Analog Tape 101—PART TWO,
Recorder Debugging and Alignment


Page 1, 2, 3, 4

 

DOING IT
Put all tracks in Record for a few minutes while monitoring to confirm that Playback/Repro agrees with Input. (PAR applies to narrow-format machines as well as checking Sync on professional machines.) Switch the oscillator to 10 kHz, checking Input first (adjust oscillator output if necessary), then monitor Repro. Severe mechanical problems—dirty, worn or poorly aligned heads, bad tape path—will cause high frequencies to waver.

Internal connector corrosion and dirty relays will cause intermittence, distortion and even channel death. To excite and reveal the aforementioned causes of signalis interruptus, try recording 40 Hz while monitoring repro (if possible), tapping on each channel card. If the monitors are on the meter-bridge, the console may also participate in the cacophony of funk.

If at this point high frequencies are waving or channels are going bye-bye, then call a head-lapping service or a technician, respectively. If a happy machine instills courage, turn it off, demagnetize (it and your tools) and put up the test tape.

TONES
To align Playback, use either an alignment tape (preferred) or a “tone reel” that is known to be good. If you have questions about operating levels (and recommended bias settings), visit the Quantegy Web site—specifically www.quantegy.com/TapeTimeChart-java script.asp#OperatingLevels. Check it out, the Reference Level Table is interactive!

CONDENSED ALIGNMENT PROCEDURE

Here’s the punch list:


1. Playback Level: (1 kHz)
2. Azimuth: 8 kHz and 16 kHz: While adjusting azimuth, note any level discrepancies that may have existed between 8 and 16 kHz.
3. High-Frequency Playback Level: 10 kHz
4. Bias
5. Record Level (1 kHz)
6. HF EQ (level): 10 kHz
7. Bass Sweeps

• On a three-head deck, record bass sweep while monitoring via playback head. Align low-frequency EQ until peaks and dips fall on equal sides of 0VU, then select a low frequency that falls on 0VU. Print that tone on tape and note it on the box. Include the bass sweep if the tape becomes a mix master.

• On a two-head deck, record bass sweep. Check Playback, noting the peaks and dips, then select a low frequency that falls on 0VU. Print that tone (on tape) and note it on the box.

PLAYBACK LEVEL (1 kHz)
Going back to nearly prehistoric times, the earliest “reference level” was 185 nWb/m as shown in the left column of Table 1 below. On professional machines, most engineers choose higher recording levels to take advantage of the increased headroom of high-output tapes, to reduce noise, and/or to increase the “effect” of natural saturation.


Reference levels are in bold type, with “elevated” examples. +1/185 is read as plus 1 dB over 185 nanoWebers per meter. (Visit www.quantegy.com for a more extensive table.)

The level on tape will be referred to as “plus x over y” where plus x refers to the number of dB over the reference level “y.” In modern times, the reference level was raised 3 dB to 250 nWb/m. To avoid confusion, always know and state the reference level; don’t just say “plus six.” Again, Table 1 shows examples of the NanoWeber family (no relation to the outdoor barbeque grill).

Note: On narrow-format machines, level calibration should be according to the manufacturer’s specification.

 

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Reprinted with permission from Magazine, September, 2000
2000, Intertec Publishing, A Primedia Company All Rights Reserved