The X-20 was much better than its precessor: it was putatively rated at 20 watts and it would indeed deliver 20 watts, but only with its dying breath, for the output transistors that arrived for manufacture were somehow never as good as the prototypes supplied for development. In any case, Sinclair already had a 10W amplifier: the new one obviously had to be better because it was more expensive! Apart from this, the X-20 was a good amplifier. There was none of the unpredictable performance of the X-10, no two of which ever behaved in quite the same way. Later - just about the time at which the X-20 was discontinued - larger output transistors became readily available. Some of these were tried in the X-20 and it gave 20 watts without the slightest troubles or sign of distress.

The X-20 was heavily trailed in advertisements through the summer of 1965, with double-page spreads trumpeting "in step with the SPACE AGE!" in rather wobbly lettering backed by a drawing of the Post Office tower. Only a year old and 619 feet high, the tower symbolised London's step into the space age; not only did it handle satellite communications (indirectly); it had a revolving restaurant. The adverts declared that the X-20

OUTDATES EVERY HI-Fl AMPLIFIER TO DATE

The Sinclair X-20 enables you to enjoy for the first time ever, the advantages of using a high power, high fidelity audio amplifier truly in step with today's space age electronics . . . and it is easier to build and install than any amplifier you have ever owned. Best of all it costs far less.