How I lowered my speakers noise floor by 6db

As many of you know, I use Behringer B2031A amplified speakers plugged directly to my soundcards' line level output, with software based volume control and a custom cable with a 3.5mm headphone to 2 x 1/4" jack cable.



They sound completely awesome I love this set up so much. The only little thing that bugged me was that I can hear the noise floor of my soundcard at louder slider settings. If I turned them up for quiet material or for stuff with large dynamic headroom the white noise was just perceptible.

The SB Live wiki page has an uncited note that "the original SB Live! had a very low noise floor for its time". Doh! I considered getting a better soundcard with balanced outputs to lower the floor, but meh - money, linux support etc. just for something that is so minor and uncommon.

In practice, I usually stay within something like 2-10% of max signal level from my soundcard on the speakers, and the noise floor is far below hearing level.

I recently realised that I had the input trim on each speaker central at 0db, but they could go to -6db. By setting both speakers to this, I am forced to have a higher output signal from the soundcard to compensate. This makes the soundcards' signal to noise ratio much better (by 6db!) for any given actual listening level. Of course, my 100% setting is also 6db quieter, but I dare anyone to site in front of these at 100%!

So now I probably use something like the 20-40% signal level, with plenty in reserve should I wish to wind something up loud. This is a much more sensible use of the range, as I was right at the bottom 1/4 of the mixer sliders most of the time. I can't hear the sound floor, even with everything at 100%/max/11 !