volume comes and goes on one amp (not clipping)

[swarn2racing]

Folks, I'm stumped. I have a 2000 ford sd that has a JVC HU with 3 pre outs. One pre out goes to a 2 channel sub amp that drives a pair of kicker comp 12s. Second pre out to a 2 channel amp that drives a pair of mtx 6x9s. And finally the 3rd pre outs go to a 4 channel amp that drives 4 mtx 5x7s.

I apologize if ive missed this problem by searching stickys but I couldn't find it so I must ask.

I have had this system in my truck for 2 years with no probs at all. Then a few days ago, I jumped in the truck and all 4 of the 5x7s sound as if I were just sitting there turning the volume up and down at a regular rate. The don't cut off and on, the just fade up and down. up and down on a very consistent cycle. Ignition on...same effect. Ignition off.....same effect. AM, FM, CD, IPOD, Bluetooth, all do exactly the same.

Has anyone experienced this? Just thought I would throw this out to others before I started tearing things apart. This truck is lifted and is a real pain to get the back seat out of it!

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