PLASTIC BOXES AS ENCLOSURES?

[zener]

I've always read that a metal (usually aluminum) box is recommended as enclosures for stompboxes. I can get a lot of plastic boxes which sizes are suitable for enclosures. I'm just wondering if I can use them as enclosures? What should I do so that those can work like aluminum boxes? (coating inside?)  I'm not really worried about the strength of the plastic since I'm not a heavy stomper and my future stompboxes will be used mostly for practice.

Another question:

It seems easier to find ICs than transistors here in my place. I experienced travelling from 4 different stores covering several kms. (Radio Shack here is useless) to find some transistors (J201 and its substitutes, 2N5088 and 89) and went home not having one :x . Just recently, I finally found a 2N5484, a J201 substitute . But since it's just a substitute, I still don't feel confident about it until I put everything. (for Insanity Box, actually)

Any DIY stompboxes without transistors (there might be few), preferably distortion pedals. Dist+ and Smash Drive are already in my list.

Thanks for any help :wink:

[ExpAnonColin]

About the plastic boxes:  It's all a matter of taste.  I've done both, and plastic is a bit hard to paint, and covering the inside with aluminum (which is almost necessary) is sort of a pain.  It's easier to drill though, but it doesn't feel as sturdy.

In terms of distortion boxes without transistors, I'm sure there are a few...  Ansil has the "simple hate" box on his site that only uses a LM386. (I can't seem to find it, but basically it's just the LM386 with no capacitor in between the 1 and 8 pin, then 2 assymentrical diodes at the output)

Remember that you can always order online if need be.

-Colin

[Paul Marossy]

The only disadvantages to using plastic for enclosures is that the material is much weaker and they will not positively prevent EMI from getting to your circuit unless you shield the inside with copper or alumium tape. I have built a couple of things using plastic enclosures, but they were not things I would step on to switch and I shielded the insides w/ aluminum tape, making sure that the input and output jacks were physically touching the aluminum shielding. It doesn't do much good to have the shielding inside if it is not grounded.

[petemoore]

for the stompswitch on the outside of the box and you may be able to increase it's 'weightworthy' stompswitching ability...but if the washer doesnt distribut the stress evenly it could be worse than having none

[Fret Wire]

Paul's right with the shielding. Also, use tape with conductive adhesive, or every where you overlap the tape, you have to use a small tack of solder to maintain a continuous ground. You shouldnt measure any resistance from any point inside the box. Stewart-McDonalds has the type of copper tape I'm talking about. I've done plenty of Strats, and it works well. Also, shield right over your drilled holes, then cut out with an exacto knive. Then your jacks and pots will be grounded.
Paul, now having said that, I'm getting ready to put together my first pedal, a dist. + clone. Has anyone tried shielding an aluminum box? Is it worth the effort? It seems that on stage, where there are alot of interference sources, it may make a difference.
I know it couldn't hurt to try, but I use copper tape on guitars, and the paint would be the way to go on metal boxes. The paint is expensive compared to the tape.  I guess I could shield my first one with tape, and it it works, go with the paint.

[smoguzbenjamin]

To make a long story short: better to invest in aluminium boxes.  

[Mark Hammer]

As big a fan as I am of the 1590B and BB, I've been using plastic enclosures more and more these days, largely because I have a bunch I bought for a buck a pop (although the surplus place caught on and hiked the price to $2@).  These are very sturdy Pactec boxes in a kind of textured beige plastic, offering pretty much the same real estate as a 1590BB though with slightly different dimensions and layout constraints.

Obviously shielding is an issue, so I do two things to help keep stray stuff out of my signal path:

1) I make the end pieces that fit in the slots provided out of copper-clad board.  It's easy to cut to shape and provides a nice continuous ground plane connecting the power and signal jacks.

2) I cut out a piece of copper shim, which is held in place against the upper half of the case by the pots and switches.  The shim is nice because you can solder to it easily, so I can run ground leads from the end pieces and pots to the shim piece as a ground plane.  It is rare that sources of EMI/RF are going to come from below the pedal, so simply shielding the top surface goes a long way (if imperfectly so) towards providing the shielding equivalent of a metal box.

The other thing I try to do is situate the stompswitches near the edge of the chassis so that the structure remains as rgid as possible when stepped on.  If you download the Woody.zip file at my site (http://hammer.ampage.org) and unzip it, you'll see some pictures of a pedal made in one of these using the techniques described.

Although I don't do it as much as I could or should, using shielded cable is probably a good idea too.  It is worth noting that plenty of companies have used plastic cases without incident, although my guess is that customers are more assured by a metal case.