It's a bit hard to describe, but it sounds "thin" or maybe scooped in the mids. It seemed to emphasize a grating sound quality, and reduce fullness. The SM Pro passive potentiometer in comparison sounds somewhat fuller and smoother. It's kind of subtle, but my ears can tell the difference.
The DC-1 preamp could work in a pinch, but, I am being a perfectionist about my sound.
Part of it is just that I'm so used to the sound of the SM Pro attenuator I've just come to like that sound. I like that little extra fullness. Maybe "bad" is too much of an exaggeration for the DC-1 volume attenuator. It might even be flatter, actually.
You know what I bet it is a flat frequency response. Sounds kind of like "how a CD player is supposed to sound." I won't call it bad. I am just always on a quest for fullness. It's funny that I'm finding that in a $100 passive attenuator. The M Patch has this cool smooth, soft kind of sound.
I think I just got flipped out going from years listening to the same attenuator, to something completely different. I think I need to spend some time with the DC-1 and get comfortable with it as a preamp.
Thanks for the question, it got me to go back and A/B again.