Here is Jon's Article:
I have addressed this question so many times in the past that I am just going to cut from what I have previously written and paste together the following (modified for you). If it doesn’t address your issue let me know.
First of all, I am now presuming that your goal is to add new tracks to Logic Pro (overdub) and have them fall into PERFECT alignment automatically—without nudging, without any effort at all. No problem with Logic Pro 7 or Logic Pro 8. I know the way I have written the steps may sound offensively simple, but every step is critical.
1. Open Logic Preferences and make sure that Record Delay is set to zero samples.
2. Get a log book or graph paper to start log data-- REALLY
3. Open a new Project and label it Misalignment Test
4. Record an audio click or percussion track, i.e. something with some good transients. call it Track 1. (by the way a pasted loop from GarageBand will not work perfectly—that is another discussion.).
5. I presume that with Rosetta 800 and Logic Pro – Logic Pro input 1 to 8 corresponds to 1 to 8 AD on the Rosetta and Logic Pro output 1 to 8 corresponds to 1 to 8 DA on the Rosetta-- if not modify accordingly. Track 1 is output to 1 Logic, to Rosetta DA 1. Rosetta DA 1 is patched directly over to Rosetta AD 2. Depending on your analog setup this should be a breeze with a patch cable.
6. Create a new track and name it Track 2. Select input 2 as its input.
7. Make sure that you are rewinded to zero and hit record.
What you have done here is bounced Track 1 across D/A converters, thru a patch cable, back across A/D converters and printed to Track 2. The sample difference between Track 1 and Track 2 is your magic number for 44.1 hz. This number will be different for every sample rate that you are working at. I also recently discovered that this number is different from Logic Pro 8. This is why you need your log book so that these precious valuable numbers will be available to you.
There are a number of ways you can precisely determine the sample difference between the two tracks. The following method has proven to be the easiest for me. One is the phase null method and the other is to use the Arrange Window under magnification. REMEMBER THAT AT THIS STAGE YOU ARE ONLY MAKING THE DETERMINATION OF THE OFFSET NUMBER, YOU ARE NOT ACTUALLY MAKING THE CORRECTION.
DETERMINING SAMPLE DIFFERECES BETWEEN TWO IDENTICAL TRACKS
(First of all remember that if a track is delayed it will be further to the right in Arrange track window. If this is at all confusing think about the SPL moving from left to right. If something moves toward the right will be delayed and if it is moved toward the left is will happen earlier. Again, this step is only for the purpose of determining the sample offset--NOT A MEASURE TO CORRECT FOR OFFSET.)
1. Get ready to use your ears to monitor Track 1 and Track 2 simultaneously. Make sure you are working with your tracks in mono and DO NOT PAN either track.
2. Track 1 (not Track 2) Insert --- Logic>Helper>Gain click Invert Phase. and Second Insert--- Logic>Delay>Sample Delay. Again, I am talking about Track 1 not Track 2. Keep in mind that the Sample Delay plugin can only delay. In order to determine the difference between the tracks you can't move Track 2 forward so you must likewise delay Track 1 to match Track 2.
3. Now hit play and monitor Track 1 and Track 2 (preferably through a single speaker) keeping the gains at unity if possible. If need be you can create a a cycle or loop if your tracks are short.
4. Start increasing the sample delay of Track 1. You do this by opening the Sample Delay plugin, click the Delay window and scroll up.
5. Simply increase the sample delay until the sound you are hearing is TOTALLY or NEAR TOTALLY CANCELLED OR NULLED.
(FRUSTRATING REASONS WHY YOU MAY NOT HEAR TOTAL CANCELLATION-- If track 1 and track two are coming out of separate speakers you will only get perfect cancellation at one exact spot in the room. If the gains on track 1 or track 2 aren’t perfectly matched you won’t get perfect cancellation. A trick is to listen and change the plugin delay as I described above. When the sound volume drops to its lowest point then tweek the volume of track 1 or track 2 up and down. When you hit the matched volume the cancellation will be optimal. If you introduct color or distortion into track 2 during your original bounce, you will not get perfect cancellation. If fact, the remaining sound that you hear will be the exact sound or color that you introduced.)
6. Write down the SAMPLE DELAY NUMBER number in your log book. This is the magic number= OFFSET FOR that sample rate. Ultimately, you will want to determine this number for the sample rates that you work at.
