The SF-2 as a pre-amp works well for me but using it is not as straight forward as I hoped it would be. I think it's harder to use as a standalone than in the send return look. Here is my take on it in my use and I accept I may be wrong in what I'm hearing compared to how it's supposed to sound. Firstly I only use it as a standalone pre-amp when playing reggae and I've not tried gigging it with other genre's because I found it too hard to make tone changes at the bass on the fly as the SF-2 seems to be the filter that is taking charge so I can't really hear it much.
For reggae I'm only generally dealing with the frequencies below the bass guitar filter cut off point so around 200 to 100hz that enables me to get some more heft and I keep the filtered signal about half the level of the unfiltered signal so that I can hear some of the upper frequencies to help with hearing my pitch clearly.
When I use it in the send/return loop of my F1-x for other gigs it is much less bossy with the sound and I can much more easily set it up in a way that allows me to control the sound more from the bass than having to make changes from the SF/2 or F1-z.
A superb piece of kit though but you can easily ruin a speaker that can't take a lot of bottom end with it. Don't ask me how I know that... :-)
