A Tape Loop Echo You Can Build

Echo and reverb are now electronic audio effects done in a computer or an integrated circuit, but originally they were achieved through mechanical means. Reverb units used springs, and echo units used loops of magnetic tape. As a musician hankering after a mechanical tape echo unit, [Adam Paul] was left with no choice but to build his own. We featured an early prototype, but now he’s back with a finished version that’s intended to be replicated by other musicians.

The unit takes a cassette mechanism from one of the last still-manufactured players available through the usual sources. It splits record and play heads, with the normal cassette replaced with a tape loop made from extra-thick computer tape. A custom PCB replaces most of the electronics, and the auto-reverse system is disabled.

The result is a functional tape echo system, as can be seen in the video below the break. This is ready to build yourself, with everything on a GitHub repository and an extremely comprehensive build guide, so do any of you fancy a go?

Read about the device’s earlier incarnation here.

18 thoughts on “A Tape Loop Echo You Can Build

    1. In normal cassette (and reel-to-reel) tape players, only one spindle turns! The other usually has a slight friction to keep the tape taught. Maybe I’ve only ever seen cheapos, but…

      1. Uhm, no. They may spin at different speeds due to one having a larger amount of tape on it, while the other has a smaller amount (like a large gear and a small gear). When half way through, the spindles spin at just about the same speed. You could think of it like a Continuously Variable Transmission.

        1. daveboltman describes how the spindles are driven. The winding reel motor runs, the unwinding reel motor is generally not driven, and its drag helps keep the tape under tension. How this is implemented on the hardware: expensive tape decks had 3 motors, one for each reel, and one for the capstan. Cheaper decks used one motor and mechanically switched this to drive one reel or the other.

          On a Studer PR99 open-reel tape recorder, when you start playback without a tape in the machine, the unwinding reel spins clockwise: i.e. there’s a drive current on the unwinding reel motor that tensions the tape.

          1. A motor for each reel and one for the capstan? The expensive ones I’ve seen all had a single motor for reel and *two* powered capstans.

            Think about it: a motor per reel only makes sense if you have an autoreversing mechanism.

  1. “extra-thick computer tape” interesting…

    How thick is (extra thick) computer tape? How thin is normal audiotape I know that the 90min and 120min audio tapes are thinner than normal tape (where normal is the regular 60min tapes) in order to fit the reels. But I never experienced computer tapes (the 1980’s computer tapes for storing games and programs) to be thicker and there really is no need for it to be thicker, it isn’t to be played more or less often or faster than regular audio tape. thicker tape will only increase cost without real benefits to the regular user.
    Therefore I do suspect some confusion here.

    Does anyone know a source where this info is confirmed debunked? With real tape specs that is?

    1. Back in the day, music cassettes came most commonly in C60, C90 and C120, with the number being the length in minutes. Computer tapes were C10 and C15. The longer tapes had to be thin to allow all the tape to fit on the spool. Shorter tapes did not have this constraint.

      1. I understand, but I would like to know how thick these types of “short computer tapes” tape actually are. Many people mention that these short tapes could be thicker, but nobody actually mentions how thick they really are. I’m simply not convinced that shorter tape (C10, C15) automatically means thicker and better tape material. Simply because selling regular tape in shorter sizes and claim that they are better, because you don’t need to rewind that much “all the time”, could be a nice scam. What I mean, where are the numbers, indisputable facts.

  2. Back in the last century (haha) it was not uncommon to adapt old reel and cassette machines to produce tape echo. We would mount a tape head on a slider. That controlled the delay. And we added in and out jacks ahead of the preamp and out before the the output xfmr if there was one.
    Primitive I know but it worked. Problem doing that today is it was noisy. But we liked that back then. It fit right in with the hum from the Marshalls!

    1. Our high school rock band had reel tape echo no money for something else. As you said the echo delay is based on sliding playhead and feedback on pot. I liked to play with it :)

  3. https://en.wikipedia.org/wiki/Echoplex
    Echoplexes allowed you to not only move the record/play heads spacing, but also control how much erasing the erase head provided, controlling how much layering happen.

    It is still common to see bands touring with a tape based Echoplex….even though they haven’t been built in decades. The name Echoplex is now owned by Dunlop for a guitar pedal.

    1. The ‘plex was great, if you could afford one. $300 back in the 1970’s was a lot of money. Plus buying the tape cassettes. Which we learned to repair and reuse.
      Who says musicians don’t know sustainability.
      Binson made an Echorec and Roland had the SpaceEcho, which was later digital.
      I had a Fender can-echo. basically a short delay/reverb on a moving drum.
      But again, by today’s standards they all were incredibly noisy. The Roland being somewhat quieter and costing over $400.

  4. If you are using any sort of plug-in to protect your browser, good luck getting the build instructions site to load – it’s a Wix/Parastorage layer-cake NIGHTMARE! Be prepared to whitelist more than a dozen cascading URLs. To start with whitelist anything with a wix.com or parastorage.com ending including pesky iFrames, then slowly but surely more layers will appear. Even then lots of site functionality will still be broken. Or you could just whitelist all the URLs and cross your fingers. Regardless be very patient, the pages take a long time to load. If all you want is to see is the example YouTube video don’t bother digging it out yourself, here’s the URL:

    DIY Tape Echo Effect – Indifferent Engine – Janky Tape Echo [Demo]


  5. They made endless cassettes for phone recorders. It should be possible to mod a normal cassette to the task. No disassembly required to change a tape. They wear out fast the shorter length goes janky from the get go. Janky dropouts may because of not enough tension across the head which is hard to do right with an endless tape path.

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