The Type I Normal Bias Audio Cassette

The Type I normal bias audio cassette was the standard and most widely compatible tape format – the direct descendant of the original compact cassette. The tape preserved sound by means of a ferric-oxide coating, and first appeared on the consumer market in the mid 1960s. Heading the post you can see a fairly early Type I musicassette demonstrator, which was used to help drive the cassette format into wider use in 1970.

Sony AHF 90 Audio Cassette (1981)

The Sony AHF was an excellent normal bias cassette from the renowned hi-fi manufacturer.

At the dawn of the 1980s, there were three normal bias ferric oxide tapes in the Sony range.

The CHF was the basic offering. Light on treble definition, fairly noisy, and low in price – but in its class, still pretty good value.

The next step up was the BHF. This had noticeably better treble response, and whilst noise/hiss wasn’t exactly minimal, it was certainly more under control than with the CHF. The price was typically around 30% higher than that of the CHF.

Stepping up again to the most expensive Sony ferric, you found the technically superior AHF.

Akai SX90 Audio Cassette

I can’t, unfortunately, give much information about the period of manufacture for this Akai SX 90 audio tape. I’m guessing it’s not any earlier than 1987, and it can’t be any later than 1999, because that’s the year the cassette was given to me. Sorry I can’t be more specific.