Mastering digital to Tape (and back)

[fstrat76]

I am in the process of mastering some digital tracks for a band. The tracks are stereo. They have a good
solid mix. My plan was to finish the mastering digitally in Logic Pro, send that output to tape and bring it
back into the DAW.

I went through the process adding any necessary compression and eq. The final stage was limiting and I had a good compromise where the songs were not really slammed to the max. I checked the output wave form and was pleased to see some dynamics. Of course there were some good steady 0db peaks at times throughout the song.

Now, onto tape the limited version goes. The chain is Logic Pro -> Tascam FW1884 convertors -> Tascam M2600 analog mixer -> Tascam 42. The Tascam 42 was bias adjusted again for RMGI SM911 tape.

I set the recorder to average between +1 and +2 VU recording. Recorded the tunes and playback sounded great. It definitely took some of the digital harshness away.

As I recorded the output of the tape back into the DAW, I looked at the wave form and it was noticeably lower in volume. I thought, well this is OK because we just need to bring the level back up to zero, no big deal. I added the gain back digitally, but now it was overloading at key points in the song. In order to tame it, I had to bring the level back down to keep the peaks at 0db. But that lowered the volume of the whole song again, like it was never limited to begin with.

Scratching my head, the only way I was able to correct this issue was to add another limiter on the final file that was recorded from tape, thus taming those peaks yet again. Now, it does sound good but....

Is there something wrong with my signal chain or procedure?

Why are overloaded peaks even being recorded on tape (or played back) when they were limited to begin with?


Still learning.... thanks for any input.

Mike

 

[leddy]

Whenever I record from digital to tape and back, I start with some test tones to set all the levels. I play a 1khz reference tone at the same level as the peak of the digital file and set the tape for the maximum level I'd ever want, since the digital signal will not exceed this (if there is audible tape hiss in the music, I can add some digital limiting to bring up the average volume and get the music above the noise). Using test tones also serves to help you keep your L/R balance from being altered unintentionally. I set the output level to hit digital back in a bit lower to stay far away from clipping. If I need to digitally adjust the final level up towards just under 0db I can. I record it all in one pass, taking the signal from the play head back into digital (that virtually eliminates wow/flutter/hf loss/print through). Doing that, I can't see how you'd ever have a problem.

 

[miroslav]

I checked the output wave form and was pleased to see some dynamics. Of course there were some good steady 0db peaks at times throughout the song.

Are you sure you weren't overloading in the DAW before you went to tape?
Most DAWs will let you go WAY over "0 dBFS" and still not look/sound distorted/clipped becuase they are working with 32-bit float, but once you sum/ouput to analog, that signal is WAY to hot.

 

[fstrat76]

Are you sure you weren't overloading in the DAW before you went to tape?
Most DAWs will let you go WAY over "0 dBFS" and still not look/sound distorted/clipped becuase they are working with 32-bit float, but once you sum/ouput to analog, that signal is WAY to hot.

Well, I know that it was not clipping on the file coming back from tape. A max dbFS search on that file indicates 0bdFS (a kick drum hit at the beginning). I will check the initial file that was prepped before going to tape. Logic would have indicated an overload light over 0dbFS even though there is headroom (6db I think in logic).

But I'm not sure how to explain those peaks and then the rest of the song comes back with much lower volume.

 

[miroslav]

I mix from digital to tape, bringing out 24 channels from the DAW into my analog console, and then it's OTB from there.
The stereo out from the console hits my Otari 5050. While recording to the tape deck, I monitor the Tape, so that "instantly" gives me the PB head output which I then send to my main stereo bus comp and my main stereo bus EQ...from the EQ's output it goes back into the DAW as a stereo digital file.

That is a little different than your setup, since you are taking the finished digital stereo file and then going out to tape...but what I want to say is that it takes a bit of level adjustments between the various gear to find the right balance. Depending on how hard you want to hit the tape and then of course, there is the output level off the tape. I tend to leave the output level at unity, so whatever goes in, comes out...rather than boosting or cutting the output. That way, I can hear how much the tape deck electronics and the tape are getting hit.

