K8084 problems

I have a perfect working K4004B but no i want to connect my new K8084 and there are a few problems:

There is a enormous hum (even when i move the power supply a meter away)
The sound produced is very, very soft (you must put your ear on the speaker to hear it)
The sound produced is full of cracks an other noise.
and when i switch off the power there is a huge bang through my speakers

I have checked the soldering and had it checked by someone else they seem… fine
i have checked the cables and connectors
I have tried different sensitivities on the K4004b
i have tried the k8084 on another k4004b (same result)

Looks like a power supply problem.
How do you power the K8084? Detailed description or diagram please.