Now that I've got my test equipment stuff all sorted out, there's one thing I need to build before I can test audio amplifiers, and that's an Audio Dummy Load. Similar to the Dummy Loads, or Dummy Antennas, that I use when testing transmitters, but specialized for audio use.
It's basically a Load Bank of non-inductive resistors with some "5-Way" binding posts, and it will allow me to run just about any amplifier I'll ever have to test.
The green things are 8 Ohm, 100 Watt resistors, and are connected in series/parallel to give me 8 Ohms at 400 Watts.
The brown board is a cut-off piece of the flooring we just had installed that I kept a few pieces of. It's non-conductive, easy to drill, and best of all, FREE! The two red and one black items are the binding posts, and I'll drill the piece of aluminum angle to use as a bracket. One will be the common, one will be for 8 Ohms, and the third will be for 4 Ohms. By tapping the junction of the four resistors, I'll have a 4 Ohm load rated at 200 Watts, and that should be plenty.
Why a dummy load? Well for one, I don't have any speakers that can take that power level, and two, it would deafen you in the shop.
Good practice to have that item in an audio repair shop. However, are speakers actually 8 or 4 plus j zero impedance? I don't know much about that end of the electromagnetic spectrum.
ReplyDeleteThey're all over the map, depending on many things. "Common Wisdom/Tribal Knowledge" says to use non-inductive resistors "just in case". I gave my Impedance Bridge to the guys on the Iowa because I never thought I'd get into audio at this level.
DeleteOh, well.....
Improvise, adapt, and overcome... ;-)
ReplyDeleteThe only things I had to buy were the resistors.
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