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Old 2nd December 2006, 10:02 PM   #1
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Default What do you use for a simple cheap load?

I once saw a page where someone used an array of 25 watt bulbs, but lost it. What are some suggestions to build a dummy load that can sink maybe 200 watts to warm this critter up?
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Old 2nd December 2006, 10:41 PM   #2
Chartal is offline Chartal  Canada
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Look at Part Express
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Old 3rd December 2006, 09:10 AM   #3
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A lightbulb is about the worst thing you could use to load an amplifier with. The resistance changes at about a 20:1 rate, being close to a dead short when cold.

Find some cheap resistors surplus, and wire them in series/parallel as needed to get whatever impedance you need.
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Old 3rd December 2006, 09:24 AM   #4
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Something like this?

4 x 2R 50W each side.
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File Type: jpg mydummyload.jpg (88.6 KB, 742 views)
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Old 3rd December 2006, 10:26 AM   #5
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http://www.skycraftsurplus.com/index...ROD&ProdID=896

Very cheap load resistor. Needs to be heat sinked.
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Old 3rd December 2006, 10:33 AM   #6
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I used to have a 500W voice coil from an old 18" driver. I hung it in a pot of oil and it worked well.
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Old 3rd December 2006, 09:36 PM   #7
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How often do you change the oil? And are the french fries up to the level?
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Old 4th December 2006, 06:32 AM   #8
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Default The voice coil, inside oil, having its own magnetic element will be unbeatable


Only a real speaker, installed in a tuned duct housing will perform better as a load...because real load.

That coil is almost a real speaker..having normal inductances, resistances and capacitances....this way the reaction produced (EMF) is almost the same we have with speakers.... will loose the ressonances and this is something not good, as you will not measure, you will not observe the waveform that results of this normal sittuation.

Resistances are not a good load to amplifiers...as they are far away from the real condition the amplifier will works.... some resistances are so good, as resistances, that will have low inductance and low capacitance and this will produce a fause measurements of your amplifiers...the amplifier will measure much better than the reality..... fake measurements and wrong specifications will be produced.

I think that nothing can be better than a simple solution.... if you cannot use a real speaker with full volume under tests.

It is good to remember our friends Pinkmouse, that they cannot use the coil without the magnetic core, because it will burn in flames with 10 watts when normal power coil is used (100 IHF watts speaker coil... something alike 30 Watts continuous)

I feel myself very happy when i face those simple and perfect solutions.... something that simulators cannot make under real conditions as we cannot plug "that coil" in the computer communication's port.

regards,

Carlos
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Old 4th December 2006, 07:34 AM   #9
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Smile try to get some bit of reality into your numbers, PLEEEEASE!

.

I agree to Carlos point of view.
By the 107.33% level of pure non distortion!


Now there are different kinds of simple solutions for power resistor loads.
We have some low inductance specially made power resistors
made for 'pure resistance' tests loads

They have often the wire bi-filar wounded:
- that is for every wound one way they change direction
and wound one turn the opposite way
and when doing so, the inductances are more or less canceled .
They take out each other producing much lower inductance
although it is a wire wound resistor still.


Now normal standard power resistors
have all turns going same way, as in a coil.
This makes 'normal' Power Resistors have an inductance.

Even if this inductance is not to compare to a speaker or crossover inductance
.. it is step in the right direction of a real load.


So go for normal wire wound inductive power resistors in testing loads.
For power amplifiers output at least!

And the very good thing is
... they are the most low cost Power Resistors
we can find.

lineup
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Old 4th December 2006, 03:21 PM   #10
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I was thinking maybe my old coffee pot or something! :^)
I have an old coffee roaster that has many turns of nichrome wire.
Just have not got around to measure them yet.
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