FWIW TWL and Gmood1's comments seem to be nearly on point....
However I cannot tell exactly what you is doing with this integrated unit when you say "I try using it as a direct amp.....try it as an int amp"..... Could you elaborate for me. Are you saying that you disconnected the amp section from the preamp section and drove the amp section with a source that had its own volume control?
Assuming that it is being used as it was intended, that is the pre-amplifier section connected to the amplifier section, what you are hearing is the residual noise level of the pre-amplifier section or the pre-amp section tubes. It doesn't make any difference whether or not the volume control is minimal or maximum as the VC preceeds the pre-amp output to the amp, in other words its out put is steady at all times. With very efficient speakers you will usually hear some hiss, especially when your ear is near the speaker. Power tubes generally do not hiss and the power section of the amp (or a seperate power amp) should be hiss/hum less under optimal circumstances.
If its a big deal for your sonically, you might try replacing the pre amp or driver tubes with some very quiet low noise tubes. It might help.
However I cannot tell exactly what you is doing with this integrated unit when you say "I try using it as a direct amp.....try it as an int amp"..... Could you elaborate for me. Are you saying that you disconnected the amp section from the preamp section and drove the amp section with a source that had its own volume control?
Assuming that it is being used as it was intended, that is the pre-amplifier section connected to the amplifier section, what you are hearing is the residual noise level of the pre-amplifier section or the pre-amp section tubes. It doesn't make any difference whether or not the volume control is minimal or maximum as the VC preceeds the pre-amp output to the amp, in other words its out put is steady at all times. With very efficient speakers you will usually hear some hiss, especially when your ear is near the speaker. Power tubes generally do not hiss and the power section of the amp (or a seperate power amp) should be hiss/hum less under optimal circumstances.
If its a big deal for your sonically, you might try replacing the pre amp or driver tubes with some very quiet low noise tubes. It might help.