View source for Tape Recording Calibration and Metering

Accurate calibration of a tape based recording is necessary to match record and replay levels, and is critical for [https://en.wikipedia.org/wiki/Dolby_noise-reduction_system Dolby] tracking.

Reference:
* [http://walkman-archive.com/articles/guide-excellent-recordings_05.html Walkman Archive]
* [[Media:Marantz Reference.jpg|Marantz Reference]]
* [[Media:BASF Meters and Measurement.pdf|BASF Reference]]
* [https://en.wikipedia.org/wiki/Compact_Cassette_tape_types_and_formulations Wikipedia - Tape Formulations]

== Recorded Flux ==

* 3% distortion is generally considered maximum acceptable.
* MOL (Maximum Output Level):
** Level that produces 3rd harmonic distortion of 3%
** Frequency dependent. At high frequencies can't be used as harmonics won't be reproduced.
* SOL (Saturated Output Level):
** The level which produces the maximum output. More record level reduces playback output.
* Measurement of flux can be open circuit or closed circuit
** 200 nWb/m closed circuit = 220 nWb/m open circuit (Dolby Level)

== Metering ==

Three standards:

* DIN
** 0 dB is 250 nWb/m 
** Dolby level shown at -1.2 dB
** Used by Marantz, Sony, TEAC
* Nakamichi
** 0 dB is 200 nW/m
** Dolby level shown at 0 dB
* Old Philips
** 0 dB is 160 nWb/m
** Dolby level shown at 2.8 dB
** Most common, used by Aiwa, Akai, Pioneer, Technics, etc

True VU Meters have a tightly controlled professional definition of response, but are more approximate in consumer grade equipment. They show an average signal level over time, and smooth out sharp peaks.

* 3% distortion level is usually around +6 to +8 VU

Peak Meters have fast response, showing peak levels. Better for use on cassette decks with their lower headroom compared to faster tape speeds of Open Reel decks.

* Generally 0 dB on a VU meter is a lower flux level than 0 dB on a peak meter, by about 3 dB.