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Convert Magnetic Tape Faster Than Real Time?

  1. Jul 25, 2013 #1
    Convert Magnetic Tape Faster Than Real Time???

    I am new to the physics world but considering majoring in physics with an acoustics emphasis, I'm really excited! In my magnetism and electricity class there was a little section on magnetic tape. I found it very interesting though I don't understand it fully. I work for my university library converting Reel to Reels and Cassettes to mp3's so far the best system we have found is simply re-recording them digitally with programs such as protools. It is a very time consuming process because you have to play the recording in real time. Is it 'physically' possible to create a machine to do analog(magnetic tape) conversion to digital format faster than real time while maintaining quality at the same time? Thank you for considering this question, it is my first post and I hope this is an appropriate place for it.

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  3. Jul 25, 2013 #2
    I have my doubts. It's not my area but if you up the tape sped then you may find that the amplifiers do not have the high frequency response to cope.
    A better approach might be to set up several conversion units at the same time. Once each tape is in digital form then any editing can be done without spooling through the tapes.
  4. Jul 25, 2013 #3


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    It would be possible to create a machine to do this, but such a machine would need components designed to operate at higher frequency. Say the audio range for a tape is 20hz to 20khz. If the speed is doubled, then components that operate with a range of 40hz to 40khz are needed. Such a device would also need components to convert the high speed audio into a digital format intended for normal speed playback.
  5. Jul 25, 2013 #4


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    When audio tapes were a "standard" format for selling music (1970-1980) they were manufactured by high speed copying. You could even buy "consumer level" devices that would copy tapes at 2x or 4x normal speed.

    But that is only part of your problem, because those machines copied from tape to tape, without any external audio output. Because the recording sensitivity of mag tape varies strongly with frequency, and also noise reduction techniques (like Dolby) were used, converting to a "correct" audio signal at a higher playback speed would most likely need some custom-designed electronic filter circuits, even if you could find an old high speed copier that still works.

    And unless your tapes have been kept in good condition, a high speed copier would have a higher risk of physically damaging them. So best stick to "real time", IMO.
  6. Jul 25, 2013 #5


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    If your tape will play faster than normal it might be possible to try it out. I think Windows media player will allow you to play mp3 at about half speed.
  7. Jul 25, 2013 #6
    Thanks so much for your replies! Pro tools does a great job of pitch shifting without losing much of the original quality, and I have done that. It is interesting to know as well what range of frequencies would be necessary as well as the physical components that would make such a machine possible.

    My next question is more broad. What exactly is 'signal processing'?
    Is it applicable to this idea? My textbook explains that Audio tapes store information by alternating the direction of B (vector, magnetic field) for portions of thin layer ferromagnetic material, and it is by their arrangements and there passing over the playback coil and amplified through audio equipment that produces the sound you hear. Is it possible to 'signal process' the information stored by the ferromagnetic material without actually amplifying it? For example a manuscript can be translated to a different language without ever having been vocalized. Can you somehow rewrite the information stored on the tape digitally?

    Thank you again! bear with me, it's hard to explain a question you don't fully understand :)

  8. Jul 26, 2013 #7


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    theroundball, Welcome to Physics Forums!

    You are on the “right track” with your idea that signal processing is the technique you would need to detect and store the magnetic tape information at higher speeds. You would then later reproduce that same data in a different format to "write" it onto the new media.

    Here are the two opening sentences from Wikipedia's page entitled "signal processing":

    "Signal processing is an area of systems engineering, electrical engineering and applied mathematics that deals with operations on or analysis of signals, or measurements of time-varying or spatially varying physical quantities. Signals of interest can include sound, electromagnetic radiation, images, and sensor data, for example biological data such as electrocardiograms, control system signals, telecommunication transmission signals, and many others."

    What you are proposing just might result in a new technique. (Think patent) Your new and innovative method would be useful to many who have the same task(s) to perform. This is to encourage you to pursue this, possibly as a class project. You might even get some academic credit. Additionally, you may have your university staff and resources to guide and assist you with the project.
  9. Jul 26, 2013 #8
    Great! Thanks Bobbywhy!

    I will definitely search our research opportunities and faculty support to get a better grasp on these concepts. Wikipedia as always is very enlightening. I am surprised this sort of thing hasn't been developed more. Seems to me that with the digital age taking over it would be important to up the shelf life on all this recorded material!

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