Sherwood RD-6405

Hi Guys & Gals,

I have recently acquired a Sherwood RD-6405 receiver from and i have hooked it up but can get no sound from the digital inputs.

When I select the optical (toslink) input, or either of the coaxial inputs it flashes the input on the display indicating that there is no sound being input.

I am inputing from a macbook's optical out and my dvd players coaxial out.

Any ideas?