adat sync question

[cchord59]

So I just got an alesis ai3 ( analog optical interface) To run 8 more channels of audio on my 828. ( the alesis a/d's sound very bland and shallow compared to the black lion upgraded 828).

My questions is, Is it normal to have phase issues when running an adat interface with another interface like and 828 or the like? I find that when I run a stereo signal with one channel going through the 828 and the other through the ai3, I sounds out of phase. But when I run them both through the 828, or ai3 it seems fine.

I'm wondering if they are not totally synced up. I recorded something, and played it back, and it still sounded muddy and dead. Its not totally out of phase, but it sounds just a bit out. But when I look at the waveforms they are totally lined up.

So I guess if the waves are lined up and it still sounds off, then its not a phase issue, and I have no idea whats going on.


any thoughts?
thanks

[Dave Peck]

Why would you patch one half of a stereo signal through one converter and the other half through a different type of converter? You will almost certainly have phase screw-ups due to different amounts of latency between the two converters.

And they waves may LOOK aligned but that's not an accurate way to tell if the phase has been messed up between the two channels. It could be off by only one or two samples and that would be enough to screw up the high end but you could never tell by looking at the waveforms.

All channels that share any signal in common (like eight mics on a drum kit that have some amount of bleed between the channels) should be put through the same converter to keep them in sync. If you need more converter channels for multichannel live tracking, send other signals that do not share any of that signal (like synth DI) through the other converter. It woun't matter if those unrelated channels are off by a few samples relative to the first group of channels.

DP

[Snatchman]

Originally Posted by Dave Peck

Why would you patch one half of a stereo signal through one converter and the other half through a different type of converter? You will almost certainly have phase screw-ups due to different amounts of latency between the two converters.

And they waves may LOOK aligned but that's not an accurate way to tell if the phase has been messed up between the two channels. It could be off by only one or two samples and that would be enough to screw up the high end but you could never tell by looking at the waveforms.

All channels that share any signal in common (like eight mics on a drum kit that have some amount of bleed between the channels) should be put through the same converter to keep them in sync. If you need more converter channels for multichannel live tracking, send other signals that do not share any of that signal (like synth DI) through the other converter. It woun't matter if those unrelated channels are off by a few samples relative to the first group of channels.

DP

Yeah, this is what happens when I send a signal into my Adat based system.. ..I'm using an outboard converter/pre-amp into the first Adat lightpipe. The second/third Adat ( I'm using three), gets signals via analog inputs. ( using their own clock). I hear some weird stuff happening, so I'm going to get the Adat Extenders ( I/O), to hopefully be able to "split" the same clock signal coming from the external master clock to all three Adats at the same time! Hopefully this will tighten things up..!...

[cchord59]

thanks DP.

I would never normally patch a stereo signal through 2 different interfaces, but I was testing the unit to see if It synced up with my 828. I would be using them togather to record drums, were phase shift may be more subtle.

that kind of sucks if thats the way it is though. I will definatly be loosing sound quality if I want to put extra mics on a drum kit. Or mabye I'm being too picky.

[joeq]

Originally Posted by cchord59

thanks DP.

I would never normally patch a stereo signal through 2 different interfaces, but I was testing the unit to see if It synced up with my 828. I would be using them togather to record drums, were phase shift may be more subtle.

that kind of sucks if thats the way it is though. I will definatly be loosing sound quality if I want to put extra mics on a drum kit. Or mabye I'm being too picky.

I would think that the latency that shows up on one half of a stereo pair would be much less than the kind that naturally occurs between mics several feet apart. If your snare mic is in one interface and your floor tom mic in another, the differences in latency of the converters should not be as critical as they would be from the two halves of an X-Y pair.

If you are using more than 8 mics on a drum kit, maybe use the second interface for room mics and front of kit and stuff that is already time-shifted because of distance.

[contempo]

Originally Posted by joeq

I would think that the latency that shows up on one half of a stereo pair would be much less than the kind that naturally occurs between mics several feet apart. If your snare mic is in one interface and your floor tom mic in another, the differences in latency of the converters should not be as critical as they would be from the two halves of an X-Y pair.

If you are using more than 8 mics on a drum kit, maybe use the second interface for room mics and front of kit and stuff that is already time-shifted because of distance.

yup. putting the kik, snare & toms through one interface and the rest of the kit through another is usually ok but splitting the overheads or whatever between two interfaces will case all kinds of audio hell

[uncle duncan]

They should all be clocked by one clock. Otherwise. one clock is fighting with the other one, and it sounds like crap.

[cchord59]

Yeah, they will both be clocked through my black lion modded 828.