I have a rather unique Audere 3ZB preamp that was installed in my bass before I bought it. The bass is a G&L L2500 Tribute and I think the original owner just wanted the 3ZB option. At some later point an EQ module was installed and now it has a volume knob, mids/blend stack, and a treble/bass stack. There are two preamp modules - not a really big deal since they're small and the pots are tiny, so it'll all fit in most control cavities. The upside is that the blend has a center detente, unlike other stacked Audere blends.
The knobs are included. The LED is wired and works. There are three toggle switches on my bass - one is the Z-mode switch and the other two are coil taps for the pickups. The Z-mode switch is the only one that would come with the preamp.
One super cool thing about this preamp is the size of the control pots - they're tiny! They're really low profile in the control cavity so even though the preamp modules mount to the control cavity cover there's still room between the preamp modules and the backs of the pots. The pots are completely sealed and very high quality.
I don't use the Z-mode switch at all with this bass and would rather have two mid controls.
$150 shipped, CONUS.
Configured the way that it is, this preamp with knobs would cost about $225 shipped.
Here's a link to info about the
3ZB preamp
There's a lot of info and explanations there, and I encourage you to check it out.
Here's the long and the short of the controls and why I like it:
Three knobs Volume knob - this is an active volume. Unlike passive volume the tone won't change when you change the volume
Mids/blend stack - the top of this knob stack is mids boost/cut and the bottom part is an active blend. The pickups connect to the preamp in stereo and the blend gives you an even scan across the range of the blend. You can truly blend the two and get a 30/70 blend, unlike a passive blend.
Treble/bass stackThe top is treble and the bottom is bass. I'm not sure you'll ever need to boost the bass with G&L MFD pups, but you could. The treble control is really nice here because boosting treble adds clarity instead of hiss (like the treble control of most pre's).
The Z-mode switch (which is the one by the volume knob) changes the way the preamp "sees" the pickups. In mid-Z mode you get the normal sound from your pickups - with the EQ flat it sounds very much like your pickups in passive mode. Low Z reduces the impedance and you get deeper lows, subdued highs, and a bit of an expanded sound. High-Z is high impedance and you get a thinner, brighter tone.
Here are a few pics of how it looks on my L2500 Tribute:
