Recording Off A Reel-to-reel With A Credit Card Reader

If you’ve got a few reel-to-reel recordings of 1940s radio, how do you transfer those to a digital medium? [Evan Long] and his dad used a credit card reader built for the iPhone to transfer a vintage [Art Kassel] recording from magnetic tape to the digital domain of .MP3s.

A few months ago, we saw what goes into these Square credit card readers. They’re just a magnetic tape head with a resistor an 1/8″ jack that plugs directly into the headphone jack of any iDevice. Because there’s no hardware limitation of what the Square credit card reader can do, [The Long boys] decided to back up some old reel-to-reel tapes with an iPod Touch.

[Evan] and his father needed to perform a few modifications to the credit card reader; the tape head pressed against the plastic case too tightly to allow feeding 70-year-old tape through the device. After bending a bit of metal the credit card reader was ready to record the dulcet tones of the Big Band era.

It’s a neat build, and anything that reuses proprietary hardware (however limited) is alright in our book. Nice job, guys.

22 thoughts on “Recording Off A Reel-to-reel With A Credit Card Reader

  1. Cool idea. Old audio tapes probably have a weaker signal that credit card mag stripes, so a preamplifier may be needed. But if the signal level is adequate, you may still need equalization filtering, and you may need to remove the DNR carrier (modulated ultrasonic frequency used to reduce tape hiss), which can both be done with software filtering. The simple way would be to just adjust the “volume” and “tone” controls in the audio player app, if “pleasant sounding” is more important than “accurate reproduction”.

  2. A question and a comment. Question – if sound is played back through the reader (which seems likely) will it record on the tape? Comment – while its a neat idea if your going to copy more than a few minutes you will need to build a holder.

  3. Can’t quite understand why this was done, unless the head(s) were too worn or the electronics on the old deck weren’t working. Otherwise it’s just a question of feeding the audio output of the old tape deck into the “aux” audio input of your computer and using something like Audacity to record it. Done this on many occasions. I think Robb Wentworth’s comment is slightly off beam. There is a high frequency signal mixed in with the audio to improve (I believe) the response or linearity of the tape, not to reduce tape hiss, but it is fixed and not modulated and I don’t seem to remember head playback pre-amps having to use filters to get rid of it. Way too high to actually be recorded. This may be confused with later Dolby noise reduction techniques.

    1. I was thinking the same thing, the iProduct obviously has a sound input, why not just feed the tape player’s output straight into the phone without the use of a credit card reader. I can guarantee that would give better sound unless the sound circuit of the player is completely broken.

    2. Same here. A good reel to reel has incredibly good sound. Pair that with a nice audio input device on a mac or PC and you will get a much better recording. I believe the sound input on an i-device is limited to 44khz at 16bit.

    3. I did oversimplify, and confuse my terminology a bit. What I meant to say is that old tapes were probably recorded with 40KHz bias, which may be digitized by modern audio input devices, possibly causing aliasing down into the audio range, but at least reducing compression. It would be good to filter that out (if the tape heads even pick it up). Even older tapes may have no bias. Modern tapes typically use 100 KHz bias.

      And the purpose of bias IS tape hiss noise reduction (compensation for large magnetic particle size and low tape speeds).

  4. very interesting hack. for once no arduino. I tried hard to find something to hate about this post but i cannot. Thus I must congratulate you on this build. Good read too.

  5. Evidence of “piracy”,eh? :) Nice hack, but Id try to find a way to affix the reader to the tape deck, this would get old if there are very many hours to digitize. Reminds of similar projects I wanted to undertake, but never will because the recordings are are gone now or their whereabouts unknown now. One, very amateurish “live” recordings of local polka bands at Germans from Russia wedding dances in Kansas. The second, the audio logs from the local Amateur radio repeater, from the time the FCC required the traffic to be recorded.

  6. Go to all that trouble to “preserve” something from the past, then mpee on it. An Iphone is a toy compared to fixing that preamp and doing it right. Azimuth angle is important on the tape head. I still use full 16-44 to record big-band with it’s >than 5kHz top. Our sonic past is in sad hands, witness the damage that bad practices did to a capable medium in such a short time. Digital originally meant flawless serial reproduction. Now it usually means full of flaws and cheats. Always suspect!

    1. Agree. I always transfer vintage stuff at good quality, warts and all, from my 70’s Akai reel-to-reel decks (both still up to spec. and still going strong!) and that gives plenty of leeway for any restoration work that needs to be done. This hack may be OK for a bodge job just to hear the music (assuming that the old deck play-back amp. is not working) but, as has been said, the azimuth (head alignment to you and me!) may not be spot-on and it needs a pre-amp with the correct tape equalization characteristics to get the best from the old material.

    1. Yes, they are amazing :)
      I have two of those myself, and it will stay that way. Despite the fact, that I use computer for recording now.

      And they’re also looking nice! :)

  7. Thanks for the feedback on the project. Just for the record (no pun intended) I didn’t use the iPhone and Square reader to transfer all the tapes to the MP3 format. As I explain on my web site ( I used the traditional method of patching a reel-to-reel to the computer’s input with a ground loop isolator and recorded using SoundForge.

    We did this hack as a proof-of-concept as I am always looking for ways to show how things work by linking the fundamentals to current tools. I’m am a very recently-retired high school technology teacher and the relationship between magnetism and electricity in one of the concepts we covered in class. When I brought a reel-to-reel into my classroom last year and played music on it, students were amazed that the device could record and playback. I realized that we are a generation away from having actually seen analog recording medium and even the floppy disc is a vague recollection.

    So, to illustrate how it all works we looked at credit card readers since they are so common and most students are familiar with swiping them. (In the ed biz we call this “activating prior knowledge.) Since I’d picked up a few Square readers they made a good demo and I was able to show the students that the head in the reader was similar to the head in the reel-to-reel.

    Anyway, my son took it to the next step and developed the iDevice piece which allowed us to bring our two interests together.

    BTW, we, my son and I, have discussed the “piracy” issue numerous times. Yes, these recordings were made off-the-air prior to the Home Recording Act of 1992. In the reel-to-reel community we sort of chuckle at this since any of us with reel machines have likely been engaged in “piracy” and “file sharing” before those terms applied to what we were doing.

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