is the 404 og supposed to have hum at full volume, and some hiss , only when no samples are playing, i notice it more now then before, not sure if it is from overloading the mic input for cool overdrive sound design. it also hums and hisses with batteries

did you try cancel+start/end+cntrl knob 3 to increase output db? for me, hiss seems to come up when the volume knob is turned past 3 o clock. with +9 to +12db I don't need to turn it up that high...

thanks for sharing your idea, using 404og at full volume will give you maximum headroom and minimized distortion if you are not using compression, this extra head room allows for deeper and cleaner subsonics, this will also reduce your overall loudness, then adjust the loudness of your subsonic to fit the mix of maximum headroom. How ever to avoid any noticable hiss and hum from having the master volume maxed out, I found that 3/4 is a more comfortable level and some people recomend half. half volume with full compressor volume sim seems to be the loudest also being a bit noisy, so to recap and highlight,

full volume = hiss and more headroom.

half to 3/4 full = loudness and distortion .

the audio wave files that the 404 exports can be treated and mastered for broadcast quality, in any software and the hiss can be filtered, i might still adjust the internal output volume that you describe, and see if any other characherists of tone or clarity can be achieved.

It also could be electro-magnetic interference caused by the way you run power to your sp.