Test Equipment

My Audio Probe / Signal Tracer is based on this circuit.  The difference being that I use an a oscilloscope probe as an input and an old Sansui HIFI amplifier (with one channel broken) as an output.

A Variac is special type of transformer that supplies a variable AC voltage.  A variac usually has a big control knob which when you turn it gives a voltage between 0 and 240V out. Why would you want that then?  Well with valve amps having lethal voltages all over them it is useful to have … Read more