Maybe some of you with more knowledge about a/d converters can help me out here. Is there any amount of delay in the analog to digital process on converters (just the conversion itself... not "latency" as it applies to DAW's)? And if so, would this vary from one Manufacturer's box to another? The reason I ask is this:
I was called in for a session of drum overdubs. The client wanted to track directly to Pro Tools using his 888/24. I thought I'd bring my HEDD as well. I used the HEDD as the clock master and ran the overheads into it(2 TLM 103's x/y centered about 4 feet over the snare --> pair of V72's). The kick was a Soundelux U195 about 1 foot out --> TUBE-TECH MP1A --> 888/24. Snare was 57 --> TUBE-TECH MP1A --> 888/24. No mics on toms.
I usually get a good sound using this same technique, but not this time. Unless I was smoking crack, I thought I worked out the phase issues already. But the kick and snare seemed so "out there" compared to the overheads. Usually, you know where that place is where all of the mics blend together and it sounds like drums. I couldn't get there. So I switched the overheads over to the 888/24 (still using HEDD as clock master) and everything seemed to blend again (although the imaging sucked). Is this me just sucking ass for the day, or am I really hearing something funky here? The weird thing is that I didn't hear any phase problems. Any thoughts?
This kind of delay is one of the many factors to consider when you are calculating any DAW's total latency. It's ok to refer to any step which induces delay between the analog input and the speaker/headphone output as "latency".
There is going to be some delay inherent with adding any separate converter, but we're talking samples here. This would be the equivalent of moving your OH's a few 44,100's (or 48,000's) of a foot, definitely not something that would make or break the "gel" factor. (Check the specs in the HEDD manual, it should tell you the exact latency somewhere in there.)
My suspicion would be focused on the 888's in this case. They may be f'ing up your kick and snare to the point that they are not compatible with the OH's anymore. You said that when the OH's were f'd up to the same degree as the k & s, everything came back into perspective, right?
To fix the situation, I might try putting the k & s into the HEDD instead, since those are (probably) the "featured" tracks in the mix. The OH's should still blend, it will just sound like you used crappy mic's & pre's for them comparative to the k & s mic's & pre's.
Hope that helps. Let us know if how it turns out.