You can use an SF-2 with the F-2B, but, because there's no effects loop, it's a bit of a hassle. You'd plug into the F-2B, then take the output of the F-2B into the input of the SF-2. The SF-2 output would then go to your power amp.
The hassle from this setup is that as you increase and decrease the gain of the F-2B, you may need to reduce the input gain on the SF-2 to keep it from being overdriven. The output level of the SF-2 will then act like a master volume level.
If you don't change output volume a lot, then it's not that big of a deal. If you do change output level on the F-2B a lot, then it's sort of a tweaky hassle.
I guess you could also put the SF-2 first, then take it's output into the F-2B. If you change preamp volume a lot but leave the instrument levels fairly even, this may be a better setup, but I suspect the SF-2 would probably prefer a little hotter input than you'd get directly from the bass.
The effects loop of the F-1X has a fairly constant output level which can feed the SF-2 and returns to receive the filtered output so it's definitely less hassle (and that's why it's there after all).
This is not all exactly equivalent. In the F-1X, the effects loop is before the tone controls, so that may sound different than an effects loop after the tone (admittedly, this would be a bigger deal with something like a distortion unit than another set of tone controls).
I don't know too much about the F-2B schematic, but it may not be too hard to create effects loop points if you really wanted to go that route. Because the F-2B is an all-tube design, the proper nominal output level may not be available at an easy point in the circuit.
David Fung
