Magnetic Reference Lab 399-224-512-119 1/2" Short Two-Speed Calibration Tape with Chromatic Sweep (5.5 min., 355 nWb/m)

The "best" test signal to use for calibrating your tape reproducers depends on the measurement equipment that you have, the flexibility of the adjustments on your tape reproducers, and the level of service work being done.

Although there are many fancy read-out systems that might make your calibration work easier and quicker (for instance, an oscilloscope, graphic level recorder, or real-time analyzer; or a system from Sound Technology or Audio Precision), they are all rather expensive, so most studios use the program level meters ("vu meters") on the tape recorders themselves for routine calibrations.

Although a few tape reproducers have several equalization adjustments each for the high- and low-frequency response, most have one high-frequency response adjustment and one low-frequency response adjustment. So if the transport is properly aligned mechanically (tape tension, head contact, and azimuth adjustment), and you set the high-frequency response to 0 dB at 10 kHz, there's not much you can do about the response at 4 kHz or at 20 kHz. The exception is that if the maximum of the response is at around 10 kHz, drooping to say -1 dB at 4 kHz and at 16 kHz, for the best average flatness you would probably set the 10 kHz response not to 0 dB, but to around +0.5 dB.

Finally, although a "sick" reproducer, or one with newly replaced heads, motors, or electronics, might require extensive readjustments, most reproducer calibrations are just a confirmation of performance, or at most a minor readjustment.

For all of these reasons, the traditional MRL "Multifrequency Calibration Tape" may be overkill for your purposes—too many tones, too long to play thru, too much money. For you, Magnetic Reference Lab now offers these Short Calibration Tapes with a 1 kHz tone for calibrating gain, a 10 kHz tone for calibrating phase (azimuth adjustment) and the highfrequency equalizer, optionally a 100 Hz tone for the low-frequency equalizer, and a Chromatic Sweep (described below) for verifying the response over the whole audio range. All are recorded with fringing compensation; with 355-nWb/m reference fluxivity; and 5.5 minute duration at two speeds, 15"/s and 30"/s.

The voice announces the next frequency to be heard, except the last announcement (20 kHz) which follows the end of the sweep.

If you have absolute pitch on A = 440 Hz, you will notice that this scale is about Cth tone sharp, because the reference frequency is 1000 Hz, making A = 447 Hz instead of 440 Hz.

The duration of the tones (670 ms) is sufficient to read the individual levels on a vu meter. More typically, you would probably just note, for instance, that the response drooped 0.5 dB between 4 and 8 kHz, and was -2 dB at 20 kHz.

Specifications:

• Signals and durations, once at each speed for 5.5 min.total duration:
  • 1 kHz, 10 kHz, 100 Hz - 18 s each
  • Chromatic Sweep - 1.8 min.
• Medium: 1/2"
• Catalog Number for Reference Fluxivity of (355 nWb/m): 399-224-512-119
• Chromatic Sweep:
  • Frequency Range: 32 Hz - 20 kHz
  • Voice Announcements: At each octave
  • Steps: Musical semitone (1/12th octave)
  • Reference Frequency: 1000 Hz
  • Duration at Each Frequency: 670 ms
  • Total Duration of Sweep: 110 s (1 min 50 s)