DS
A transparent-shell version resembling the final D
DYNAMIC SPIRIT
1984
C46: 370 yen.
Unlike the earlier black-shell D, this transparent-shell model looked lighter. Predominantly white packaging also created a light, fresh impression. D’s traditional red remained as an accent in fine lines.
DS: explanatory notes
DS stands for Dynamic Spirit. Released in 1984, it was an improved transparent-shell version of fourth-generation D. Its relationship to D resembled that between AD and transparent AD-S, but DS was priced at D’s level. Rather than a higher-grade model, it was another D version offering even better value.
The successful, convenient D tape was retained. Its RC・II mechanism improved mechanical-component accuracy: high-precision transparent shell sections made the remaining tape easy to see, and the transparent internal sheets had a new construction. This provided good transport performance and high reliability. Shell precision was controlled to micron tolerances, improving side-to-side sensitivity consistency, phase accuracy and other characteristics. The writing label was also replaceable.
DS and D were sold alongside each other for a while. No new D followed, however, and DS effectively became its successor.
OD
A top-grade Normal cassette with an enormous dynamic range
OPTIMUM DYNAMIC
First generation: 1979
C46: 500 yen.
The first generation appeared in 1979. It used the same high-precision shell sections as SA, with a large hub for C46. Packaging was redesigned in 1980.
Second generation: 1981
C60: 650 yen.
The second generation arrived in 1981. Its shell used the same exceptionally precise SP mechanism as MA, and the label became replaceable. The model gradually left the scene, seemingly making way for AR.
OD: explanatory notes
The model appeared in TDK’s coordinated cassette renewal of 1979, replacing ED at the top of the New Dynamic Series Normal lineup.
OD stands for Optimum Dynamic. It used newly developed Optima Ferric magnetic material. Unlike ED, this was based on ordinary gamma iron oxide: the particles were made ultrafine, their aspect ratio increased and their orientation improved. A new binder system provided high dispersion and packing density, surpassing earlier gamma-magnetite tapes. High-frequency performance matched AD, while low- and mid-frequency sensitivity exceeded it; MOL also increased. The tape offered an enormous dynamic range across the entire frequency band and the rich, expansive sound characteristic of Normal.
Metal tapes had only just appeared when OD arrived, and TDK’s MA-R was attracting widespread attention. Perhaps OD, released in these circumstances, was particularly characteristic of a company with strength in ferrites.
AD-X
A model above AD using the same AVILYN as SA
ACOUSTIC DYNAMIC EXTRA
First generation: 1982
C46: 550 yen.
Introduced in 1982 as the first Normal tape using AVILYN. Compared with AD, MOL was 2 dB higher at low and middle frequencies and 1.5 dB higher at high frequencies. Its dynamic range was the widest among TDK Normal cassettes. The shell used the same SP mechanism as MA. Its price matched SA.
AD-X: explanatory notes
This Normal cassette used AVILYN high-density-recording magnetic material, the same as High Position SA. AD-X stands for Acoustic Dynamic Extra.
AVILYN, made by adsorbing cobalt ions onto iron oxide, can be produced with freely and precisely controlled coercivity, which is related to the required bias. SA used AVILYN tuned for High Position. For AD-X, it was tuned for Normal, allowing the same bias as AD.
AVILYN greatly improved electromagnetic conversion characteristics, including maximum remanent flux density. It delivered detailed, accurate sound with high resolution and an information content comparable to SA. Development emphasized listening evaluation, called Acoustic Concept, as well as electromagnetic performance. The sound was reportedly improved using AD’s listening characteristics as a starting point.
Second generation: 1988
C46: 450 yen.
The second generation was updated in 1988, almost six years after the first. Ultrafine AVILYN provided high MOL comparable to Metal tape. It used the low-resonance SPR mechanism, an H-shaped window and multifaceted shell joints. Its price now matched the new High Position SR.
Third generation: 1989
C46: 430 yen.
The third AD-X generation was released in 1989 with a completely different design. New Non-Pore AVILYN improved the tape’s capabilities further. Flash Surface Form gave the shell sections an all-round rounded shape pleasant to the touch.
Fourth generation: 1990
C46: 430 yen.
The fourth generation appeared in 1990 with entirely redesigned packaging. Non-Pore AVILYN provided low noise and high signal levels. Reliable tape with elongation variation no greater than 0.01% supported repeated use, alongside Flash Surface Form shell sections and a rounded case.
Fifth generation: 1992
C46: 470 yen.
The fifth generation was released in 1992. For outdoor use, including car audio, it adopted the new rigid, vibration-resistant AR・RC shell, joined by both screws and ultrasonic welding. Reliable, low-stretch tape was suitable for repeated use.
The original AD-X was priced at SA’s level, with the same shell mechanism and other components. It was initially perceived as a Normal version of SA. AR-X later took that position, while AD-X became roughly equivalent to SR.
For boys of the time, it was also an agonizing choice: buy High Position SA or Normal AD-X?
With this model’s arrival, each of TDK’s principal tape-position representatives, AD, SA and MA, had an -X variant one grade higher.
First-generation AD-X advertisement from 1982: You can hear the precision of the mechanism. ACOUSTIC CONCEPT AD-X.
The pursuit of precise, even head contact led to the dual-spring pressure pad.
AD-S
A fresh transparent-shell appearance: AD-SPLENDOR, an improved AD
ACOUSTIC DYNAMIC SPLENDOR
First generation: 1983
C46: 500 yen.
The first generation was released in 1983. It used the same tape as third-generation AD. Not only the shell sections and internal sheets but even the reel hubs were transparent.
Second generation: 1984
C46: 500 yen.
The second generation arrived in 1984 alongside fourth-generation AD, whose tape it now used. It was a version of fourth-generation AD with the SP-XC mechanism.
AD-S: explanatory notes
The S in AD-S means Splendor. As its name suggests, it was an AD derivative with an improved shell mechanism. The tape remained the same as AD, but the shell sections and other components were entirely different: the new SP-XC mechanism was used.
It featured special transparent plastic shell sections suppressing resonance, transparent sheets ensuring stable tape transport, Dual Mold hubs with still greater circular precision, and a dual-spring pressure pad giving uniform pressure at the required tape-contact point. By carefully suppressing transport’s harmful effects on sound, it reportedly achieved more clearly defined sound images as well as rich, transparent sound. The clear shell seemed to make those qualities visible.
Comparing its sound with AD allowed listeners to hear for themselves how shell differences affected sound. It was priced 50 yen above AD.