ATV3 volume problem using zone 2

[seejay]

I have my ATV3 going through an Onkyo TX-SR608 receiver which works perfectly fine in all cases except for zone 2. Since zone 2 requires an analog signal I have an optical to RCA jack converter going to the zone 2 on the Onkyo. When I switch over to zone 2 to play anything through it, the volume is extraordinarily low on anything coming from the ATV3. Using the tuner on the receiver to output to zone 2 produces normal sounds levels... at the same setting the ATV3 volume is barely audible even with your ear up to the speaker. To get the volume 'normal' I need to crank the receiver output up almost double.
Does anyone have any ideas here? In all other instances the ATV3 and zone 2 work fine... ATV3 volume is fine in house, and zone 2 not using ATV3 is fine as well.

thanks!