What is Azimuth, and what does an out-of Azimuth recording sound like?

Azimuth refers to the angular relationship between the recording tape and the record head (and play head) head gaps. Adjustments are particularly critical, especially in the case of short wavelength (high frequency) signals. The head gap must be exactly perpendicular to the direction of the tape travel; that is, the tape travels across the head gap at a 90 degree angle.

If the angle is not 90 degrees, you will hear varying qualities of muddy sound, as the maximum amount of high frequency energy recorded on the tape cannot be picked up up by the tape head. Generally, tape heads are held in place by means of setscrews. Turning the azimuth set screw physically moves the head in the angle shown in the illustration.
On analog cassette machines, azimuth is so important that most pro machines have a small access hole on the tape cover to permit screwdriver access to the azimuth setscrew.
Listen to this example (2.06MB WAV file) of playback from an out-of-azimuth cassette recorder, and listen to the improvement in fidelity as the setscrew is turned, bringing the playback head back into azimuth with the cassette. Quite dramatic indeed! If you'd like, you can download the same audio example as an AU file (1.03MB) , or as an ADPCM WAV file (556KB). Please note that the ADPCM version has audible artifacts, such as "halo-ing" that are a result of the ADPCM encoding.

How do I adjust azimuth on an analog cassette machine?

This is an illustration showing the location of the Azimuth Adjustment screw in a Sony TCD5 Pro II cassette recorder. Notice that the FWD (play) button is depressed to extend the heads.Many analog cassette machines have their azimuth adjustment screw in a similar location.

Simple Alignment

1. Clean the tape heads AND the tape path.
2. Using a professional demagnitizer, carefully demagnitize the heads and tape path.
3. Insert a laboratory standard cassette alignment tape.
4. Turn the adjustment screw for the maximum output levels. If these levels do not match, turn the adjustment screw where both output levels are within 0.5dB of each other.
5. Phase Check Mode: If your machine is stereo, and the outputs are connected to the X-Y inputs of an oscilloscope, adjust the azimuth screw until the scope shows the characteristic in-phase pattern.If you are using your ear to detirmine phase, listen for the point where left and right channels have the most output. If you can, combine Left and Right to make a mono sum, and then listen for the point that has the most high frequencies.

IMPORTANT NOTES!:

• It is very important to select an adjustment screwdriver that is the right size for the azimuth adjustment screw, and that the screwdriver not be magnetized. You do not want to accidentially strip the screw head, nor erase your alignment tape!
• Do not force the azimuth adjustment screw in either direction! Too loose, and the screw will pop out, along with the tension spring that holds it in place. Too tight, and you run the risk of stripping the screw hole threads.