I bought most of the Doepfer filter modules, and this is by-far my favorite. I didn't think that I'd like the bass response dropping off as resonance was increased, but I LOVE IT. I feel like this actually defines this filter. The adjustable sonic range on this is huge, when controlling level & resonance. I liked moog filters on softsynths & digital synths, but I LOVE this filter & authentic moog filters. There's a night & day difference between this & a digital emulation. It must be the way all of the transistors interact with one another as the resonance, level, and frequency is changed. Many digital emulations don't account for all of these minute differences. This thing really delivers. My only complaint, if any, are the knobs are a bit rough (hard on the hands to twist a lot). I'm tempted to replace them with a more comfortable knob, but I'd lose the classic look.