Which alignment tape? They are all slightly different. And no one knows what are the typical and the worst case tolerances of azimuth in a typical... and a less than typical... studio. In other words - what is the worst case difference between your machine and the tape made somewhere else, who knows how long ago, that you can realistically expect?
I know full well that on some of those tapes with three tones the 10KHz signal is not exactly a diagonal line... it is an oval.
I usually don't adjust for that, because I am just a casual listener, not a producer. But I would most definitely make an adjustment if I was doing some real work with them.
Hi there,
Thank yo for very good question.
There are numerous sources of alignment tapes available on the market, including MRL. Based on our experience and feedback from customers/studios around the world, there are no trustworthy reliable source that can be used as a reference etalon.
We have tested over 30 pcs of alignment tapes - in past ten years of production we've seen every tape has an azimuth differ substantially (some even up to +/- 60 degrees!), the fux level dropped by 25%, tones level "dancing".
No wonder why some users complaining about a quality of recorded tapes, just because of a "tape producer" trust to whatever alignment tape and had no idea that levels are off, and some users never even bother to align their machines (but that another subject).
There is the International Electrotechnical Commission (IEC) Standard 94, "Magnetic Tape Sound Recording and Reproducing Systems" with parts 2
"CALIBRATION TAPES":
- "tape for making adjustment and comparative assessments of the reproducing performance of both professional and domestic magnetic tape recording/reproducing equipment."
- "Each standard calibration tape shall have at least the following sections: 1) reference [fluxivity], 2) azimuth, and 3) amplitude/frequency response."
For instance for speed 15 ips, requirements for the alignment tape:
- reference flux level (nWb/m), tolerance +/-5%
- signal at reference frequency (1kHz), distortion up to 1%
- level fluctuation up to 10kHz - <0.5dB; over 10kHz < 1dB
- recording angle of 90 deg +/-1` (Azimuth about 0 deg)
We do have developed a process of measure and recording to meet all required by standard (see above) conditions.
An original methodology based on theories of measuring variable magnetic flux level, tone signals level and azimuth.
Utilizing our proprietary measuring instruments, developed based on the methodology at AMPEX, alongside cutting-edge measurement devices (deviation = 0.01% of frequencies and magnetic flux level) we ensure the utmost precision.
To ensure recording and quality control, we employ a special full size heads developed by FluxMagnetics.
All these efforts culminate in achieving maximum accuracy of magnetic flux (including flux level, azimuth, and equalization) recorded onto magnetic tape, fully compliant with the requirements of the international standard IEC 94-2.
Hope it helps.
BTW as an audiophile guy I can really hear a benefit of the correct azimuth alignement - precise calibration would give you a pleasure of better sound stage, details, space.
Next topic we can do about a fringing effect (low frequencies playback ubnormal effect). That would be an interesting subject.
Please contact ATR Service anytime if questions.
Best,
Andrey 
