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Discussion Starter #1
I've never experienced this, but this is my first Class-D, so I don't know what's going on.

It's a Rockford Fosgate R300-12 300w Class-D 12-Volt Powered Subwoofer + PYRAMID PSV-300 30a Power Supply.

When I feed the R300 clean signal, it's all jarbled and almost sounds like a subsonic feedback loop or something. It's not reproducing the signals at all, but does turn up LOUD via the knobs on the front. All the knobs work, and it gets louder and quieter, the X-over threshold knob works well too, but only affects this jarbled noise.

As soon as I pull the connections and put them back in my other amp, it all sounds very clean - so it shouldn't be the cables.

Is my Class D amplifier "Blown" (it and the driver still pushes a lot of air - it's like the Pre-Amp section is blown)?

I really don't think it's my power supply, it's pumping steady voltage and amps.

This rig has worked perfectly for a long time in my home, but it's been unhooked for a few months, and when I hooked it back up the same way now, this is happening.
 

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Discussion Starter #3
It's not broken, but something weird is going on.

Thanks. I tried option B, and it worked perfectly, so I'm bewildered.

I put the power supply on a separate circuit and plugged my iPod directly into the powered sub. It worked perfectly, so thankfully my Class D amplified sub is not broken at all.

Then I plugged my computer's audio into it, and it freaked out as described previously. As soon as I put the computer's audio back into my receiver, totally clean signal.

The only thing I can think of is some insane ground loop situation, that not only has 60Hz hum, but is somehow feeding back on itself. It's so weird. I used it this way before, but there must have been some variable I'm overlooking.
 

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What is the source?
 

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Discussion Starter #5
What is the source?
The source I'm having issues with is Mac MINI computer's 1/8-inch analog output > to stereo RCA plugs. I've tried different cables, with no result.

The Mac MINI is perfectly clean to my AC-powered receiver, but develops an insane 60 Hz feedback ground loop thing when plugged into DC-powered subwoofer + AC/DC power supply.

I really think it's a ground-loop issue. Works perfectly with battery powered iPod NANO as the source.
 

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Hmmm, ground, LACK of ground... When connected to the AC-powered receiver, what happens when you touch the outer enclosure of the AVR? How about with the sub with AC/DC power? (Be careful about shocks/hazards, of course.) Have you tried adding a ground?
 

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Discussion Starter #7
My HT receiver's power cable has two prongs. It has a ground "screw" for a record player, but I don't know how to add a ground. That's probably my problem, exactly as you say though. Thanks for the advice. I just have to figure out how (and if it's wise) to ground my two-prong plugged receiver?
 

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The only way that you should get a problem with units with no ground prong on the ac is if there is something in the system that has a ground, or if things are plugged in to different circuits and one of them has the neutral and hot reversed. Or you have a unit that is defective.
 
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