Sony WM-33

Sony WM-33

The WM-33 was a stereo cassette player walkman manufactured by the Sony Corporation. A red Walkman is a very desirable item amongst collectors. It is an iconic design that sold well because of its square proportions and smart impressive markings on the cassette lid. The three band graphic equaliser and the printed graphics gave it a high tech look that was very attractive to buyers. The construction and finish of the plastic was good, and an unscratched new one looks very nice, because it is an all-plastic construction with a brushed aluminium strip at the front.

It has fast-forward, rewind, and play tape controls. The push-button mechanism is of course plastic for this budget-end design, and therefore you should use it carefully.

The WM-33 uses the Sanyo LA4570 IC, which is a successor to the Sanyo LA4520 audio IC. It is a very good chip found on many cassette players, including the Sanyo MGR59. The sound quality of the WM-33 is good providing you ditch the headphones that came with it and use something better.

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Graphic Equaliser Design

Graphic Equaliser

Since the LA4570 IC has separate preamplifier and power amplifiers blocks, they decided to connect a graphic equaliser between them. From studying the circuit, it certainly appears that the skew points are off thus narrowing the frequency response. Consequently, I modified mine by changing the filter capacitor values, which improved the sound quality drastically.

Servo Motor

A great feature of this Walkman that most people did not know about is that it uses an analogue closed loop servo IC to drive an advanced motor design similar to that used on the Sony WM-BF22. When you listen to this player, you will notice straight away how smooth the tape speed is. Sony has always been the leaders in innovation and it is a big improvement from the cheap d.c. motors that were commonly used by other manufacturers of that time.

From an electronics point, this Walkman was a major technological leap forward for Sony and the components they used here marked a new era in design engineering for some of the later models. Once Sony started to improve the motor design, they also began looking into power management functions for the motor. This refinement enabled later generation of Walkmans to operate for longer periods on just a single battery.

I love the clean lines and colouring design of this Walkman. The Sony logo is in a silver-mirrored finish, which looks nice compared to the modern one.

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Sony WM-33 Sony WM-33
Sony WM-33 Inside
Sony WM-33 Tape Transport
Sony WM-33 Mechanism
Sony WM-33 Chipset
Sony WM-33 Graphic Equaliser
Sony WM-33 Power