The reference tapes, at the right speed

Two weeks after the announcer played slow, the tapes for the speed this deck actually runs arrived: the same two jobs as the first pair, cut at 7.5 in/s. Both labels read M2026-08 — made in August, the month the order went in.

The box spine of the 7.5 in/s MRL multifrequency calibration tape: catalog 233-102-450-110, serial 149 515, NAB (IEC2) equalization, 180 nWb/m, tones at 0 and −10 dB, five and a half minutes

MRL Multifrequency Calibration Tape, catalog 233-102-450-110, serial 149 515: 7.5 in/s, NAB equalization — the label adds "(IEC2)", MRL's name for the same 50 µs and 3180 µs curve — 180 nWb/m reference fluxivity, five and a half minutes. This is the tape the manual's reproduce steps want on a machine that runs 7.5 at its high position: azimuth, reproduce EQ, the maximum-level trim and, finally, SRL.

One thing on its label matters more than it looks. The 15 ips tape puts every tone at 0 dB; this one is "at 0 & −10 dB" — the 1 kHz reference at 0 dB, the azimuth and frequency-response tones 10 dB down. That is exactly the convention the maintenance manual's test-tapes section describes for slower-speed tapes, and it means the manual's −10 dB arithmetic, which the calibration article had to argue its way around for the 15 ips tape, applies here as written. A true-RMS meter on the −10 dB tones, not the VU needle, which is only honest to about −6.

The box spine of the 7.5 in/s MRL flutter and speed test tape: catalog 231-570-480-107, serial 149 518, IEC1 equalization, 250 nWb/m, 3150 Hz, four minutes

Flutter and speed test tape, catalog 231-570-480-107, serial 149 518: 7.5 in/s, IEC1 equalization, 250 nWb/m, a single 3150 Hz tone for four minutes. Played at HI it should read 3150 Hz straight, no rescaling: the manual's ±0.2 % window is 3143.7 to 3156.3 Hz. Played at LO it becomes the 3¾ ips check at 1575 Hz. The equalization and fluxivity on this label are beside the point for a speed tone, as the first flutter tape's entry already noted; a single frequency plays no favorites between curves.

The 15 ips pair are not retired. The multifrequency tape still has a use as a cross-check, and the 3150 Hz tape played at HI is the 1575 Hz reading that will confirm, with a number at last, what the announcer's voice said in August.