Pros: pretty accurate, almost can't tell if its in or out of circuit:
Cons: loss of air and bass definition-small but audible
I have 2 sony 5400 cs/sacd players: sound slightly different from each other, use sennheiser 800's to listen. putting the amp in line with unbalanced leads and listening to cd's showed almost no change in sound of either player but small negative overall impression: bass boomier by a small amount, a little less air. Have no idea how it compares to other equipment or balanced leads. definitely not a $1500 improvement in my system: i'd say about a detraction when compared to front earphone jacks on the sony.