How do I connect my playbook to my bench......

Wise Ones,

I am trying to connect my Playbook to my benchmark headphone amplifier /DAC. My main purpose is just to get sound from the headphone amplifier, pretty much bypassing the dac portion for the moment, trying to move one step at a time.

My playbook is currently standing on my BB docking device which I love. Once the Playbook is on this docking device, I only have access to the headset jack of the playbook, a (3.5mm)input on the very top right hand corner of the playbook.

I tried a 1/8 jack to RCA Audio adapter and there is no sound from the amplifier. (I have tried this with my other PS Audio headphone amp and I am getting sound from that amplifier).
I also decided to try a Toslink To Optical Mini Adapter and plugging this directly to the DAC portion using an optical cable and same results, no sound.

Am I missing something here?
Truly appreciate any feedback.

Thanks