I never could figure out the reasoning for using non-inductive resistors.
As I see it, in actual use, speakers themselves are inductive devices, not purely resistive.
So that would thus be more of an "actual" load.
I'm not sure how practical it would be for such low resistance values, but one solution (no pun intended) that I've seen used for large pulsed power supplies uses a a tube of water and two electrodes, one on each end. Copper sulfate is added to get the resistance to the desired value.
Unlike a wirewound resistor, this won't go open with a 10 kA pulse. Additionally, it can be configured to have extremely low inductance.
I do not see a real reason why an audio amplifier needs to be tested into a non-inductive load.
Unlike a wirewound resistor, this won't go open with a 10 kA pulse. Additionally, it can be configured to have extremely low inductance.
I do not see a real reason why an audio amplifier needs to be tested into a non-inductive load.
EBG power resistors on my experience, are the lowest distortion high power resistors available. The are non inductive bulk metal with a large thermal transfer surface for a heatsink or CPU cooler. I was able to get orders of magnitude lower THD using these vs wirewound rheostat ceramic style ones.
EBG UXP/300 10 Ohm 300W Non-Inductive Bulk Metal Resistor for Amplifier Load | eBay
EBG UXP/300 10 Ohm 300W Non-Inductive Bulk Metal Resistor for Amplifier Load | eBay
Fwiw, I'm testing a lateral MOSFET that has no trouble operating at low impedance, and will most likely be run 4ohm nominal. My hope was to have at least 3ohm, and by that I mean no more than, and no less than 2ohm. This being potentially the worst case during normal usage with a 4ohm speaker. It was a lot of fun playing with some magnets and various frequencies with this thing. I didn't expect the transformer to put out as much as it did, about 1x-1.2x .
Because it adds distortion to an amp being tested. The amp’s performance is usually defined as a non inductive pure resistor.
Well, if we run a square wave test to check the amp's compensation, any (partially) reactive load may mislead the interpretation of what we see on the scope.
Best regards!
I like that the amplifier can support dips into the 2 ohms realm. Amps in general, especially commercial ones, should be stable at least down to 2-3 ohms since normal impedance value for speakers are usually rated 4-8 ohms but will dip lower in many cases.
Keep up the good work synonymous!
Do
Keep up the good work synonymous!
Do
Thanks DO
The idea here is to actually have enough transistor to handle loads all the way down to shorts. It is a rare event to have an amplifier shorted under full load, however, each of the laterals have a continuous drain current of 16amps and dissipation of 250w, I will have four total per-channel. I also find my heatsinking more than adequate to keep them in spec under these conditions. here's a quote from the Exicon page..
"Freedom from secondary breakdown and thermal runaway make them extremely reliable and remove the need for protection circuitry."
In it's current form, I have measured the full output power between 200-250w using an Antek in the prototype rated at 200VA. This setup is acceptable for just a single pair of the double-die laterals, whereas in the future, I intend to potentially double both the VA of the transformer and the intended 4 lateral MOSFETS per-channel. All considered, this should be an optimum configuration, making the most of each capacity. I just don't know of any speaker systems that will be able to handle the power, 350+w@4 and prolly near 250w@8. Somebody must have talked me into this?
S
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