Equalization—The bulk of the recordings made in the world are NAB (IEC2) equalizations. I say this because the consumer market generally adopted this standard.

Most European professional recordings are recorded with IEC1 equalizations, while the North American recordings were recorded with NAB (IEC2) equalizations. This difference will affect frequency response.

It is interesting to note that early tape recorders did not necessarily have standardized equalizations.

Ampex Master Equalization (AME) and NagraMaster Equalization are two (and there are several more) proprietary standards that have acheived some widespread use. This PDF file shows a passive AME equalizer that I and a few other mastering engineers have built. The best resource on equalization is Jay McKnight’s Web site.

For Teac Extra Efficiency equalization see this Notes Article.