco with a sheet that has an insulator on the inside, such as paper, and metal foil on the outside. A tab sticks out from the "taco" so you can attach a ground wire with a screw through the tab to the plastic.

3) Use an ugly metal enclosure inside of the wooden enclosure. Food tins or cans work well for this. I've made internal metal enclosures from cutting up a thin roasting pan (the kind you use once and then throw away or recycle) and stapling the sides. 

Whatever method you use, the metal lining or box needs to be electrically connected to the circuit's ground for the shielding to work. Also, since most pedal external power supplies are center negative and positive sleeve, use a plastic DC power jack if there's any chance that the jack's body will come into contact with shielding (or metal enclosure) to avoid shorting out your PS. Alternately, a metal power jack can be used if it is insulated from the shielding.

Good luck!

[GibsonGM]

Yes - you MUST have good contact all around.    I use Duco spray adhesive contact cement, believe it or not...and it KEEPS the electrical contact after drying!   Has been good for over 5 years on my Strat.    Aluminum tape will probably work, but make sure to test it for continuity.  This is very simple once you successfully do one - you will then understand exactly what's going on. 

And yes, the foil should be 'extra' to the circuit - use wires for all connections like input/output grounds.    It's just the safer way to do it.  I have had no problems in a decade of doing it this way.

I like #3 above, Jdansti - good idea, and a good way to use ugly containers you may otherwise overlook! 

[psychedelicfish]

Aluminum tape will probably work, but make sure to test it for continuity. 

Most aluminium tape works fine at 100kV+ but I'm not sure how well it would work at slightly less lethal voltages . Actually, from memory I got a beep from my continuity meter, so it should generally be fine. As for where to find it, I got some at the $2 shop down the road. You might be able to get some from a hardware store or anywhere that would sell air ducting and the like.

Buying parts online may seem daunting and expensive, but once you find the right places it's way cheaper. Tayda Electronics sells reasonable quality (good enough for most jobs) aluminium enclosures for reasonable prices, as well as tonnes of other parts for pretty cheap (WAY cheaper than terrestrial shops, anyway).

[Nikos]

tnx everyone! Everything was very useful. I'll keep in mind your suggestions & tips and experiment to see how it goes. I'll upload my final work, if any question comes out i'll post again!

[GibsonGM]

Good luck, Nikos!

Remember, Smallbear Electric is the place to get inexpensive real enclosures!  Just thought I'd put that out there since Psych.Fish mentioned it.  Smaller operation with a good connection to the DIY community (they contribute on here).   I've never had a single problem with their service.

But the challenge of making something really odd is great, too!