Boxing it up

If you are building an effects pedal, you are likely going to need a case, or enclosure to keep it in. Let’s face it, the varying names and colors on the boxes are often the only differences between certain types of pedal anyway.

 

The gold standard for containment in the pedal biz is the die cast aluminum enclosure from Canadian company, Hammond Manufacturing. Drilled and painted Hammond boxes provide the exteriors for the majority of boutique pedals, but that is by no means the only way. Let’s take a look at the benefits to keeping it standard, and some fun options if you prefer to go it alone.

The Hammond 1590 Series is the baseline for effects pedals. When someone says they are using a 1590A or BB style enclosure, these are Hammond part numbers. Even though we might actually be using a box manufactured by another company, it’s often the Hammond part numbers we reference, a sure sign that they have become the de facto standard. Other manufacturers make similar enclosures. New Sensor is owned by the same people as Electro Harmonix, so that will give you an idea of the types and choice of enclosures they have available. Eddystone enclosures out of the UK have been part of Hammond Manufacturing since the late nineties. There are also various far east manufactured boxes available from specialist pedal parts suppliers such as Small Bear Electronic and Pedal Parts Plus.

A major advantage to using genuine Hammond boxes is the quality of support. Detailed documentation with accurate measurements is provided, as well as well as 3D files in multiple formats. This may not be a requirement for the hobby builder, but it’s important for the commercial manufacturer that uses CAD and CAM tools to speed design, and produce a consistent quality product in volume.

Die cast aluminum enclosures are strong and not too heavy. They can be easily drilled with low cost tools for home projects, as well as consistently machined on a production line for volume manufacturing. They provide a good substrate for finishing with paint and fixing with adhesives. They stand up well to knocks and scrapes, and can be expected to withstand many years of heavy use. These are all good reasons to use this type of enclosure for your pedal.

Production of die cast enclosures requires custom tooling. Molds are created for the parts into which the molten alloy is injected using special machinery. Creating these molds is very expensive, and they have a finite life. All the stars have to line up to make selling such enclosures commercially viable. As a result, there is a fairly limited range available, and they are the same ones as everyone else uses. Differentiating the appearance of your product can be a challenge with the limited choice.

Die cast enclosures respond well to painting in both liquid and powder. Alternatively, they can be engraved using moderately priced tools. Decals and different types of adhesive label can be applied. A friendly local trophy store can be a great resource for the pedal hobbyist. Most moderate sized towns, in the US at least, normally have one or two in the neighborhood. These stores will usually have laser cutting and engraving tools, and a range of different label materials. They will be happy to make one off or small runs of custom adhesive labels that can give your project a professional finish at a reasonable cost.

Anodizing is an electro-chemical process that creates a protective coating to non-ferrous metals, particularly aluminum. In combination with certain dyes, the process can yield a distinctive finish with excellent cosmetic qualities. Unfortunately, being a chemical process, the quality of the result is very much dependent on the makeup of the base material. Die cast aluminum products are usually alloys that are not suitable for anodizing. Other elements are added to the aluminum to provide certain properties, in particular Silicon is added to improve fluidity. Silicon does not anodize, and the result is normally a dull and patchy finish. There are potentially ways around this but they are complex, expensive, and normally reserved for industries such as aerospace and professional sports where the budgets are somewhat higher.

For an anodized finish, you’ll need a folded aluminum enclosure. A few of the specialist pedal parts stores are offering some of these now. If you are into mechanical design you can create one fairly easily, and it’s a good first project if you are interested in learning. There are several free or low cost 2D and 3D design tools that have recently become available like SketchUp, and Autodesk 123D. I use Draftsight for 2D. Check to see if you can find a local metal shop that can fabricate your enclosure from your drawings.

Anodized finishes can be laser etched. It’s great for small text or intricate graphics as it provides a very high resolution with sharp edges. It’s only one color though, and the color is determined by the chemical make-up of the oxide, so you don’t really have much control over it. Screen printing over anodized parts is common for commercial products. The oxide layer is non-conductive, so if you need the enclosure to act as a screen, you’ll have to have a conductive layer applied first. You’ll need to see of your anodizing shop can support this, and it adds cost.

This leads us nicely on to screening, and the contention that a pedal enclosure must be bonded to ground. I’ve seen plenty of times comments or complaints about pedals from various sources that do not have the chassis connected to the circuit ground, but there is really no rule that says this is required, and in some cases it may actually be necessary to isolate them. Take a look around at some of the electronics you have where the enclosures are wood, or plastic, or some other insulating material.

If you are using a metal enclosure, connecting it to the electrical ground is often done so that the chassis functions as a shield against electromagnetic interference. In low voltage DC devices such as most effects pedals where the – and ground are usually common, connecting them all together can often help both protect against noise induced from EMI, as well as radiating EMI causing noise in other devices. However, this may not always be the case. Think about it, guitars and speaker cabinets which are effectively enclosures made of insulating wood or plastic, work perfectly fine without a ground bonded metal chassis, although it is true that the EMI performance can sometimes be improved by correctly adding some metal shielding to these.

When using intentional radiators such as wireless devices, enclosing antennae in a grounded metal box will pretty much stop it working at all. We are already starting to see wireless features such a Bluetooth getting added to effects units and digital amps so we can expect this to become more commonplace as effects become more sophisticated.

So it’s certainly not a requirement to make effects pedals in small metal boxes. If you are handy with a saw and hammer, making a wood case would be perfectly reasonable. If it’s a gain pedal and gives you problems with EMI, then you can use some adhesive conductive metal tape on the inside of the enclosure. The same goes for plastic, and using an off the shelf molded plastic case, or making one yourself from acrylic or polycarbonate would be feasible. Since these materials are available clear, you can even show off your electronics handy work.

And while using square and rectangular boxes maybe the most practical from a build and pedal board layout standpoint, there’s really no reason that has to be the case. If you are looking for some inspiration, look no further than the Dr. No Effects Ford Falcon Fuzz, a fuzz pedal in a toy car. Yay!

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