Is my reciever coverting back to digital?

I have a Yamaha dsp-e492, it has no digital inputs, but it does have a sub-out, which sends out 120hz and below from all the inputs, except from the 6 channel discreet inputs. It has dolby pro logic processing available as well. Does this mean that the processor converts all signals into the digital domain, and then back to analog?
I know I shouldn't be using this thing as a stereo pre-amp anyway, but I'm wondering how much I'm really missing out on by not having, say the adcom gfp-750 or a similar ht bypass pre-amp in my system...

yamaha dsp-e492 3-channel surround reciever
adcom gfa-2535 4-channel amp
monitor audio bronze b2 fronts and center (junk surrounds and sub)
philips dvd963sa
I bet, but do not know, that it is converting to digital and then back again...that's how it gets the prologic surround channels from 2 channel. My nice old, old lexicon processor converts to digital and then back. If and when I can afford it, I want a processor with digital in so that it does everything at once in the digital domain and there is no a/d conversion.
If it has no digital inputs, I doubt if it does anything digital. Your sub out is probably the result of analog filters.
Ooops. I assumed the unit was a receiver but it ain't. Just looked at the manual ( and I suspect everything is digitized except the passthrough inputs.
Thanks for the response Kr4. Is there any way to know for sure whether it converts everything even when the effects are off? It doesn't seem to say in the manual either way.
Ok, called Yamaha and they said it's all analog. No digital inputs, no dac's.
I still have a sneaking suspician this thing is a limiting factor in my system.
Pro logic is an Analog circuit. It's not DAC!(digital to analog conversion). The "digital soundfield processing" Yamaha uses(in addition to pro/logic) takes sound and "adds" digital delays and processing to the sound, not converting the whole thing to digital! It's an "additional process", not an entire transformation of analog to digital.
For a full explanation of how pro-logic works, I suggest a search on the net.
hope this helps