Record a stereo file from the DAW right back into it...just to see what you have without the tape in the chain...then adjust as needed, and put the tape back in the path and adjust again.
Also...I would not aim so close for 0dBFS. You can always pull up the level once it's back in the DAW.

 

[fstrat76]

Update:

OK, I looped the mastered version through the M2600 analog mixer right back into the DAW and recorded to another track as suggested. Everything matches nicely. All peaks and averages are where they should be. I slap a peak/rms meter on both the mastered track and the one looped back and the peaks (0dBFS) and averages are near identical.

So it's only to tape and back where the issue is.

I will next try recording back off the repro head while recording and see what that does.

 

[Beck]

Not that this will help you at this point with this particular project, but if you have a decent mix to begin with I would lay that to tape BEFORE doing any fine-tuning with digital editing tools. IMO this is the best place in the chain to introduce analog… if you’re not starting with analog to begin with that is. It’s as close as you can get to starting with an analog mix without actually having an analog tape submitted. So, you basically let tape do its thing before messing so much with it in the digital realm. The differences in levels can be a number of things, but keep in mind tape is not flat of course, so if you’re running so close to 0 dBFS the dips and peaks in the frequency response of tape can be enough to make you have to do some things over. As a general rule the more you dink around with the mix with digital editing the worse its going to get.

Also visit the Pleasurize Music Foundation site and use their guidelines and free plug to see where you’re at with dynamic range. If you crush things too much in the mastering phase, analog isn’t going to help much.

DYNAMIC RANGE | pleasurize music!

 

[fstrat76]

The differences in levels can be a number of things, but keep in mind tape is not flat of course, so if you’re running so close to 0 dBFS the dips and peaks in the frequency response of tape can be enough to make you have to do some things over.

Ah, this may be key. The kick and bass hit in the beginning is where the first 0dBFS occurs, which is fine in digital, but on tape, those lower frequencies may be more prevalent on tape, thus returning a stronger peak as compared to the rest of the song. This makes perfect sense. I will experiment.

I would lay that to tape BEFORE doing any fine-tuning with digital editing tools. IMO this is the best place in the chain to introduce analog

I could still try this because I have the mix files, but the mastering process in this case meant adding linear phase EQ and shaving off a couple db of high end. I did not want to put the mix to tape prior to the EQ tweaks because I wanted the tape to affect the overall sound rather than digital EQ. The current plugs on this particular song are light compressor > Linear Phase EQ > another compressor as needed > limiter. I could take the last compressor and limiter out of the chain before going to tape. Once back in the DAW from tape, I could then place those back as needed.

If I take out the EQ before Tape and place it after tape, then I risk digitally messing with the subtle affects of the tape. Wouldn't that defeat the purpose of using tape to begin with?

 

[miroslav]

Not that this will help you at this point with this particular project, but if you have a decent mix to begin with I would lay that to tape BEFORE doing any fine-tuning with digital editing tools. IMO this is the best place in the chain to introduce analog...

Right...this is what I was talking about earlier for my own SOP. I mix down to tape...but I master all in digital.

 

[fstrat76]

Right...this is what I was talking about earlier for my own SOP. I mix down to tape...but I master all in digital.

I understand where you guys are coming from, and I know the A/D conversion and all that in between contributes, but I have a question regarding that procedure; if you master the song after the tape comes back to the daw, and you have to tweak EQ or compression, aren't you just adding "digital color" again?

 

[miroslav]

Well...you do that anyway if you compress and EQ before going to tape.
I mean...if you do ANY processing in the DAW...you add "digital color".
I don't see that as a problem. Choose the processing that sounds best to you...digital or analog.
It will just have more analog personality if you mix down to tape, rather than just bouncing a finished mix to tape...but even that will add something, as long as you like what it adds.

I also think it's easier to do all the mastering digitally...you have much finer control, unless you have some very $$$$$$ expensive analog mastering tools.