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Is this a good resistor to use with a completed Aleph-X amp to test power output and look for clipping behavior with a scope?
16 ohm 120w wire wound resistor
I was planning on getting 4 of them. I could put 2 of them in parallel for an 8ohm resistor and 4 of them in parallel for a 4 ohm resistor.
Thanks,
Eric
16 ohm 120w wire wound resistor
I was planning on getting 4 of them. I could put 2 of them in parallel for an 8ohm resistor and 4 of them in parallel for a 4 ohm resistor.
Thanks,
Eric
Sounds like a good plan. I have some of these myself, they're quite rugged and still go on happily after you have fried your whole hand trying to move them under heavy load
They may be very slightly inductive but for testing purposes that isn't an issue. How much power can an Aleph-X deliver, max, steady-state?
jd
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I'm building a set of them that will likely run 100wpc into an 8 ohm load and 150-160w into a 4 ohm load. Thus, putting multiple resistors in parallel will also boost their power handling capacity.
thanks!
Eric
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Do not forget capacitance across Rload...However I have not done this looking at my amps on the O'scope I have read it makes a difference in the scope pattern and is more like the actual load.
That being said good luck and let us know your results.Oh Yeah be careful those resistors get really hot, burning fingers do not feel or smell good...
Regards, Elwood
That being said good luck and let us know your results.Oh Yeah be careful those resistors get really hot, burning fingers do not feel or smell good...
Regards, Elwood
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The idea is that a real speaker load often represent a complex network not of just a resistor but also capacitors and/or inductors, and that even varies with frequency....
Especially the capacitive part can sometimes provoke an amp into instability/oscilations.
So, to check the power output of your amp in various steady state loads, the resistors are fine.
If you also want to verify amp stability, try paralleling those resistors with capacitors varying from perhaps 10nF through 100nF, 1uF, 10uF. Especially the latter is hard on the amp with high frequencies because it represent a low impedance, so you probably don't want to do that longer than just a few secs. Always slowly turn up the signal and watch the scope for funny patterns, turn it off if you see that!
Let us know how it goes!
jd
Mine are a bunch of Dale's that I bought at Electronic Surplus in Cleveland -- I use 5 50Watt, 40 Ohm -- mounted on a piece of spare pcb material. When I was testing the bridged LM4780 article for AX I accidentally placed the "tester" on a scotch tape dispenser -- and it melted the plastic onto my workbench.
Probably a good idea on settling on a connector scheme at the same time. While banana plugs are most frequent, you might also want to consider those times when you'll use pin plugs for old amps with those push-in speaker connectors.
Sometimes you'll see Heathkit dummy loads for audio on Ebay. I used a Heathkit "Cantenna" back in the ham radio days -- filled it with salad oil if I recall correctly. Oh, salad oil does go rancid after a while \m/
Probably a good idea on settling on a connector scheme at the same time. While banana plugs are most frequent, you might also want to consider those times when you'll use pin plugs for old amps with those push-in speaker connectors.
Sometimes you'll see Heathkit dummy loads for audio on Ebay. I used a Heathkit "Cantenna" back in the ham radio days -- filled it with salad oil if I recall correctly. Oh, salad oil does go rancid after a while \m/
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Just looking to the future, am I correct to assume that I should make adjustments to properly set the bias current and reduce any DC offset before I do power output testing with these big resistors?
As you can tell, I've never done this before and since these amps will be driving expensive speakers, I want to make sure I stress-test the amp on the bench first.
Thanks!
Eric
As you can tell, I've never done this before and since these amps will be driving expensive speakers, I want to make sure I stress-test the amp on the bench first.
Thanks!
Eric
Those resistor are a great find. Nice price. I use the fancy ones from Parts Express.
8 Ohm 100W Non-Inductive Dummy Load Resistor
They will also melt right thru plastic!
The other day I was looking for a dummy load that would take even more power. Found it. My little electric oil filled radiator heaters from Walmart. On high, they are just a big, oil filled 9 ohm resistor with a great heatsink. 1500 watts no problem.
8 Ohm 100W Non-Inductive Dummy Load Resistor
They will also melt right thru plastic!
The other day I was looking for a dummy load that would take even more power. Found it. My little electric oil filled radiator heaters from Walmart. On high, they are just a big, oil filled 9 ohm resistor with a great heatsink. 1500 watts no problem.
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Ha- I never before considered how they work! Sounds like you can dissipate plenty of power with those! Instead of the oil-filled one, I purchased the ceramic one with the blower fan.
I was also looking that the resistors you linked from PE, but then I just happened to find these at MPJA yesterday.
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