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Latency when importing analog?
Old 14th July 2005
  #1
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Latency when importing analog?

Say I record kick and snare straight to tape, but not the rest of the kit. Then I record them back into PT. Is there a magic number to make them link back up timewise to the rest of the kit that was recorded straight to PT? (I guess the same applies if you run a snare into a ditressor and record it back on an open track.)
Just curious if I skipped that page in the manual I didn't read....
Old 14th July 2005
  #2
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I think you skiped the whole chapter and term on Syncing.
Old 14th July 2005
  #3
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Well, considering there is no physically probable way that both the tape machine and your DAW started recording the tracks at EXACTLY the same time, it's not a latency issue at all - it's just a matter of finding the start positon.
Basically just move them around until they're aligned. Zoom in really tight to your overhead track on a kick and/or snare hit, and move your kick and snare tracks until they're as closely in phase with the overhead waveform as possible.
Even when you record all the tracks on the DAW at once, the snare and kick will be a bit out of phase with the overheads because of the distance of the mics - and this will likely cause some bass cancellation. So you should be able to get an even more time (and frequency) accurate alignment than you normally get, if you get right in there and manually align them by phase.

There's also the issue of inherent converter latency, which varies from converter to converter (no magic number for you, sorry). But considering all the tracks eventually get put through the A/D only once anyway, this shouldn't even be a factor.
Old 14th July 2005
  #4
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First off you will have the delay from the tape path. Can you mult the BD and SD? Then you can record them to the computer and to the tape with the tape repro also going to the computer. Then you can line up the late tracks from the tape with the computer ones. Then throw out the computer tracks. Do you only have a 2-track?

Off topic a bit, one of my 2" machines was rebuilt in Athens. I like that town.
Old 14th July 2005
  #5
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[QUOTE=pigpen]Say I record kick and snare straight to tape, but not the rest of the kit. Then I record them back into PT. .... [/QUOTE

if you are going to record it back to PT after the fact you will have trouble making them stay in sync unless you are locked to smpte wih both position and clock, but if as recomended you run it through the tape while on repro while you are both playing the sound to the tape and recording back at the same time then its just a slide back. the amount will depend on the gap between heads and tape speed, and convertor latencies.

thumbsup
Old 14th July 2005
  #6
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When I record to tape (with PT), I hit record on the tape machine and then in Pro Tools, record the input signal coming from the tape machine (so there's no delay). After the take, just make a new track called "tape" or whatever and then switch your tape machine to repro and record that into the computer. Then you can slide the track into place by lining it up with the first track, which had no delay. Delete the scratch track afterwards, and you've got your kick and snare tracks to tape.
Old 14th July 2005
  #7
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You guys rule...I have not tried this yet. I was bought the machine to mixdown to, but just hhought it might be cool to track a few things to as well.
It is a 2 track, btw....


Now, back to the second half of my thought, what about the Distressor idea. I always have to slide it around as well. Not a problem, I just keep checking phase with the original until it is right, just curious if there was a ballpark samlpe you guys use to start with. Mine is 75 samples.

Thanks as always
daniel
Old 14th July 2005
  #8
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Quote:
Originally Posted by Drumsound
First off you will have the delay from the tape path. Can you mult the BD and SD? Then you can record them to the computer and to the tape with the tape repro also going to the computer. Then you can line up the late tracks from the tape with the computer ones. Then throw out the computer tracks. Do you only have a 2-track?

Off topic a bit, one of my 2" machines was rebuilt in Athens. I like that town.
Doug Weaks huh? Yea, it is a cool town...if you are ever this way, you know you are welcome to drop in the Pigpen!
Thanks
Old 14th July 2005
  #9
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if u allign those tracks you wont get what youve recorded ( sometimes not a bad idea ) . why dont simply send a test tone to your machine and protools , record it the way you described it , transfer the analogue to pt and measure the distance between the pt & analogue track . that way you have your general number and you can shift from now on . alligning tracks can be done later , if necessary at all ?

Old 14th July 2005
  #10
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Quote:
Originally Posted by pigpen
Doug Weaks huh? Yea, it is a cool town...if you are ever this way, you know you are welcome to drop in the Pigpen!
Thanks

Weeks is the man!
Old 15th July 2005
  #11
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Curtis Franklin's Avatar
 

do tapes drift in their playback? ie if something is aligned at the beginning, will it be aligned atthe end?

sorry for the newb question, ive never worked with tape before
Old 15th July 2005
  #12
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Quote:
Originally Posted by pumadrum
do tapes drift in their playback? ie if something is aligned at the beginning, will it be aligned atthe end?

sorry for the newb question, ive never worked with tape before

Well this is exactly what im trying to say, tapes do drift and they will be out of sync unless you play onto the tape and record from the repro head AT THE SAME TIME. not after.
Old 16th July 2005
  #13
Gear Addict
 

Quote:
Originally Posted by adamcal
Well this is exactly what im trying to say, tapes do drift and they will be out of sync unless you play onto the tape and record from the repro head AT THE SAME TIME. not after.
I do not have the figures for how much an analog tape can stretch, or how steady the tape motor speed is. At best, a tape machine rotational speed will be controlled by a very steady clock such as a crystal oscillator based design. Say you have a real great clock stability of 10ppm (that is 10 parts per million stability or 0.00001 drift). Such a drift is no big deal for say a wrist watch because in one year you lose or gain about 5 minutes a year. But the same drift over 3 minutes is 1.8mesc (milliseconds). For a more realistic 25ppm clock stability, a 3 minutes song will drift by 4.5msec! That amounts to a lot of samples. At 44.1KHz, it is almost 200 samples. The acoustic distance of 4.5msec is about 4.5 feet, so one can view the extra track as drifting by 4.5 feet over 3 minutes – not desirable…

As was mentioned, having smpte clocks every where is the way to go. One can NOT eliminate delays by record a new track while listening to the original music. You need the same clock rate for both old and new tracks. There are a few ways to make it happen, but it does require some attention. In the case of analog tape, the time markers are a part of smpte…

Regards
Dan Lavry
www,lavryengineering.com
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