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.
jminock
Seems strange it does the same thing with two different DACs and the headphones work. The signal is getting to the DAC and the headphone amp works, CD players work the only thing I can think of is some kind of software incapatability sending the signal from iPad to dac  to the preamp. Have you tried connecting a laptop to the DAC USB input ?
At your suggestion I connected a PC via usb to the Benchmark.  Same result, no signal to the preamp.
Did you ever resolve this problem? I also have a Benchmark Media DAC3 and it works great. 

With the Benchmark DAC volume turned all the way down, try turning up the volume on the iPhone/iPad to its maximum after you connect the Apple USB3 camera adaptor to the DAC. Then turn up the volume on the Benchmark DAC.