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Analog Audio

Filed under: — 2006-03-19 by Richard L. Hess — Last Edit 2011-02-04 by Richard L. Hess

At the top level, we are not making a distinction between cassette, cartridge and reel tapes. We will start by creating sub-groups for the different tape widths.

While similar tapes were used for instrumentation and logging purposes, they are addressed on their separate pages and are not discussed here.

There is further discussion of equalization, noise reduction, reels & hubs, speeds, synchronization, tape timing, and tape winding on separate pages.

We, and many other restorers, can transfer audio from tapes ranging in speed from 15/32 to 30 in/s and beyond.

We, and many other restorers, can transfer audio tapes with noise reduction. This requires the physical hardware as no effective noise-reduction plugins have been made. We’re all hoping. We have available Dolby A, B, C, S, and SR; dbx I and dbx II; Telcom C4; and Nakamichi Hi-Com II. That’s nine different types of noise reduction processing!

As of early 2009, we are seeing more and more challenges in playing tapes, and often the challenging tapes are post-1970 and as recent as 2003. We have created a brief overview with a hopefully current list of degrading tapes and links to a more in-depth discussion.

Analog Audio Tape by tape width (in inches):

Recording Standards In addition to track count, it is important to know what standards were used for the recording. Some 1960s recordings were recorded with Ampex Master Equalization which, if not reproduced properly, will sound something like fingernails on a blackboard. This is in addition to the differences between the European and North American standards. This is well-documented at Jay McKnight\’s Magnetic Reference Lab Web site.

Groupings of analog multi-track recording formats

Late 1950s in the U.S. 3-track 1/2″

Early 1960s in Europe: 4-track 1″

Mid 1960s: 4-track 1/2″, 8-track 1″, limited 12-track 1″, 16 track 2″

Early 1970s: 24-track 2″

1970s: 8-track 1/2″, 16-track 1″ (a lower cost, slightly lower quality alternative to the older formats)

1980s: 8-track 1/4″, 16-track 1/2″ (an attempt to lower costs more, with another loss in quality and robustness).

There were a few others, like the 40-track Stephens machines and the 3-inch MCI prototypes, but these never saw widespread use.

Here is an example of head assemblies from various analog magnetic recorders with a brief guide to identifying parts. Click [or save target as] for larger view.

head configs

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