Planet Sinclair


x The Machines
x Machines: 1970s
x The Black Watch
x Cambridge / Cambridge Scientific
x DM1 / DM2 / DM235 / DM350 / DM450 / PDM35 / PFM
x Enterprise /
Enterprise Programmable
x Executive /
Executive Memory
x MK14
x Oxford 100 / 200 / 300
x PP3
x President
O Active Filter Unit / Project 605 / Project 80 / PZ8 / Q16 / Q30 / Stereo FM / Super IC-12 / Z-50
x Scientific / Scientific Programmable / Scientific Programmable Mk 2
x Sovereign
x TV1A / TV1B / MON1A
x Wrist Calculator

Last updated
12 Feb 1998

Hi-Fi Equipment: 1970s

Sinclair began the 1970s much as he had the 1960s, producing cheap hi-fi equipment such as amplifiers and tuners. Although they were very inexpensive, the quality was (perhaps inevitably) occasionally not what it should have been.

Active Filter Unit, PZ8, Q16, Stereo FM Tuner

These were all add-ons for the Project 60 hi-fi system, launched in 1969. They were, respectively, a tuner, an amplifier, a loudspeaker and another tuner. All were launched between 1970 and 1972. The tuner came as a complete chassis and fascia which needed only to be put in a box; the Q16 was simply a version of an earlier loudspeaker, the Q14, which had been smartened up with a teak surround.

Project 605

Launched in 1971, this was a further development of 1969's highly successful Project 60 hi-fi amplifier. Sinclair's advert read:

The easy way to buy and build Project 60

Project 605 is one pack containing one PZ5, two Z30s, one Stereo 60 and one Master Link. This new module contains all the input sockets and output components needed together with all necessary leads cut to length and fitted with neat little clips to plug straight on to the modules. Thus all soldering and hunting for the odd part is eliminated. You will be able to add further Project 60 modules as they become available adapted to the Project 605 method of connecting. Complete Project 605 pack with comprehensive manual, post free, 29.95. All you need for a superb 30 watt high fidelity stereo amplifier.

This was about half the price of a comparable ready-made amplifier at the time. The Project 605 was a well-designed piece of kit and sold well.

Project 80

Launched in December 1973, this offered all the same facilities as the Project 60. It brought the earlier design up to date with a black anodised aluminium fascia and sliders rather than knobs (though sliders, people soon found, caused ear-splitting crackles when the dust got into them). The power amplifier had been slightly uprated. The big feature of the Project 80, however, was its "non-obtrusiveness" - it could be built into a book end or the base of a lampshade (see right), amongst other slightly weird ideas.


The Q30 was an unusual 'planar' speaker, launched in the autumn of 1972. It used what is known as the 'infinite baffle technique'. It was given an extensive review in Hi-fi Answers and compared with the Goodman's Planax 2 although in fact they were not technically comparable. Q3Os were unusual eye-catching speakers which measured 331/2" wide by 231/2" high by 4" deep - a little inconvenient for anyone other than the hi-fl enthusiast or someone with a very large room.

Super IC-12

The Super IC-12 "high fidelity monolithic integrated circuit amplifier" was launched in June 1971. Its curious appearance was due to the addition of an enormous (compared to the size of the chip) heat sink, which led to the device being nicknamed "the hedgehog". For its advertisement, the Super IC-12 was photographed next to the newly-introduced 50 pence coin.

System 4000

The System 4000 amplifier received a very favourable review in Tape Magazine of June 1974. It looked very like the System 3000, but the entire circuitry had been redesigned. According to the reviewer,

The test result table shows that, in almost every area, the amplifier exceeds its manufacturer's specification. At the time of testing it was mistakenly thought to be a 20 watt amplifier. None of the figures gave any reason to doubt this and only when checking the price with the manufacturers did it emerge that the rated output was only 17 watts rms power.

For an amplifier intended to produce 20 watts per channel the results would be good; for one of 17 watts rating they are generally excellent ...

This is an amplifier that I would buy for myself if the manufacturers could sort out one or two minor problems with production. As it stands, the System 4000 is a triumph of engineering and design over production quality control.

This was to be a familiar story in later years!


The Z-50 amplifier was added to the Project 60 range in June 1970. The Z-30 was rated at 30 watts, so Sinclair decided to advertise the Z-50 as rated at 50 watts. However, they blew at between 37-40 watts, so their designer suggested 30 watts as a rating; the final compromise was 40 watts. Not surprisingly, the Z-50 did not prove completely reliable in use.