Product name: DUAD 90

Sales period: From 1978

Specs: Tape typeType III

Maximum residual magnetic flux density 1,500 gauss

Coercive force 320 Oersted

Squareness ratio 0.87

Bias 108% (standard tape deviation)

Sensitivity +2.5dB (C-60 )

Frequency response +1.0dB (8kHz )

+4.0dB (12.5kHz )

Maximum output +4.0dB (C-60 333Hz )

+7.0dB (12.5kHz )

Sensitivity unevenness 0.5 dB or less

Output fluctuation 0.5 VU or less

Bias noise -61.5dB

Transcription 55dB

Erasure 68dB

Price at time of release:¥650 (C46) ¥800 (C60) ¥1,200 (C90)

Comment: This is the second generation cassette of Sony's Ferrichrome type tape "Duad".

The magnetic material of conventional products was made by coating two layers of chromium oxide and iron oxide. It is a two-layer coating of magnetic material.

Since "JHF" for chromium position released at the same time uses iron oxide magnetic material, this product also seems to be coated with two layers of iron oxide magnetic material with different characteristics.

The cassette body adopts the newly developed "DP mechanism" (Dual Protection Mechanism). The combination of a striped sheet and a stepped hub greatly reduces hub rattling and tape winding disorder. It is said that sound quality has improved due to stable tape running and reduction of modulation noise.

The package changed to a method of printing the product name and product description on the outer film, and when the film was removed, only a simple design index card was placed in a transparent plastic case, which became the mainstream style after the 1980s. rice field.

The basic design of the package and body label is the same as that of the "JHF" released at the same time. It is gold.

After the release of this product, the ferrichrome type standard was established as "Type III", but with the subsequent spread of metal tape and the high performance of normal chrome type tape, the significance of its existence gradually faded, and manufacturers other than Sony There are many cassette decks that do not have the Type III position.

In the 1980s, the heyday of cassettes, metal tapes and HF systems were renewed one after another, but "DUAD" was a major renewal with only minor changes to the package and label notation. After all, this was the final generation.