Hitachi 3-Head Design

For the best audio quality, a 3-head system is usually the ideal choice. In a 3-head system, there is a dedicated erase head, a recording head, and a playback head. The reason for having separate heads is that the gap has to be different for each function. This gap that audiophiles usually refer to is the one between the magnetic poles, and for recording purposes, a wider gap is required, whilst for playback purposes, a narrower gap provides the best frequency response.

Since the design of the compact cassette was for a single record/playback head, only a single narrow window and pressure pad exist in compact cassettes. Consequently, most designs have been limited to a single gap design responsible for both recording and playback. In these types of designs, the head-gap is optimally set for the best recording and playback quality; however this is a compromise in performance quality.

In this article, we see that Hitachi engineers have designed an ingenious way of including a recording gap and playback gap within one Siamese unit. The separation between the gaps is approximately 1.4 mm, thereby allowing the single pressure pad of a compact cassette to be most effective.

Hence in these designs, a wider gap for recording provides a stronger magnetic imprint on the tape, and a narrower gap for playback extends the higher frequency response. Another advantage of separate gap design is that monitoring of recorded audio can be live, where the sound engineer may be able to listen to the actual recorded signal from the tape.