made up a kit of 200watt amp K8060( from UK) used heatsink as specified and also 230volt transformer with 2 x 30volt ac outputs.
all worked first time and bias set to approx 10 millivolts as per spec.
my problem is some mains hum at all levels of gain control. using mini coax screened cable to input pins on pcboard.
i have fitted this kit of parts into an aluminium box size is 188 x 188 x 63 mm.
no amount of rearranging the leads mains side has helped, even twisted them as pairs, i.e mains and both 30volt outputs.
changed to large caps at 4700uf but still the same.
any ideas at all. spent a lot so far etc. time not a problem. thanks 
Short the input. If the hum is still present, it is caused by an assembly problem, if not, it is caused by wiring.
I had this problem on my amp initially. It was actually due to a poor grounding issue. It worked great in the open air but I got the hum as soon as I installed it in the chassis. It was cured when I connected the Ground of the circuit to the chassis.