Few areas of hi-fi are as apt for tweaking as valve amplifiers. At the very least, changing valves is easy since they almost invariably plug in and out. Alternative and/or upgrade valve types are widely available for the commonest varieties. Valves wear out, too, making replacement a maintenance job (though for most signal valves a life of several years should certainly be expected).

But how can one check the characteristics of a plug valve? Not only is it good to be able to check basic performance, but in many circuits it is highly desirable for both sections of a double triode (and double triodes are by far the commonest varieties in audio use) to be well matched. Enter the Moth Tube Imp.

It brings the power of modern integrated circuits to the business of valve testing and with remarkably little fuss allows you to test all the main parameters of normal, double triodes