Tape sync questions

[EmilFrid]

So I've been using the DAW Reaper slaved to my Teac 85-16 by using SMPTE, with varying results. Most of the time it works suprisingly good but every once in a while Reaper gets noticeably jittery for a second or so. Having a tape machine as the master is for obvious reasons not ideal, and I'm thinking of building something that will translate the computer's 1's and 0's into capstan language. Most likely keeping SMPTE on tape to provide the computer with a song point position (to start at the right spot) and to control the stop/play interface of the computer, as I feel like it would be impossible to have Reaper tell the tape machine when and where to start/stop and so on and so on. All i want is the computer to act as a stable clock during playback, so that the tape machine can follow Reaper.

My machine actually has a sync interface, but it's only designed to sync two capstan motors with each other. I know lying is a sin, but I feel like it should be possible to fool the capstan motor into believing that it is connected to another motor when in reality it is hooked up to the matrix.

This is foreign terrain to me, so i was wondering if someone more educated has any ideas. Adding schemo below.

Thanks

 

[Tubetec]

Theres all kinds of mechanical reasons your tape machine might not put out a stable time code .
Also dont forget you need a pre -roll of a couple of seconds after pressing play for things to stabilise and sync properly.

 

[EmilFrid]

Yes, that is true, although Reaper is locking incredibly fast. But now that i think about it, I realize I might be trying to do something which is completely impossible. Maybe the only way to sync with DAW as master is by sending timecode to my machine, and building a SMPTE-to-tape-transport box is probably not a DIY thing. Oh well, let's see if someone smarter than I has any ideas... I'm very confused.

 

[Tubetec]

While using the edge track ,either 1 or 16 for timecode minimises any chances of bleed into adjacent audio tracks , it can be problematic , tape width has been known to vary .
Tape path wear might also be an issue , if you see any vertical fluctuations of the tape as it passes the heads that can cause a problem .
You can try printing a 10khz tone to tracks 1 and 16 ,at a reduced level , then check the stability .
You can also be dealing with a tape thats stretched at the edges .

 

[EmilFrid]

While using the edge track ,either 1 or 16 for timecode minimises any chances of bleed into adjacent audio tracks , it can be problematic , tape width has been known to vary .
Tape path wear might also be an issue , if you see any vertical fluctuations of the tape as it passes the heads that can cause a problem .
You can try printing a 10khz tone to tracks 1 and 16 ,at a reduced level , then check the stability .
You can also be dealing with a tape thats stretched at the edges .

I've used track 16 and it works well. My machine is regularly calibrated mechanically (if needed) and electronically, and handles tape well. Also the sync head is new. So I'm not worried about the recorders stability. But the problem with having DAW as slave is that no tape recorder has got perfect timing, and the small fluctuations in speed can lead to instability in the computer. Thats why I'd want the computer as master.

 

[abbey road d enfer]

Slaving a tape machine is not a minor task.
There's a variety of types of motors, which require different control signal. Some need DC, some need pulses, others may need something else.
The Tascam uses pulses. The synchronizing software generates the pulses in a way that makes the tape chase the digital reference. It's this software that's the stumbling block.
Synchronizers used to be a big thing in the 80's and thousands of hours in R&D have been spent on it. Re-inventing the wheel for a one-shot seems hard to justify.
I would say your best bet is to see if there ever was a synchronizer dedicated to the 85-16, either by Tascam or one of the usual suspects at the time, Adams-Smith, Lynx, BTR, Audio Kinetics.
Now, since you have a DAW, why do you use the 85-16?
If the reason is sonic signature, what most people do today is transfer their analog recordings to the DAW.

 

[EmilFrid]

Slaving a tape machine is not a minor task.
There's a variety of types of motors, which require different control signal. Some need DC, some need pulses, others may need something else.
The Tascam uses pulses. The synchronizing software generates the pulses in a way that makes the tape chase the digital reference. It's this software that's the stumbling block.
Synchronizers used to be a big thing in the 80's and thousands of hours in R&D have been spent on it. Re-inventing the wheel for a one-shot seems hard to justify.
I would say your best bet is to see if there ever was a synchronizer dedicated to the 85-16, either by Tascam or one of the usual suspects at the time, Adams-Smith, Lynx, BTR, Audio Kinetics.
Now, since you have a DAW, why do you use the 85-16?
If the reason is sonic signature, what most people do today is transfer their analog recordings to the DAW.

Thanks for the input. Maybe I should search for something like that.

