streaming with benchmark2-dx DAC - problem - no signal to preamp

I am trying to stream from a newly purchased Benchmark2dx DAC via usb, using the benchmark usb cable connected to an Apple USB3 camera adapter, which is connected to a new ipad.  The camera adapter is also connected to a wall charger.  There is signal to the DAC's headphone outputs, but no signal to the Anthem preamp. 

The DAC is connected to the preamp's dvd intput. The disc player plays fine on that intput through the DAC. 

I called Benchmark tech support.  They were helpful, but we could not identify the problem.  I expect I am missing a basic setting, any help appreciated.