Been looking into getting a three band EQ to put into a bass with room for four knobs a la active P or active J basses. Pickups to stay passive. What do I look for? I know I'll need one of them stacked so I'd end up running two volumes, plus a stacked knob and a single knob for the bass, mid, and treble. Are most preamps sold with or without the volume pots? What should I be looking for as far as the number of pots that come with it. I found a Duncan unit but it looked like it only had one volume knob, am I able to add a second (this is all new to me, active EQ internals). Do I look for one with just the stacked and single EQ pots? How about a balance knob instead of two volumes, is that a good idea with passive P/J pickups? Are there certain models that can be defeated to passive mode with a push/pull pot or can they all be bypassed? Help a brother out.
If all you want is a three band active EQ, most preamp manufacturers have a 4 knob version. Some, like EMG, even have a 3 knob version with all stacked controls. You can pretty much get any preamp you want with 4. Just read the description of each model before you buy. Some also have the option of Volume/Volume or Master/Balance, so that's another thing to consider. A typical 4 knob setup is volume, balance, bass/treble stack, mid/mid sweep stack. They sometimes, but not always, come with volume and balance knobs, but you usually use the existing ones if they don't. Active pickups require a different set of volume pots than passive. Passives usually use 250k or 500k volume pots. I'm not 100% sure about the exact numbers, but think actives usually use 25k or 50k pots. So make sure your volume pots work with your pickups. Some pres include a bypass switch, and most can be modded to have one. Your pickups must be passive for it to work though, so no EMGs (except HZs) or Blackouts.
http://www.bestbassgear.com/bartolini-preamps-ntmb.htm http://www.bestbassgear.com/aguilar-obp3-preamp.htm All you need to know.
The Audere Classic could do that with either 3 or 4 bands. I have the 4 band configured as VOL-BLEND-Stacked Bass & Treble, Stacked hi mid on top of low mid. Installed in a Guild Pilot fretless 5. I like that setup a lot as I can grab either set of stacked controls with one finger and cut or boost for a macro adjust and of course the 2 mid bands is slightly more flexible. I believe it can be wired up as a 3 band as well. It's a great pre and when you consider the price tag it's suiper competitive. If you could live with 2 band, I have a 4 knob Aggie OP-2 that I'm pulling out of another Guild Pilot 5. I'll be replacing that one with another classic. The Aggie is very warm, very crisp. Kinda 2 band Stingray'ish to my ear. I like more detailed control over the mids... I often have 3 basses cabled on stands this time of year. Gotta do something with all that extra outdoor stage or oit will get filled up with guitars and we can't have that now can we ? So having mid's control on board is mandatory for me. That way I can set my rig for 1 passive and adjust the active basses to suit... And the low mids, there is where the rubber meets the road in my setup. Of I can get that right, everything else will pretty much fall into place.