Open reel tapes, head blocks, and unconventional track arrangements at the Stanford Media Preservation Lab
Part of audio preservation work includes working with media that has peculiar characteristics. Sometimes the atypical qualities are a byproduct of how the recording was made by the recordist. An example of this type of problem that we occasionally see at the Stanford Media Preservation Lab is when an open reel tape is recorded over and there is remaining content hidden in certain spots of the tape. This presents specific problems in capture since tape heads are built for use with specific physical configurations of tracks and thus capturing the hidden spots outside of the normal range of track configuration is near impossible. With this in mind SMPL recently worked on obtaining equipment to address this challenging scenario.
To solve this problem we decided to consult the magnetic head and head block expert John French. We at SMPL had heard that in the past John had approached this problem with a special playback head arrangement. So we asked if he was willing to revisit this problem and build a special head and headblock configuration for us and he agreed.
The design included manufacturing a head mount that can be moved on the vertical plane. Then by utilizing a head with narrow tracks (in this case 1/8 track) the playback head could be moved vertically to align the pickup with the narrow band of recording on the tape. John’s design still allows for aligning the playback head for the other standard mechanical alignments such as azimuth in addition to the having a widely adjustable vertical plane.
There are a few drawbacks we are aware of related to this approach, and they primarily relate to how tape heads wear. Tape heads wear in a manner that can force a tape to follow a certain path despite vertical alignment. However based on the numbers of tapes we see with this problem and the different vertical settings we expect to be used we anticipate this problem taking a significant amount of time to occur. If the problem does present itself it can be alleviated through resurfacing (aka relapping) the head in a specific manner.
We are looking forward to using this new tool to discover some of the recorded over audio that we previously couldn’t easily access. There are several photos included that capture the detailed work that went into building this tool.
Above is an image of the front of the headblock
Above is an image of the top of the head block
Above is an image of the back of the headblock