If you ever worry about a bit error happening to your files and not finding out about it, you should use MD5 checksums (or some similar method) to be able to verify that the file has not changed.

The general theory behind a checksum (or “Message Digest” = “MD”) is that it provides a unique 128-bit number for each and every file, based on its content. If one bit changes, the MD5 checksum (sometimes called “hash”) changes. The checksum is repeatable, does not permit discovery of two different files that produce the same checksum, and is non-reversible (i.e. you can’t create the content from the checksum). (more…)

It appears that many old acetate tapes when played on high-quality audio recorders will suffer spoking when left in a play wind condition. I have discussed this problem here. Since posting that, I have taken one of my Racal Store 4DS recorders and removed the heads to save them from wear and now use that to re-spool any tape that shows spoking when played on a Studer A80, Sony APR-5000, or Studer A810. (more…)

The Training for Audiovisual Preservation in Europe (TAPE) Project has just published an excellent Audio Tape Digitisation Workflow document here. It is authored by Juha Henriksson of the Finnish Jazz & Pop Archive and Nadja Wallaszkovits of Phonogrammarchiv, Austrian Academy of Sciences. It is aimed at the newcomer but still addresses all of the major points without being overwhelming. (more…)

Once again, an interesting post on Jill Hurst-Wahl’s Digitization 101 Blog. She started by discussing tape backup issues. In the comments, I discussed my solution of using multiple spinning disks. Another commenter, Ike, provided an extensive review of file system options and his opinions on what works (and doesn’t) for long-term storage. Ike’s comment is fascinating and has lots of food for thought. Here is the post. (more…)

My friend Susan Kitchens blogged about the history of the electret as in electret condenser microphone. It’s an interesting piece of history. I added a little primer to the post on microphone basic types. Look here.

For the last several years, I have been involved with sound reinforcement and recording at my church. I have upgraded the PA system and we’re in the midst of final editing/mastering for an upcoming Christmas CD.

In the process of doing this work, I have learned a few things which might be of assistance. This is the first post in the blog in the live sound and recording category. Many of the posts relating to microphones will also be tagged in the oral history category. (more…)

There has been some discussion recently about the 4-channel cassette recorders that were used for court reporting and other logging- or court-reporter-type applications. It seems that the players only have one output and can select any combination of one or more playback channels into that one output.

This monitoring topology is actually identical to two 1-inch 40-channel reel-to-reel logging machines I have where one can listen to any combination of one through forty tracks on a single output. (more…)

In 2006, I wrote a blog post (here) called “Let Sleeping Tapes Lie: What to do with poorly wound tapes”. For years, tape experts have been suggesting that it is not as good an idea to rewind tapes as was originally thought. This was partially based on the fact that most rewinding in archives was done on the oldest, junkiest machines so as to not wear out the good machines. Unless rewinding is done on high-quality tape transports, it is indeed counter-productive.

We continue to receive poorly wound tapes and are able to play them successfully. So why the quandary now? The reason is that I read portions of another Bharat Bhushan book, Mechanics and Reliability of Flexible Magnetic Media, 2nd Edition, New York, Springer, 2000. Referring to several research papers he makes a compelling case that tapes should be rewound annually if subject to storage environment fluctuations and every 3.5 years if kept in a climate controlled storage area. (more…)

My friend Susan Kitchens and her brother took their parents to the StoryCorps recording session in Los Angeles a few weeks ago. She blogged it here. One of the neat things is that between her article and the discussion she and I had in the comments, we have a good handle on most of the equipment that was used in the trailer. It’s a good selection in my opinion and shows how simply good-quality recording systems can be set up. Further discussions from a StoryCorps representative have shown how clever the setup is.

The question of how to format hard disks (i.e. what file system to use on them) for easy interchange is another FAQ. A recent experience brought home the fact that it is more complex than one might hope. The computer industry is headed towards universal readability, but it is not there yet. The most-able-to-be-read-and-written format appears to be FAT32, although my friend Eric Jacobs makes the point that NTFS is a more robust hard disk file system, and I have to agree. (more…)