A couple of more thoughts – i’m presuming your preamp is making noise with no inputs connected (open RCA’s), if it only produces hum when an external source is connected then the grounds of the two devices are interacting and often just connecting a quality source will fix this problem.
Also all of our Kits come with quality components – but when it comes to filter capacitors we use the best high quality capacitors we can source – which means Nichicon or other Japanese Manufacturers. Yes they’re expensive – but they’re worth every dollar. Same goes for coupling capacitors – Solen makes excellent quality coupling caps – that are reasonably priced.
