Are there any "Pure" Outboard Preamps out there???

Personally I love the Sadowski outboard preamp. The new MXR preamp pedal seem clean and transparent. Definitely nothing from Sansamp if you need something transparent. The Aguilar preamp is based on their onboard preamp and is a fantastic one too.
Now, keep in mind that the same preamp onboard vs outboard does not sound 100% the same due to the loss of bandwidth through the cable.

 

Plenty of manufacturers sell their onboard preamps in outboard form. If there is a particular preamp that you like, which isn't available in outboard form, then it would be extremely simple to make it an outboard preamp, by installing it in a stompbox enclosure.

 

Yes a bass eq works too but what is the difference between that and tweaking your amp? Unless you just need to switch between two different bass sounds.
It depends on what you really miss about on-board preamps.

 

For this purpose this would be ideal then. Those guys make excellent quality products

Radial Engineering Tonebone BassBone | Reverb

 

These are the ones I have experience with:

Sadowsky
F Bass- Big F Boost
Fodera- Model 2011
Mountain King Electronics- Behemoth I
Mark Bass- Super Booster
Tri Logic II
Eden- WTDI
BBE- Acoustimax
Kaisser Instruments- Priapos
ElectroniX Submarine- Preamp Pedal
Fuzzrocious- BDPG
HBE- Hematoma Bass Pre/Driver

 

If you like some aspects of that behringer why not try the pedal it's a copy of? Sans amp work great, especially for rock and metal tones. I have a sans amp RBI and love it. People can hate on them all they want but if they were junk you wouldn't have guys like Geddy lee from Rush all the way to Danny Kenny from suicide silence using them.

 

Personally, I found the MXR Bass Preamp to do exactly as you're describing. With controls set flat, it still just seemed to enhance the signal, and all the gain is transparent. With pre and post gain controls I'm sure you could match the active signal of your other basses, and the parametric EQ will boost those low mids for you

 

I use an aguilar tone hammer pedal for balancing a passive or piezo channel and love it. I use the other channel in an aby switch for an active 5.

 

Lots of good "clean" outboard preamps. MXR, Xotic, Sadowsky, the discontinued Alleva-Coppolo or 3Leaf Ensbler Etc

But another option is the Source Audio Programmable EQ.

Source Audio Programmable EQ

You can tweak the sound, match the gain levels and have a different preset for four different basses.

 

The Darkglass b7k ultra is very transparent without the distortion switch on. It's literally just EQ. Really good EQ though

 

The older Sansamp Acoustic DI works great, if you can find one.

 

Why not just turn the volume of the active bass down to match the passive bass? No additional gear required.

 

GK Plex

 

Sounds to me like the op just needs a switchable buffer for his.passive instruments, possibly with a gain control. A full on preamp might be overkill?

There are lots of simple, minimaly coloring buffers available. I've used this one & can vouch for its quality:
LEHLE

 

If you're looking for a straight preamp that doesn't color your sound and works for everything, maybe a Headway EDB-2 ? If you're looking for the ampeg tone, you could use one of their PF-20T or PF-50T as a preamp and/or DI without connecting a speaker load, connecting the transformer balanced line out to a power amp effects return (which is what I'd like to do).

 

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