I had to reread this thread, as it's almost a year old.
Philippe...Hi,
I understand your question all the way up to the last line. I am not sure what you mean there. No matter, read on...
If I set my ADAT1 output to BUS1/DIRECT1 on a DM4800, and I then select DIRECT for Channel 1 assignment, I'm supposed to send pre-fader into ADAT1 right?
No.
Just to be clear about your first question, the term "DIRECT" does NOT actually mean DIRECT to an output, pre-module (Pre fader). It means DIRECT to any destination, POST module. When you press the DIRECT button, you first have to associate a module to it, not an input signal. This tells the DM where you are going to send the output of the module...in this case, out Direct (to BUSS CH 1), which will then be POST module. It's a bit misleading, I know.
So, the first thing to realize is that the only way to have a signal effected (via effects and/or volume-pan) is to send it through a module (channel input) and then assign that to any buss or direct output...Stereo buss (most common), Aux Buss, or any of the 16 channel Busses (24 for the 4800), then out from there. Therefore, the only way to send a signal somewhere without going through a module is to assign that signal out of the board via "Input Bypass" (better read as "Module Bypass") The OP was looking for a way to send his signals directly out of the board via ADAT without having them effected by any module. The best way (I could think of) is to utilize "Input Bypass".
On to your issue,
You would like to record your drums with zero latency. So, the question would be, where are you experiencing latency? In your headphones/Monitors? Are you monitoring through the DM or are you listening to the playback of the individual DAW channels as they are being recorded? I ask that because, typically, you should be monitoring your drums using your channel modules going out either your Stereo Buss or ASSN send channels, while the signal itself is being sent off to your DAW unaffected by volume/pan or effects by utilizing "Input Bypass".
My goal is zero latency drum recording, so I want input1 to go to ADAT1 pre-fader, while adding DM4800 post-fader EFX for the drummer's headphone monitors during tracking. I don't like the Input Bypass approach because it precludes me from using my ADAT outs from the bus without de-assigning the Input bypass.
If you want INPUT 1 to go out ADAT1, pre fader (pre-module), then you would need to use "Input Bypass". (Think Module Bypass) as described above from the OP's similar question. That will take care of that.
Next, you want your drummer's headphones to hear a proper mix of himself, and anyone else in the room, complete with the DM's effects mixed in.....There is a great way to do this and it involves the AUX busses and a pair of ASSN sends. Since this is getting a bit long, I'll keep it short. Basically you need assign Aux 5/6 SEND to Effect 1, and AUX 7/8 to Effect 2. Then bring Effect 1 and 2 RTNs back into two paired stereo modules, say channels 27/28 and 29/30 (it really doesn't matter) and run those faders up to unity. Then assign those modules to the same buss (like the stereo buss) that his headphones are assigned to. Now, when you bring up the associated encoder, a parallel version of the module's signal will go out to the effect, and you will hear the return. It works great.