I tried an experiment this morning. I sent the tube pre section out to my el cheapo but zero noise t-amp and the hiss went down considerably. T-amp is 15 watts, integrated is 150 watts, speakers are a super efficient 104 db Klipsch LaScala.Was the hiss still too high to be acceptable?
Have you tried a different set of speakers with a lower sensitivity? If the hiss is still unacceptable with different speakers, then it would seem that there is a problem with the VincentÂ’s preamp. If the preamp does have a problem, then doing anything else makes no sense until it is repaired.
Mezmo makes a valid response about tubes, however the Vincent uses 3 tubes, one that is common to both channels.