Sound volume in computers is regulated by software, and there are a lot of programs that control de volume, so it's quite easy, in my experience, that some program changes the volume and you don't realize it. Or you simply set the volume at 100% for some application and then play music using another program and discover 100% it's way too loud for that application due to amplification or different sensitivities along the signal path or whatever. When playing audio from a computer, I never use the analog output, always digital at 100% and then attenuate externally. It's just my experience, others may be fine connecting the computer output directly the amp/speakers input. I don't, it's too risky and time consuming.