EZLoad : A High Power Dummy Load


Project Resources
EZLoad Gallery Hammond Chassis Hammond Chassis Cover DIY Audio Thread
Project Notes

The EZLoad Project is a versatile high power dummy load for testing high power audio amplifiers. I picked up some 4 ohm 200 watt resistors off of eBay for about 20 bucks. The were imports and not very expensive given they style and wattage. I had a spare 6″x10″x2″ Hammond chassis from the EZ10 project and fit it all to that size.

My previous load was 4 20watt resistors sitting on the bench with some scrap wire connecting the mess. At some point during my inclination to build the EZ125 amp I figured I would need to build the EZLoad.

IMAG1642The design was done with 4 x 200 watt resistors mounted to an aluminum plate which was mounted to the chassis. Most was automotive scrap aluminum I had in the garage. The metal was chopped up on my small cold saw and I used an excess of fasteners to hold things together.

The chassis was primed with a self etching primer then painted with some copper colored texture coat similar to the EZ260 amplifier as I had some extra paint left. The chassis cover was primed and painted satin black on the inside and out.

IMAG1671I also found a small quiet fan that I placed in the chassis just so I could add an toggle switch and power cord to the project. I had purchased this fan maybe 20+ years ago at a hamfest and it has survived many years in the parts bin. It’s happy (and so am I) to find it’s way into a project after this long and finally get some use out of it!

Each binding the set of speaker connections (or pair of banana posts if you will) are connected individually to a 4 Ohm 200 Watt resistors. This allows for the following configurations –

4 Channels 4 Ohms @ 200 Watts/Channel

2 Channels 8 Ohms @ 400 Watts/Channel

1 Channel 16 Ohms @ 800 Watts/Channel

While I doubt that I will ever run into or build any amplifiers that run into the need for this much power, it’s nice to know that I will never run into a problem with heating up the load while testing for any length of time. Overkill, yes, but also nice to know it’s overbuilt.

Wiring was straightforward, each resistor went to it’s own terminal and the fan was wired to a switch then the fan. Now I guess I should have tossed in a fuse, but the fan is impedance protected, yeah, that it’s it.

Other then that I made a couple of copper jumpers for the binding posts to make it easy for the default 8 Ohm selection to be used. In retrospect I might had stacked the binding posts into a square so I would just use banana jacks to plug in either 4 or 8 ohms but not a big deal.

Now go build one of your own, and add your own features to it to make it better!

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