In past years I have calibrated many tape decks including 2 head and 3 head. Once I had a Tascam (teac) calibration tape..(lost it somewhere). Many a times when you buy a 3 head tape deck from open market unknown (who was previous owner) you end up recalibrating it. If you don't have a professional tape how to go about it?. First you need a prerecorded cassette from a known brand on which you will set it usually recorded from one of your previous machines you bought new or you know they were never adjusted. Here is step by step process I go about it.. 1. play the tape and adjust azimuth using yr ears or a 8kHz/ 16Khz level display on spectrum analyzer - hear the tape on calibrated deck and the deck your calibrating, for minimal difference in sound. 2. use a blank tape - record and adjust record head azimuth on best sound on adjusted azimuth playback head and play also on another calibrated machine, I usually use 3 machines for balanced result. 3. after settings heads you set levels, I do it opposite way for levels, by recording at 0dB and play on another machine to see levels. ( you may need to do same for type1, type2 and type4.) 4.. adjust record levels inside on board. once you got record levels set at 0dB played on different machine you know recording will sound accurate. 5. now you set playback levels till both decks display close and balanced left and right. 6. match tape / source levels- these will fit in perfect., if they don't you go back and readjust the error on record levels