First off, yeah I know I am cheap ... and I appreciate any insight you may have on the issue I am currently experiencing.

I recently installed a Xtrons TD-723 head unit (cheap Chinese double DIN DVD, etc). Everything appeared to be good to go until I installed an amp and sub.

Currently I have the following installed:
Xtrons TD-723 HU (single sub RCA out)
Kicker DS60 - front speakers (driven by HU)
Sony XM-GTX1821 - amp driving sub
Sony Xplod XS-GTX121LW - sub

The issue is that my sub pulsates/deflects to the point of damage. Perhaps at a rate of 2 times per second???

If I disconnect the RCA inputs to the amp the sub does NOT pulse.
If I connect a MP3 player to the amp the Sub does NOT pulsate.

It appears that the sub pulsates no matter if the amp is run normal or bridged when connected to the HU.

I do not know what to do so...
I tried grounding the RCA cable output to the HU body, but it had no affect - still sub pulse.
Checked and double checked and created a good chassis ground for the amp.

Any ideas????