No sound from new stereo

I bought a new pioneer deh-1100mp car deck, it worked fine for about 5-7 days then suddenly i have no sound.
the deck itself has power, keeps perfect time, seems to tune properly to fm stations etc. there is just no sound.

initially i connected the blue/white wire from the deck to the blue wire on the wire harness which i read in the pioneer manual if hooked up to the wrong place can cause malfunction or battery drain.

i have disconnected the blue/white wire from the blue wire and capped both ends but i still have no sound.

i thought this would be a problem with the pioneer deck so i went back to the store and bought a second one ($20 cheaper woo!) then hooked it up (without the blue/white wire) and i have the same issue. deck works fine but no sound at all.

so i returned the second stereo and now i dont know what to do, i dont know cars very well.. any help would be appreciated. thanks.