ENTERING THE MAGIC NUMBER IN LOGIC PREFERENCES
Open Preferences and navigate to Record Delay. Enter your magic number. BE CERTAIN TO PUT A MINUS (-) in front of the number.
Just in case this doesn't make sense to you let me explain. Record Delay under preferences if entered as a plus number will automatically place all new tracks to the right on the timeline. Remember to the right is delayed. Your goal is to have your new tracks automatically nudged to the left or eariler.
VERIFY, VERIFY, VERIFY
Use the same setup that you used to bounce Track 1 to Track 2. Create a new track-- Track 3. Select its input as 2 which is just a bounce from Track 1. Arm Track 3. Rewind to zero. MAKE CERTAIN THAT YOU TURN OFF THE PHASE REVERSAL AND SAMPLE DELAY FROM TRACK 1. Hit Record. Again, you have just bounced track 1 out into the analog world and back. BUT LOGIC KNOWS TO AUTOMATICALLY MOVE THE NEW RECORDING THE MAGIC NUMBER OF SAMPLES YOU ENTERED INTO THE PREFERENCES.
Mute Track 2 and monitor Track 1 and Track 3 simultaneously. Reverse the phase of of either Track 1 or 3 and you should get near total cancelation just as you did when you were determining the sample offset. Try changing sample delay in both Tracks 1 & 3 with the phase inverted on only one of the tracks if you are able to get more phase cancelation then your original number is probably off. Don't sweat a few samples as each sample is only 23 millionths of a second at 44.1KHz sample rate.
I know that this sounds like a big deal if you are just reading this. Once you do it a couple of times it only takes minutes to make the calculations for offset. Tips for making things faster-- save your Gain and Sample Delay inserts settings by clicking and holding over Inserts and select Save Channel Strip Settings. I named it misalignment test.
Now that you have entered the magic number in preferences and have verified that it is correct just leave it as long as you stick with the same sample rate. My tests revealed that I can vary buffer size and the track misalignment doesn't change. And you can increase CPU load and and track misalignment will not vary. I know many unwitting folks on the GearSlutz forum argue this from there arm chairs because they are emphatic about what makes sense to them, not what they have actually tested.
Get out your log and run your system through the paces determining and verifying how the offset will change as you change sample rate but not with buffer or CPU load change.
If you are having trouble doing the phase cancellation test try the following test to make sure you are setup properly--- Start a new project. Record a single track (track 1). Copy track 1 to track 2. Now you have two identical tracks. Add the plugins as described above. When you reverse the phase on track 1 you should get 100% cancellation (no sound). If not something is wrong with your setup.
TIP—Once you determine the magic number for a give sample rate just enter it into Logic Preferences and leave it. You don’t have to turn it on and off. Logic doesn’t care if your first track or tracks are moved a bit because they aren’t being compared to anything. Then any new tracks will automatically, perfectly aligned with previous tracks.
Change of topic
You have a nice setup with your Studer board. If you ever want to use outboard gear as inserts in your Logic tracks during mixdown ITB there is a way to calculate the round trip latency which is critical or phase issues WILL occur. If you use inserts in the analog relm on your board that is not the same issue.
Give your setup a cool way to do mixdowns would be:
Send tracks, groups, or stems to the Studer. Strap in any analog outboard gear you have and want to use. Send your analog stereo mix to a TASCAM DVRA1000. This way you can work in Logic Pro at say 88.2 to optimize the processing of plugins at a higher sample rate. Then you can print your stereo mix to what ever sample rate you wish off of the analog board. If you are making a demo printing directly to 44.1/16 beats the hell out of any sample rate conversion and bit dithering in any DAW platform. The only exception might be conversion done by the Weiss products. The first generation TASCAM DVRA1000 can be had for a song. Warning—the TASCAM converters aren’t great but not bad. Ideally, you buy the best set of converters you can affort to feed the DVRA1000. I use a Cranesong HEDD to convert my analog stereo bus to digital and feed that signal AES cables to the DVRA1000. If you are using an analog board it is so nice to not have to bounce back into the DAW for the final print. If want to send something in for mastering you can do your final print at 88.2 or 192. This is not digital upsampling which somepeople erroneously do and is totally useless if not destructive.
Logic 9.1.3, OSX10.6.5 ,MAC PRO,2 Quad-Core Intel Xeon, 2.26 GHz,16 GB 1066MHZ DDR3, 4 TB HDs, Lynx Aurora 16, Lynx AES16e PCI card.
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