Jason & I headed over to Wayne's today and listened to the RCA inline bybee filters and also the speaker level Bybee filters in Waynes system today. The speaker level filters were an obvious and immediate improvement over the plain speaker wire hookup. When listening to Natalie Merchant singing "Ophelia", with the Bybee's, the sound was less vieled, instruments had better seperation, better depth to the soundstage, cleaner and more relaxed treble, and the bass did not drone as much (the bass on this track is definitely on the "drone" side of things, but it's the recording's fault). A nice improvement, but one I was already familiar with, since I had a similar result using bybee'd speaker bi-wire jumpers in my own setup.
Next up Wayne inserted the RCA inline filter to the digital input of his DAC. It was similar to the improvement from the speaker level filters, except even more so. In the intro of Ophelia, you could hear that Natalie was actually singing gently, as opposed to just sounding softer. The middle portions of notes and vocals filled in very nicely. The music just flowed beautifully. One interesting thing I noticed - without the bybee filter, you could hear the primary event of her singing, an then you would hear the reverb way at the back of the room, but it was almost like there was a gap. With the bybee inline, the primary vocal and the reverb "connected", so that there was a sense of continuity between her in the front, with the sound travelling back and then reverbing as a single continuous event. It took me a while to figure this out (I knew something was different, but it was difficult to put my finger on it). Last but not least, the bass sounded much better. Instead of a single droning note, it was obvious that there were actually 2 notes being played sequentially, one being lower and more visceral than the other.
Next, Wayne put a filter on the digital output of his DVD player in addition to the one we had on the input of the DAC. The results were mixed, IMO. The treble was cleaner again, and even better instrument seperation. But, I thought her voice lost some body, and the overall sound was more "hifi" and less natural. It was an "impressive" sound, in that it did a lot of individual things "right", but the music just didn't quite flow like it did with a single bybee.
Then the bybee was removed from the output of the DVD player and was put in series with the filter at the DAC input, so that we had to in line, one after the other. To my ears it sounded exactly like the previous setup with the filter at the DVD digital output.
So, what was the result of all this listening? I bought the Bybee RCA inline filter of course

Took it home and hooked it up immediately. I think it made a bigger improvement in my system than what I heard in Wayne's system (I love it when that happens).
The results we heard w/multiple bybee's inline may simply be specific to Wayne's system, or what we heard as "trade-offs" may be judged quite differently by other's in their own systems, so the best idea is to try it out, it takes all of 30 seconds to plug them in or out of the loop. . .