The Importance of Analog Restoration and Digital Conversion
Written by Leon J. Portelance
Introduction: Audio Stored on Tape
If you have recordings you made prior to the digital age or even digital recording that used some kind of magnetic tape to store the data (ADAT, DA88, etc.), there is something you need to know: magnetic tape starts to disintegrate over time. The “glue” that holds the metal particles onto the polymer tape starts to deteriorate and eventually trying to playback these tapes will result in the loss of metal material which not only gums up the tape heads on the machine, but eventually results in loss of quality of the music. When enough time has past, the tapes may become totally unplayable. So if you have anything stored on magnetic tape that you care about or that is important to you, it is critical that you get it transferred to pure digital format as soon as possible.
There are several companies in the US that specialize in magnetic tape restoration. I used the services of Mr. Toad’s in San Francisco and despite their funny name, they did a fantastic job. I had three 2″ x 16 track tapes that were recorded in the late 1970s and about twelve 1/2″ by 8 track tapes recorded in the early 1980s. Between the two batches, I had about 16 songs. They were all from projects that never got finished. So I decided I would release a CD of classic rock and pop from this unfinished material.
Analog Restoration and Digital Conversion: Step One
So step one was the transfer of the material, track by track, into 24 bit, 48 kHz wave format (my preference for working in Logic Pro 9, my DAW for choice). Fortunately my tapes were still in pretty good shape, they only needed to be converted and Mr. Toad’s did not have to do any restoration to the sound. It was still not cheap though, I spent about $1,000 having all of the material transferred and it had to be done in real time. So at 20 minutes per tape at 15 ips, I had about 300 minutes or 5 hours of material plus setup and processing time. Mr. Toad’s delivered my material on DVDs as 16 track or more of individual wave files per song can run 500 to 700 Mb per song. On the 1/2″ tapes, it was more like 40 tracks per song, so over a Gb per song.
Analog Restoration and Digital Conversion: Step Two
Step two: for the six songs that came from the 16 track tapes, it was pretty easy, I just had to import the wave files into Logic Pro and the song were ready to mix. Not so easy for the songs from the 1/2″ tapes though; they had been recorded on two Otari 8 track recorders which were originally sync’d together using time code. I had a master and slave for each song plus at least 3 or 4 work tapes where I had assembled material on (multiple acoustic guitars, real horns and strings, BG vocals, etc.) to bounce down sub-mixes to either the slave or master. So each song was spread over five or six reels. The problem was, in the conversion process, by not having the original tape machines sync’d together, all of my tapes played back at slightly different speeds which meant that not only where they no longer in sync, they were also slightly out of tune with each other. A rather major problem, only the wave files taken from the two master tapes where still in concert tuning.
Analog Restoration and Digital Conversion: Step Three
So step three was to get them back into sync. This was a long laborious process. I imported all of the tracks into Logic and lined them up for each song in groups of 8 with the 8 master tracks on top. I then went in and cut each song into 8 bar segments. I had to do this at a different location for each reel because of the varying tempos. After I cut every song into 8 bar segments, I used Logic’s “Time Stretch Regions to Markers,” function to make every 8 bar segment the same length as the master and then lined them all up again. Everything was now back in sync. At first I had tried applying the Time Stretch function to the whole song, but it didn’t works as things still drifted around, I found that using the 8 bar sections were small enough to give me accurate results.
Analog Restoration and Digital Conversion: Step Four
But now that they were in sync, there was still one more problem, they were not in tune. Step four: I used Celemony’s Melodyne to set the pitch back to concert tuning for all of the tracks except for the ones that came from the master reels and were already in tune. This too was a very long and laborious process as my computer was only powerful enough to let me run 2 or 3 instances of Melodyne at a time. But when it was done, I had all 13 songs setup in Logic, in tune and in sync, ready to mix.
Analog Restoration and Digital Conversion: Step Five
Step five, I mixed all of the songs as best I could and then bounced them all to stem files (individual wave files of each track that when played together at 0 dB exactly sounds like your mix). I sent the stem files to a young mixing engineer with great ears, Isha Erskine (http://ishaerskine.com). He tweaked my mixes to make them sound as good as possible and after a few rounds of comments back and forth, he sent me the final mixes in 24 bit, 48 kHz stereo wave format.
Analog Restoration and Digital Conversion: Step Six
Step six, I sent the mixes to Abbey Road Studios in London (http://www.abbeyroadonlinemastering.com) where they were mastered by Adam Nunn and he returned them to me in the standard 16 bit 44.1 kHz stereo wave format, ready for release. One song did not feel quite finished, so I ended up with 12 tracks for the CD.
Analog Conversion and Digital Restoration: The Results
This project took me two years to complete. Was it worth it? I will let you be the judge. The CD “A Little Bit Crazy,” by my band Vinny’s Last Ride or VLR for short has been sent to iTunes, Amazon and all major online music distributors for release. Physical copies of the CDs should be available at CD Baby and Amazon in a few weeks. You can preview the CD and download it here: Vinny’s Last Ride Preview. You can also watch one of the tunes on YouTube:
So the moral of the story is: if you have an valuable material stored on analog tape, get it converted to digital while you still can! I am glad I did, otherwise the material on this CD would have been lost forever.
To view more articles written by Leon, visit the Audio Mastering Section.