The KT-S1 is a stereo cassette player manufactured by the Toshiba Corporation in Japan. During its introduction in 1981, it would have been a high-end player in the style of a Walkman. Extremely well built with a robust metal chassis and cassette compartment, one interesting feature is that it comes with a tuner module that fits into the cassette compartment to provide radio functions.
In 1981, audio chip technology had advanced enough to manufacture a mono tape recorder IC -- the Toshiba TA7628P integrated circuit (IC) -- that had built-in pre and power amplifier stages together with a bootstrap pin, and external ripple filter control pins. The IC also has a built in recording buffer amp to drive the recording bias circuit, which is not used on this model, but is used on the KT-R1 and KT-R2 recorder versions.
Since each chip was mono, two were required for stereo operation on this player. The power output of the chip is 0.6 watts per channel and powerful enough to drive a small loudspeaker, as the IC was suited for tape recorder and car audio applications. Through a good pair of headphones, this little player is very loud.
A feature of this player is that it has twin headphone sockets connected in parallel, thus allowing two people to listen to music simultaneously. It has a radio / tape selector switch, chrome / normal selector switch, an LED for the FM radio operation and a second LED for the power level indication. There is a large clear window on the cassette lid, which is very useful.
The full tape controls with cue and review facility made this player very unusual for the time. The tape deck mechanism and the push-button assembly is made of metal and manufactured to a high standard. It not only looks good but also works very smoothly.
The tape deck compartment and tape transport mechanism have a very high quality finish. The cassette compartment is blue tinted brushed aluminium plate fitted with miniature screws. The cassette compartment also houses the radio module RP-S2, and here you can see the contact points. You can see further photographs of the tape transport in this multi-page article.
Toshiba made a number of stereo players such as the KT-S2, and KT-S3 that were very similar in look and design. Many of the internal components were also identical to that used on the KT-S1. There was also the KT-R1 and KT-R2, which were the recording counterparts that used the same audio chip. On the recording versions, the yellow mute switch within the play button activated the recording function.
This player is very much on par with the Sony TPS range in terms of build quality and manufacturing. However sound wise it is more superior with the twin high gain audio chips, consequently chrome and metal tapes sound more crisp and sharp. As you will see in the following sections of this article, the design of the audio chip is unique, capable of delivering over half a watt (600 mW). However, there are limiting resistors on the PCB to reduce the output, and in this circuit application, the final output of this player is 40 mW RMS. In comparison, the Sony WM-D6C provides 30 mW / channel in a 32 Ω load.
The high power output comes at a cost, and in this case, it is the power consumption. Consequently, the batteries usually do not last as long; however, these days with rechargeable battery technology, cost is not an issue.
This was a very early 1980s stereo cassette player with a mid-sized production run. This is a good item of interest for the Walkman collector. Superbly built, most of them should still be working today with a new drive belt. The prices can vary from as little as £10 to £50 depending upon whether the seller has the original box and headphones, and the condition, as well as how many eBay bidders are interested on the day.
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Toshiba KT-S1 Inside
Toshiba KT-S1 Tape Transport
Toshiba KT-S1 Mechanism
Toshiba KT-S1 PCB
Toshiba KT-S1 Audio Chip
RP-S2 FM Radio Tuner
Toshiba KT-S1 Power
Toshiba KT-S1 Case