Tape slowing down during playback

[terribletraffic]

Hi,

I have been recording drums (six channels) to my tascam tsr-8, and have been putting the click track/backing track (guide) on to channel 8 of the tascam, recording it from Logic, thus allowing me the ability to hear the backing track and play along, bypassing all need to use Logic Pro 9.
Then once I've got a good take, I record that on to Logic (all channels have their individual input), and when I come to edit the track, I align the beginning hits with the rest of the backing track (that is now on Logic - as in the one I originally recorded digitally, in order to be able to transfer it to analog and then work with that), and I find that the tape dramatically slows down over the duration of the recording and thus comes out of alignment with the original backing track (but the backing track on the actual tape sounds fine, but it is just a lot quick than the digital backing track.

Why is this happening - is this flutter etc. Or is this a problem with my machine.
I appreciate that this is a bit absurd because of course analog will not be as regimented as digital, that's the whole point and why it is so awesome, but I am fairly new to my machine and using tape, and just want to make sure, there's nothing wrong with my machine!!

Any clues??

 

[The Ghost of FM]

The start up time for the TSR-8 is stated as being 0.8 seconds and the human nervous system has about a 0.4 second reaction delay so those facts taken into consideration ensures that there will almost always be drift when trying to a purely manual lock up exercise to get the reel to play with the computer.

All of that said, if you're finding that the speed drift is off by a second after a minute, I'd suspect the deck is running at spec and the only way to improve on that is employ a synchronizer set up and eat up a track to stripe the tape with time code. If the drift is much more then that, then I might suggest changing the capstan belt and or changing out the pinch roller to ensure there no mechanical issues affecting the speed. The electronics that regulate the speed are regulated by a phase lock looped system which maintains a wow and flutter spec of 0.06%, which pretty respectable.

Another test is to record some rigidly set tones from a keyboard and see if the tuning stays true on playback with the live instrument. If that's staying in, the machine is fine.

Cheers!

 

[mdainsd]

This subject comes up from time to time. There can be a number of reasons. What I hear some of the folks do is to line up the first hits as you say you have already done, then go to the end of the track in the computer and stretch or shrink it to match at the end. I have no familiarity with Logic Pro so I can not state that it has that capability or not.

Others will be along, no doubt....

Welcome!

 

[fstrat76]

I use Beat Mapping in Logic Pro to re-map the click track. Keep the original click track in Logic, record the click track onto Tape, do your tracks to tape, send the tape tracks and the click track back into Logic, and Beat Map the original click track with the click track that came from tape. You'll have to manually map the beat every so often.

I used to do this, but now I use a JL Cooper PPS-1, stripe tape track 8 with SMPTE. I then use my Tascam 38 to sync Logic with the tape.