VIBE Slickstereo 4 Feedback Blows Speakers

[Papa Whiskey]

I'm using a Vibe Slickstereo 4 class D amplifier in bridged mode to drive 2 X 8 ohm speakers wired in parallel. I'm using an Agilent function generator to drive the input stage of the amp with about 430 mA rms of an 11 kHz signal. (The particulars of this input selection is application specific, and not really relevant to the problem).

If I turn off the signal generator while the amp is on, horrible horrible screeching comes from the speakers and they basically burn up in a matter of seconds. As long as the input signal is on, everything is fine.

I was originally splitting the sinusoidal input and wiring two input signals into each channel of the bridge. I get good response at a desireable voltage. I thought there could be some kind of input feedback over the Y-connection, but I disconnected one side (halved the voltage seen to the speakers) and the same thing happens.

Is there something I'm missing? Do I need to add some kind of resistor to the input stage to emulate an impedance to prevent feedback?

I'm a mechanical eng. by trade so this is kind of out of my intuition zone.

[ViennaTom]

"I'm using an Agilent function generator to drive the input stage of the amp with about 430 mA rms of an 11 kHz signal."

So this amp has a current input, not a voltage input as usual? odd...