Does amp output V decrease by adding gain stage?

Is that the input sensitivity? Balanced or RCA? You might need one hulk of a preamp.

That is RCA input. So the amp can mate with a giant preamp to take at least 4 Volt out to drive the amp. I am thinking to put gain stage(s) in the input of the amp. So the question is if I add gain stage(s) to the amp, does it mean the input voltage of the amp will reduce below 4 Volts?

Yes, adding a gain stage at the input would reduce the voltage needed. How much less voltage depends on the amount of gain that you add.

To get to a 1 volt level you will need to add 12db, which is easy with most tubes that might be in a gain stage.

Make perfect sense. Thanks gents