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Old 11th March 2007, 04:03 PM   #1
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Default Inductor help

Do I absolutely need the inductor that goes to my speaker output leads on my amp?
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Old 11th March 2007, 04:05 PM   #2
Salas is offline Salas  Greece
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No if you don't have to face a capacitive load (cables&speaker) in HF and further up.
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Old 11th March 2007, 04:16 PM   #3
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I measured a good wire to be .4 ohms now put 5 of those in parralell then you get a very low ohm reading so would it be safe to say it has nothing to do with restistance only a filter?
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Old 11th March 2007, 04:47 PM   #4
Salas is offline Salas  Greece
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It compromises Damping Factor. If your voltage source has 0.04 it goes against perfectionism to make it 0.4
But if there is any possibility that the amp is going to face some load with negative angle phase (capacitive) then retain the coil. Again to get 0.4 you need 1.5mH 1mm2 air coil, no way a few turns of an output zobel, Explain exactly what and where you are trying to use or modify.
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Old 11th March 2007, 04:55 PM   #5
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Its an audiobahn a18001dt subwoofer amp. I have a thread in car audio im just trying to repair it. I sent an email to audiobahn to see if the will replace the inductor or I can rewind it but cant find wire anywere thats reasonable.
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Old 11th March 2007, 05:50 PM   #6
Salas is offline Salas  Greece
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OK, this is a class D car amp, and its coil is very important, its a crucial filter. Emulate wire gauge, turns and geometry of the original damaged part.
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Old 11th March 2007, 05:59 PM   #7
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What will happen with out it? Can I fix the other problems in the amp first and use jumper wires just to see if the amp works then either repair mine or buy one from audiobahn?
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Old 11th March 2007, 06:15 PM   #8
Salas is offline Salas  Greece
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Only Audiobahn can tell us exactly what will happen. From HF spuriae to dangerous levels of quantization noise or, or....If you must absolutely test it by skipping it, use some spare very cheap loudspeaker driver and see if at least does not kill it and that no bad audible distortion comes out. If all goes well enough, then connect your sub and go step by step with the volume listening for distortion. If it still seems ok...well I would not bet on it for prolonged use. Make a spare or get a spare IMHO.
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Old 11th March 2007, 06:29 PM   #9
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One last question....how or why did this fail? short? to low of an impedance? I bought the amp blown so I have no basis on what happened to it.
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Old 11th March 2007, 07:01 PM   #10
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This is a class D amplifier and the big toroid coils are part of the output filter. They are usually in the 10uH to 100uH range. Never power up the amplifier with any of those coils either removed or jumpered, you are likely to blow the switching stage or other components if you do so.

If the magnet wire is damaged, rewind it with same gauge, turns and geometry (be careful not to damage enamel). If the toroid core is damaged, you are in trouble because there are thousands of completely different types looking almost exactly the same and finding a replacement won't be easy at all.
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