An SF-2 also works great for regular guitar.
 
Bill, tgo

it works amazingly with synths too.

I'm still thinking about putting my SF-2 directly inside my Starfire. It's got an ACG preamp in there now, which sounds great, but the frequency sweep isn't quite enough and you can't blend back in the unfiltered tone (which I think is crucial to the SF-2 magic).
 
 
Edwin

I would like to see pictures of that!

Here is my old Guild Starfire with Pluto Filters.I sold this Bass around 1978.

Gooollly, I guess you can fit an SF-2 inside there. But then you couldn't use the SF-2 on other instruments, but it would be pretty cool.

Yeah, that's pretty much it. I've found that I don't use it that much on other instruments and it would just be great to have it all in there.

I could imagine an SF-2 in a bass would sound amazing. Will you be  using the Series instrument PSU to power it?
 
 
Jazzyvee

I haven't worked out the power requirements, but as currently designed (no pun intended!), it uses a 15 volt power supply that seems a little less robust than the Series power supplies. However, if it ever happens, I would probably just build something that seems appropriate.
 
I've also been thinking about how to work the signal flow, whether to mix the pickups before the filters or have one filter per pickups (which seems like the better way to go). There might be switching I could do that would be able to go both ways.

Maybe there is room in a Gibson RD bass after pulling the Moog electronics out?

The SF-2 is so cool! For one thing, it provides such a beautiful deep bass with the low-pass filter. Using one of the filters in hi-pass mode, you can get some great, sparkling highs that you didn't even know existed! (Well, you knew if your bass was an Alembic, but as someone else posted the SF-2 can bring out sounds in other instruments that are impossible otherwise) The band-pass filter lets you focus in, for example if there are some mid-freqs you want to accentuate.  
 
I have a recording of my Rickenbacker 8-string that just isn't quite jumping out in the mix, so I'm going to experiment with routing the signal through the SF-2.

Harry,
 
I have found the band pass is also excellent in the low frequencies, somewhere around 80 to 100 hz can really bring out a tight low boom. I don't know how wide the pass band is but at that setting it seems like it is affecting to the low E at least.
 
JBY

JBY that's a great idea! I've generally just used the low-pass filter for the low frequencies, but then you are boosting sub-bass frequencies that aren't even necessarily useful.
 
I did the re-recording of my Ric 8-string - here's a pic of the settings I used:
 

 
The filter setting that got cut off on the right was set to high-pass.

Thought I would post the two videos so you can hear the difference:
 
original
 
new & improved SUPERFILTER version!
 
Volume is probably also a factor - for some reason I was shy with the bass volume when I made the original video, but I think you can also hear the increased clarity in the second video. For best results listen on headphones or good speakers, although part of the reason I redid it was so that it would sound better on computer speakers.

Yeah Harry -
The new and improved is sweet.
I have been hinting really hard to Santa that I need an SF-2.