As for the question "why": I hate sitting by the computer, so I only record to and mix from tape. It's actually an analog studio open to the public, and it seems like many bands don't have a problem with the format. Many of them even think it's very cool. Also I like having the end result relatively safely stored in an archive, with the ability to bring the session back within a minute whenever needed.

With the DAW thing I only want it synced because sometimes a software synth sequencer or software drum machine is needed, and I want it to stay in sync with the stuff recorded to tape. And if a client brings a couple of their own audio tracks sync is nice, as they might later realize they wanted to add another track from their DAW which is not yet printed. Stuff like that happens and it is really nice to be able. Other than that, I'm totally allergic to working with screens and nothing has ever changed my mind about that. I only feel sadness and boredom whenever I touch a mouse in a work setting.

Edit: We also have a Teac 90-16 which is a rare and wonderful piece of equipment. It's so well-preserved you'd think it left the factory yesterday. Only one previous owner. I have to admit tape machines are my number one special interest...

 

[RoadrunnerOZ]

If you have DBX or Dolby noise reduction in place this could cause the SMPTE to be out of whack on playback off the sync head. If transiting from rewind direct to play there may be jitter in tape speed causing sync issues - best to rewind (or fast forward), stop, then play.

 

[EmilFrid]

If you have DBX or Dolby noise reduction in place this could cause the SMPTE to be out of whack on playback off the sync head. If transiting from rewind direct to play there may be jitter in tape speed causing sync issues - best to rewind (or fast forward), stop, then play.

On my machine it's possible to turn off the dbx on individual channels so I always do that for the smpte track.

You're correct about the rewind thing, but i am super inpressed by how fast Reaper locks. It's like black magic to me.

 

[abbey road d enfer]

Thanks for the input. Maybe I should search for something like that.

I'm sure there's hundreds of synchronisers sitting in cupboards gathering dust; maybe send a message in a bottle...

As for the question "why": I hate sitting by the computer, so I only record to and mix from tape. It's actually an analog studio open to the public, and it seems like many bands don't have a problem with the format. Many of them even think it's very cool. Also I like having the end result relatively safely stored in an archive, with the ability to bring the session back within a minute whenever needed.

With the DAW thing I only want it synced because sometimes a software synth sequencer or software drum machine is needed, and I want it to stay in sync with the stuff recorded to tape. And if a client brings a couple of their own audio tracks sync is nice, as they might later realize they wanted to add another track from their DAW which is not yet printed. Stuff like that happens and it is really nice to be able. Other than that, I'm totally allergic to working with screens and nothing has ever changed my mind about that. I only feel sadness and boredom whenever I touch a mouse in a work setting.

I understand all this.
I've been in love with magnetic recording for ages, but I happily made the transition to DAW.

Edit: We also have a Teac 90-16 which is a rare and wonderful piece of equipment. It's so well-preserved you'd think it left the factory yesterday. Only one previous owner. I have to admit tape machines are my number one special interest...

I had a 90-16 in the 80's. Very Ampex-like.

 

[RoadrunnerOZ]

Do you record anything onto track 15 - crosstalk bleed from adjacent tracks can cause misread of signal - high attack signals at high level

 

[EmilFrid]

I'm sure there's hundreds of synchronisers sitting in cupboards gathering dust; maybe send a message in a bottle...

I understand all this.
I've been in love with magnetic recording for ages, but I happily made the transition to DAW.

I had a 90-16 in the 80's. Very Ampex-like.

yes, i will listen to your advice and look for a synchronizer which might be able to connect with my machine. Maybe that's my best bet. Would have been much easier if the machine had a built in microprocessor that could read SMPTE, like those from my (perhaps not universally true) experience very unreliable half inch 16 track fostex's.

Oh, you had a 90-16? Cool! Agreeing about the Ampex likeness. The round buttons and all. Also bears some visual similarity with the MCI machines. The electronics is also quite silent – lower noise floor than my 85-16.

Off topic, but I'm posting a pic of my buddies:

 

[EmilFrid]

Do you record anything onto track 15 - crosstalk bleed from adjacent tracks can cause misread of signal - high attack signals at high level

This far I noticed no problems since if you record with dbx you don't record nearly as hot. But what you say still holds true, so I try to keep track 15 clean for as long as possible. If all sequencers and drum machines or whatever are done and we're ready to commit, I'll usually use both track 15 and 16, as we won't need the code anymore.

 

[RoadrunnerOZ]

Have a look at the takeup reel on play start - see if there’s a slight jump or judder - had a problem like this with a Studer that hadn’t had the tensions properly set for a larger reel caused second machine to lag in synching up.
Also what SMPTE code are you using? 24, 25, 30 or 30 dropframe?

