For a very long time now, people have wanted to make plate amps for subwoofers, in-built amplifiers for powered PA boxes, or custom in-box amplifiers for hi-fi systems. While all of these were possible, it usually required complex metalwork to get something that had sufficient heat dissipation yet provided a flat rear surface and somehow integrated an off-the-shelf heatsink.

With the release of ESP's custom extrusion, this has become a simple task. The heatsink is designed to accept a standard 3mm thick flat aluminium panel to give the mounting area for inputs, controls, mains socket and switch, etc.

It is an ideal section for many applications - spectacular car amplifiers can be made using the ESP heatsink and standard aluminium extrusions. Also suited to 'tower' amplifiers, power supplies, industrial power controllers, or anything else that needs an easily mounted flat-backed heatsink. When you examine the photos and drawings, it will become obvious that I have only scratched the surface of the many ways the extrusion can be utilised.

Figure 1 shows a 300mm length of the extrusion. This has been tested to determine the thermal resistance, which is 0.7°C/W (at 70°C) with no additional panel, and in the natural aluminium colour. If anodised or with a thin coat of matte black paint, the thermal resistance has been calculated to be around 0.3°C/W. The side panel (see below for more details) forms part of the heatsink, and will reduce the thermal resistance further. The performance increase can be substantial, depending on the size of the side (control) panel.

Figure 1 - Side View of Heatsink

In figure 1, you can see the recess for mounting the flat plate. The heatsink also has a flange (see Figures 2 and 3), which also fits perfectly into the recess, allowing heatsinks to be joined together to make a larger section.

Figure 2 - Other Side View of Heatsink

The flange is visible above. The main purpose is to provide a surface for mounting screws, but as noted above, the flange will also mate with the notch on the other side.

Figure 3 - End View of Heatsink

Here, you can see both flange and recess. With an overall width of 95mm, if two sections are mated together you get a heatsink 175mm wide. Because it is a custom extrusion, it can be supplied in any length (see below). The transistor mounting surface is 5mm thick, and being an extrusion it has excellent thermal conductivity.

Australia seems to have a better than average range available to the DIY fraternity compared to other countries, but of those available, some are cast (which tend to be rather heavy), and some others have a base that is too thin to disperse the heat to the fins effectively. Others are unsuitable for any application where cosmetics are important (and are usually only available in rather small fixed lengths unless you order a large number).

Figure 4 - Extrusion Dimensions

These are the dimensions of the heatsink. The nine fins are 10mm apart (between centres).

Figure 5 - Heatsink & Panel Assembly

The arrangement shown above will be perfect to make traditional subwoofer 'plate' amps, or amps for installation into PA or hi-fi speaker boxes. With a 300-350mm length of heatsink, the flat panel can be made as wide as needed to fit everything onto the rear, and is very much the equal of any plate amp extrusion currently used, but with much greater flexibility. For larger amps, the arrangement shown below will be perfect.

Figure 6 - Double Heatsink Panel Assembly

As shown above, it is an easy matter to attach a 3mm plate to the recessed area, and another section of heatsink can be used on the other side of the plate if more heatsink surface is needed. This assembly is designed to accommodate a pair of high power amplifiers for large subwoofer systems. If one were to use a pair of heatsinks 400mm long with a 100mm centre section, this is a very potent heatsink indeed. With plenty of room for transformers, mains and signal connectors, switches, etc., it could easily accommodate a pair of P68 amps for example. In the single board version, this allows a comfortable 600W (2 x 300W) into a pair of 4 Ohms subwoofers.

Alternatively, the same arrangement may be used to build a compact 3-way active speaker amplifier.

As an example, a 40mm length is ideal for GainClone type amps, and will look very stylish (although it is a bit on the small side for full power). This size also fits inside a 1RU case (these are 1¾" or 44.45mm external). ESP offers the following standard lengths ...

The basic price structure is based on AU$ 0.60 / centimetre (10mm), plus a fixed AU$ 2.00 per length ordered. Within Australia, GST needs to be included, taking the price to $0.66 / cm + $2.20.

All prices shown are for 1-4 pieces, and discounts apply for larger quantities - contact ESP with your requirements. Exported material is not subject to GST, hence the lower price. Lengths marked with an asterisk ( * ) are likely to be the most popular, and will be kept in stock for immediate delivery.

Custom lengths will also be available at the same price as those listed above. In all cases, to get a good price you will normally require a minimum order of 10 pieces. There will be a typical delay of around 2-3 days. Custom length pricing shown above is for less than 10 pieces. All lengths are subject to a tolerance of ±1mm unless you specify otherwise (a surcharge applies for very close tolerance machining).

The price is the best part! Relatively small heatsinks from the normal electronics suppliers cost a great deal more than indicated above. Custom lengths are extremely difficult to obtain. Since ESP can supply any length you need for only $ 0.60/cm + $2.00 cutting charge (+ GST within Australia), a 375mm length (for example) will cost AU$24.50 + GST (less for 10 or more). Each piece will weigh in at about 720 grams.

Please note that ESP's standard postage rates do not apply to these heatsink sections. Because of the weight and size, even small sections must be sent as a package. Before ordering, please contact ESP with your requirements (length and number of pieces), and I will calculate the postage based on your purchase and location. Postage will be charged at the current Australia Post rate, plus a packing charge of AU$ 5.00 for each order.

You can get a reasonable idea of the postage cost by visiting the Australia Post website. I have included an example below, so you can get a fair idea before you order. A pair of 200mm lengths weighs 770 grams (about 870g with packing), and will measure (approx) 220 x 100 x 50mm

If you also require PCBs (such as P68 or P3A), please order at the same time, as you will save additional postage costs. The boards can be packed along with the heatsink, and will add very little extra weight (and no additional postage cost if the entire package remains within the weight range). For example, airmail packages are priced in increments of 250g ... one gram over that, and you are in the next price bracket. For the example shown, you can add 130g of PCBs free of additional postage.

1. Total includes AU$5.00 packing charge, and also includes GST for Australian purchasers
2. The above is an example only. Please do not assume that your order will match the above - it may be more, or it may be less. Airmail rates are quite variable, and it simply isn't possible to provide all the alternatives.
3. The maximum weight of an airmail package is 20kg - you don't want to know the cost for that !
4. Sea mail is cheaper, but also takes a long time. For some orders, international couriers may be a cheaper alternative, but this has not been investigated at this stage.

If you are a manufacturer or reseller and want larger than normal quantities and/or lengths, please contact ESP for a quote. The maximum length is 4m, but this cannot be sent via post. Full lengths (4m) are pick-up only, and can only be supplied within Australia. Very large quantities (either as full lengths or cut to the exact size needed) can also be arranged by prior arrangement anywhere in the world. ESP can supply all necessary details upon application.