Digitizing 1/4" Magnetic Audio Tape in the iSchool's Digitization Lab

  
  
  
  
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Title:Digitizing 1/4" Magnetic Audio Tape in the iSchool's Digitization Lab
Creator:Madeline Fendley


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This is a tutorial for digitizing quarter inch magnetic tape using the iSchool’s Digitization Lab. The lab has an Otari MX-5050 for use in digitizing tapes.
First thing you’ll do is put the reel of magnetic tape on the left reel on the machine. You will want the tape to fall over the top, leading down on the left side of the reel as pictured 
You will want to use first use a reel of tape without value, a practice reel, when setting up and getting the feel for digitization so that no harm comes to the tape that you are attempting to preserve.
Secure the reel with the stopper to ensure that it does not come out of place during the digitization process.
Now we will begin to thread the tape over the gears and heads. I will pull the leader down and hook it on the opposite side of this hook. You will see a small groove made for the tape to sit in.
From there, bring it around and under the first head, and continue leading the tape under the main tape heads in the center of the console.
Bring it back up and over the two small cylinders on the other side, letting it rest on top of them, and under the larger head.
Lead the tape to the outside of the second hook, letting it fall into the groove, and pull it up toward the right reel.
Pull the tape over the top of of the reel, bring it over the top from the outside. Up from the bottomright and over the top to the left.
From there you hook the tape, hopefully with leader, into one of the round cutouts made to hold the tape. Hold it there while you turn the reel to the left one or two rotations so that the hold keeps and the tape stays in place, able to wind mechanically onto the reel.
When the tape is properly in position, it should look like this.
Next you will want to turn on the machine using the power switch.
You can adjust the speed using this button. This will be important as the speed must match the speed that was used to record the tape.
Almost always, the tapes will be either 3 ¾ inches per second or 7 ½ inches per second. These speeds are reflected on this machine with the Low and High speeds, respectively.
Push the button in for 3 ¾ ips and depress it for 7 ½ ips.
Most reels will by 7 inch reels, so leave the reel size alone unless you come across a unique size.
Now you will work on establishing the chain. On the back of the machine, there should be two cords coming out of channels 1 and 2. These will lead out of the Otari
and go down to the mixer, plugging into Lines 1 and 2. If you later find that you are not getting a strong signal, a pre-amp can be added to the chain to amplify the signal, but you always want to use the cleanest path possible during digitization. Only put as many steps into the chain as necessary.
The Tape Output cords will be plugged into the left and right channels and lead to the digital converter.
Here they will plug into the Line In on the analog to digital converter.
From there, you should be able to put on the headphones plugged into the digital converter and hear what is on the tape if you press play.
Going back to the Otari, here you will see the control panel. You will only ever use play, stop, rewind and fast forward. When you press play, you should be able to see an audio signal coming from the recording on the tape.
The signal will appear here in these windows, the pointers jumping to reflect the strength of the signal.
You should also be able to see the signal on the mixer displayed with green and red lights.
Press play to ensure that you getting a signal and that the Otari is set on the correct speed.
If it is set to the incorrect speed, the recording will either sound very fast or very slow, in which case you will switch to the opposite speed.
Once you have tested the tape to make sure it is at the correct speed and you are getting a signal, you'll want to pull the tape back, rewind it onto the left reel, so that you can start from the beginning of the recording to digitize.
Going over to the computer, open either Audacity Audio Editor, Sound Forge, or any other audio software of your choice. I will use Audacity for this tutorial.
Make sure that the settings are designated for archival quality standards at 96kHz/24bit in a wav file.
Go to Edit → Preferences, then select Quality. Select 96000 Hz as the sample rate and 24 bit as the default sample format. Then click OK.
Hit the record button, then immediately press play on the Otari. You should be able to hear the recording through the headphones, and see the signal on the Otari, on the mixer, and in Audacity.
For the purposes of this tutorial, I am just recording my own voice so that you can see what an audio sample in Audacity and how the signal reads, but your signal will be coming through the digital converter from the magnetic tape on the Otari. 
If you experience problems getting a signal to come into the computer from the Otari, go to Control Panel, choose Hardware and Sound, then Select Sound.
Here, under recording, make sure that the digital-in is our analog to digital converter, which should be the Creative SB-XFi.
You'll make sure that it is selected, and once it is selected, it will receive a signal here, and then press OK.
If you notice the signal maxing out in Audacity by going over the blue lines or hitting the red zone on the mixer, the sound will clip and become unlistenable.
When this happens, slide the input volume down, here by the little microphone, in Audacity. Now Audacity is receiving less of the signal from the Otari.
You should hear the change reflected through the headphones.
Allow the magnetic tape to play all the way through or until the recording has ended if the tape is not all the way used.
When it is finished, first press stop in Audacity to stop the recording, then press stop on the Otari.
In Audacity, go to File, Export. You'll choose Export rather than Save Project As so that you can save as a .wav file rather than an Audacity Project File.
Designate your file name and give it a .wav extension. In the format dropdown menu, choose Other Uncompressed Files. DO NOT CHOOSE THE WAV OPTION IN THE DROPDOWN MENU.
Audacity’s wav selection automatically compresses the file to 16bit, thus undoing the 24bit selection previously made and the digitized recording will not be preservation quality. Choose Other Uncompressed Files, and press Save.
Here you can enter metadata if you would like, or you can press OK if you have your own metadata system in place.
Whether or not you rewind the tape is up to you. Some preservationists believe that it best to leave the tape on the reel tails out to prevent print-through of the magnetic signal which gives the recording an echoey sound.
If you think that you got a good digitized copy and the tape may not be used again for some years, it may be wise to leave it as is, tails out.
If you choose to rewind the tape, thread the tape back through the heads in the opposite direction and thread it onto the left reel.
The tape should look exactly as it did when threading it before digitization, only the reel on the right is full and the left empty.
Always rewind with the tape spooled through the heads or the tension will be off between the reels, and the tape will likely snap during rewind.
Press the rewind button on the control panel. Be warned that it goes VERY fast. Do not attempt to stop it mid-rewind or the tape will shift and you will end up with a bad rewind and need to redo it.
This will also happen if you try to slow it down unless a trained technician attempts to teach you a method to slow the reels during rewind. In my experience it is best to just let it go.
Remove the reel from the Otari, place it carefully back in its box, and begin the next!
Dock windowTable of contents
Setting Up the tape on the Otari MX-5050
Establishing The Chain
Recording the Tape in Audacity
Saving the .wav file in Audacity
Finishing Up