Noisy Drive train, whats the cause?

m00nd0g

I am currently building up a CAAD9.
Using what parts are available and replacing parts when required.
I have a pair of Fulcrum3s brand new Ultegra Cassette (9 speed)
My mechanic said the Tiagra chain did not require replacing.
However the drive train is noisy.
Do you think the chain needs to be replaced?
Could I have fitted the cassette incorrectly?
Could it be the wheels?

sungod

if the one/both derailleurs are out of adjustment that can result in the chain catching/rubbing on cassette/chainrings

if i'm fitting a new cassette i always fit a new chain, otherwise the cassette will wear faster to match the old chain

SNACK-HEAD

learnt the hard way , took me weeks to put the jockey wheels facing the correct direction , like the arrow shows.
Solved one of my many problems.