 

[EmilFrid]

Have a look at the takeup reel on play start - see if there’s a slight jump or judder - had a problem like this with a Studer that hadn’t had the tensions properly set for a larger reel caused second machine to lag in synching up.
Also what SMPTE code are you using? 24, 25, 30 or 30 dropframe?

Thanks, tension was recently calibrated but its a good idea to check for any problems. Settings can drift pretty fast...

I've been trying out different SMPTE codes. I feel like there's no noticeable difference between 24 and 30. I've seen 30 drop frame but i don't understand what that is.

 

[JohnRoberts]

Thanks, tension was recently calibrated but its a good idea to check for any problems. Settings can drift pretty fast...

I've been trying out different SMPTE codes. I feel like there's no noticeable difference between 24 and 30. I've seen 30 drop frame but i don't understand what that is.

It's been years since I messed with this but IIRC the actual frame rate for video is 29.97fps. So my speculation is that drop frame drops an occasional frame to balance out (something like 4 seconds per hour).
===
29.97fps This frame rate is a holdout from the introduction of color television. The original frame rate of black and white NTSC television was exactly 30fps, but when they introduced color, the engineers had to lower the frame rate just a tiny bit in order to integrate the color data into the TV without screwing up the whole signal.
===
For short projects I wouldn't worry about it, for long recordings it could matter.

JR

 

[nielsk]

Asking digital to chase analog will always result in problems.
There is only one way to reliably do this, as previously noted, use a synchronizer to slave the analog machine to the digital.
You should also run your analog machine resolved at all times (other than when initially striping SMPTE, which should be the first thing you do to a reel of tape after airing it out).

 

[RoadrunnerOZ]

24 fps Film (F)
This frame count is the traditional count for film. It is also used for HD video formats and commonly referred to as “24 p”. However, with HD video, the actual frame rate or speed of the video sync reference is slower, 23.976 frames per second, so timecode does not reflect the actual realtime on the clock for 24p HD video.

25 fps PAL (P)
This is the broadcast video standard frame count for European (and other PAL countries) television broadcast.

30 fps non-drop SMPTE (N)
This is the frame count of NTSC broadcast video. However, the actual frame rate or speed of the video format runs at 29.97 fps. This timecode clock does not run in realtime. It is slightly slower by 0.1 %.

30  fps drop-frame SMPTE (D)
The 30 fps drop-frame count is an adaptation that allows a timecode display running at 29.97 fps to actually show the clock-on-the-wall-time of the timeline by “dropping” or skipping specific frame numbers in order to “catch the clock up” to realtime.

In simple terms the easiest way to avoid confusion and clock disparities is to use 25fps.

There should be no issue whether you slave tape to digital or digital to tape. But - the problem with slaving tape to digital is the sync-up takes longer as the tape sourced SMPTE has to be read off tape, analysed and mated to the incoming SMPTE signal from the digital source - this is done by the synchroniser which then issues servo corrections to put the tape in the right place. If the tape is in a completely different location to the DAW it has to fast forward or rewind and then chase to lock.
Digital slaving is way quicker as the tape derived SMPTE code is read by the digital slave and within a couple of frames it’s locked - no matter where the tape is, as the digital slave jumps instantly to the new SMPTE code location - it doesn’t have to wind tape.
I used this system for years without hiccups with two synched Studers, a Sony digital recorder and MIDI and audio on computer - sync source tape machine 1, track 24.

Initially, black and white video ran at 30 fps. When color video was introduced, the frame rate slowed to 29.97 fps to allow color television to run on black-and-white receivers.
Because originally television was only live and not recorded, the only way to ensure sync between studio cameras and home TV sets was to sync the signal to electrical mains. Mains were 60Hz (30fps) in the US and 50Hz (25fps) in Europe. But television was originally in black and white, so when color came along, SMPTE engineers wanted to keep the color signal backward compatible with black and white TVs. The color video signal had a tiny additional color burst signal between the existing black and white signals and so they slightly altered the frame rate from 30fps to 30/1.001 = 29.970 fps to avoid artifacts, thereby creating the NTSC color standard.

 

[Walrus]

NTSC = Never Twice the Same Colour!

 

[RoadrunnerOZ]

Yeah - we used to call it that when I did my apprenticeship with Philips, color TV was just coming in for the 1972 Olympics - PAL was way superior with a higher line count than NTSC which also looked washed out compared to the PAL color.