I currently have the transformers fitted. They are these: Sowter Type 5069. I have 250r on the primaries, bypassed with 220pf, 680r across the secondaries in line with 1n. I have tried adding 200pf from the primaries to earth. The opamp section is completely disconnected and the +/-15v is not connected.

The hiss is only present when there is an input and is not volume dependant. There is none (or almost none) when using opamps.

The schematic for the board is here: http://valwalker.co.uk/misc/4398X2Bv1.pdf

I am guessing that either I need a filter somewhere or this is power supply noise.

Any ideas please?

Thanks

Val