Mahakala Thangka, courtesy Marian Bond
Image courtesy of Andy Fenton
Image courtesy of Feilding Public Library http://feilding.recollect.co.nz/nodes/view/16671
Home » Services » Audiovisual Digital Capture » 1/4" Reel to Reel Tape Digitisation

1/4” Reel to Reel Tape Digitisation

Reel to Reel audio tapes used to be the main way to capture sound and a number of recordings were produced on these before the advent of much less complicated cassette and 8 track tapes. They were most often used in broadcasting and music industries for recording radio shows and bands, and a large number of both amateur and commercial recordings were produced on 1/4" tape.

Why should I digitise my tape based recordings?

You may have old reels tucked away and they will likely be starting to suffer now. Many of the older magnetic tapes now suffer from "sticky shed" syndrome, which makes it important to have them stabilised and/or converted to digital to ensure they last a much longer period of time. Sticky-shed syndrome is a condition created by the deterioration of the binders in a magnetic tape, which hold the iron oxide magnetisable coating to its plastic carrier. This deterioration renders the tape unusable. Some kinds of binder are known to break down over time, due to the absorption of moisture from the air (hydrolysation).

The symptoms of this breakdown are immediately obvious even when rewinding the tape: tearing sounds and sluggish behaviour. If a tape with sticky-shed syndrome is played, the reels will make screeching or squeaking sounds, and the tape will leave dusty, rusty particles on the guides and heads. We commonly bake tapes to temporarily repair sticky-shed syndrome to allow the tapes to be digitised.

Depending on tape speed, we capture from either our Studer/Revox B77 MKII, or Otari 5050MX-II reel to reel tape player.  We  digitise 1/4" mono and stereo tape with the following speeds:

inches/sec cm/sec Normal use
15 38.10 Most common speed professional studio recording
7 1/2 19.05 Most common pre-recorded playback speed, highest domestic speed
3 3/4 9.53 Second most common pre-recorded playback speed
1 7/8 4.76 Lowest common reel to reel speed

 

"Baking" tapes? What's that and why do you do it?

The binder is the weak point of most audio and videotapes. In the late sixties, polyester urethane became a popular binder for tapes because of its low cost and durability.

The binder is the chemical compound that holds the oxide particles together and sticks them to the tape backing. Under humid conditions (which means anything but controlled low-humidity storage), the polyurethane used in the binder has a tendency to absorb water. The water reacts with the urethane molecules, causing them to migrate to the surface of the tape where they gum up the tape path during playback.

Short strings of urethane molecules are particulary prone to water absorption, while long strings make the coating mixture too viscous to produce good tape. Middle-length strings are the best, but the tape manufacturers didn't know this at the time, and didn't always know what they were getting. In the case of Ampex tape, tapes most likely at risk are 406 and 456 manufactured from approximately 1975 through 1984. During those years, Ampex tested the goop they got from their binder suppliers simply by measuring viscosity. Unfortunately, the long and short strings average out, viscosity-wise, to a viscosity about the same as the ideal medium strings, so some tape was inevitibely manufactured with an overly great proportion of short urethane strings in the binder. In the worst cases, as little as 3 days' exposure to 70% relative humidity can cause a tape to become gummy, but typically, it takes 2 to 15 years under normal, people-friendly ambient conditions. In 1984, Ampex started doing it's incoming inspection with a high pressure gas chromatograph (that's when it was invented), and was able to more accurately determine the molecular makeup of it's binder, and control production much more carefully.

The first sign of binder breakdown is usually the presence of a powder or a gummy residue on the surface of the tape. When the tape is played, this residue attaches to the playback heads, with results ranging from poor (or no) playback to a jammed machine, and/or damage to the playback heads. The tape can be made playable by using a tape-cleaning machine to remove the powder from its surface or by "baking" the tape.

The good news is that the "sticky shed syndrome" resulting from water absorption by the short urethane molecule chains is almost always fixable. The process for repair is commonly know as "baking a tape". The fix lasts about a month under normal storage conditions, and Ampex claims that a tape can be re-baked any number of times without ill effects.

To bake a tape, you want to expose it to even heat, ideally at 130 degrees F (54°C - we use 58°C), with a variation of less than plus or minus 10 degrees. Too cool and the process is ineffective, too hot and you're starting to risk increasing print-through (this means that some of the particles transfer from one piece of tape to another, with a resulting "ghost" image of sound or video on the tape affected).

We've achieved our best results using food grade dehumidifiers, and we test using hygrometers to ensure that the air in the dehumidifier reaches around 25% to 30%RH. This is a process that can take between 5 and 72 hours, depending on the degree of hydrolisation.

 

What we do:

  • We inspect the reel tape.
  • If necessary we will bake the tape to ensure that it can be used safely.
  • Tapes are digitised to 24 bit/96kHz quality, and individual tracks can be split out for easy navigation.
  • Audio files can be written to .WAV files at 24 bit/96Khz quality, or written to CD at 16 bit/44.1Khz.

PLEASE NOTE:

  • Quality can vary due to the condition of the original tape recording.
  • If you have a large number of Audio Reels, we can look at a bulk order discount for you.
  • Subject to copyright- We will not copy, copyright material. Section 81A of the Copyright Act 1994 does allow you to make a backup copy of an original recording that you own, for personal private use only.

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