Reel-to-Reel Record Head Alignment

On the AKAI GX-280D, the recording head has three adjustment screws, meaning both the height and the azimuth can be adjusted. The azimuth is how much the angle between the head gap and the tape varies from 90 degrees. You want zero azimuth angle, that is the head gap and the tape should be perpendicular to each other. You typically play with all three screws for height adjustment and just the one screw that's off to the side for azimuth. In the following, we are going to focus on the azimuth adjustment.

When the azimuth is not zero, the left and right channels are out of phase and the best way to visualize out of phase left and right channels is to do a phase analysis and display the so-called Lissajous curve. When the curve is reduced to a diagonal that looks like a forward slash (/), the two channels are in phase and that's what you are aiming for. The audio editing software cool edit pro enables you to view Lissajous curves (phase analysis), which means we will have no problem aligning the recording head for azimuth. If your audio editing software does not have this phase analysis capability, you may have a hard time properly adjusting the azimuth just by ear (although it's quite possible to do so).

What you want to do is record a tone with the recording head, play the recorded signal and feed it (via the headphone jack or the audio line-out) to the audio editing software for phase analysis. All this is done at the same time since anything you record on the reel-to-reel deck can be played by the play head as the tape passes from the record head to the play head, assuming you don't forget to switch from source to tape.

It seems that all we need now is a tone to record on the reel-to-reel tape deck. Well, that's quite easy to obtain from the audio editing software: generate a stereo tone at a given frequency and save it as a wav file. For azimuth alignment purposes, you need a tone at 1 kHz and one at 10 kHz. Burn those two tracks on a CD and you are good to go.

So, the procedure is as follows: pop the CD with the two tones in the CD player (connected to the audio line-in of the reel-to-reel), play the 1 kHz tone, record using a fresh tape and forward the signal coming from the play head to the audio editing software. Turn the azimuth adjusting screw (a little at a time) until you are satisfied with the shape of the Lissajous curve. Then it's time to switch to the 10 kHz tone and repeat the procedure for fine tuning (might be harder this time because of the much higher frequency).