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is a passive mixer possible?

Discussion in 'Amps, Mics & Pickups [DB]' started by CB3000, Jan 5, 2007.

  1. CB3000

    CB3000 Supporting Member

    hey tech-minded people,
    would i be able to make a simple passive mixer to blend 2 pickups? say an underwood and a FC? just something to mix them before they hit the amp? either a PAN pot or just two volumes. what would the pot values/tapers need to be?

    (BTW I have tried all the Mixer Preamps out there)
  2. What didn't you like in them?
    Having good results with passive components impossible to me, furthermore when you take into account that a very high impedance has to be "seen" by the piezo devices.
  3. robgrow

    robgrow Supporting Member

    May 1, 2004
    Cincinnati, Ohio
    If I'm not mistaken, Eric Roy used a passive mixer circuit in the original incarnation of what is now the Revolution Solo pickup (which had two elements). Maybe he'll jump in here. As I recall it was a very simple circuit. Anyway, it is possible to build a passive mixer. Whether you will like it or not is another matter, but it would be so cheap to build it would probably be worth experimenting with.
  4. willem1


    Jan 8, 2007
    You may want to consider another option. There are some really nice half and third rack pres out there. If you get a stereo pre, then you can dedicate one channel to each pickup. If the pres have inserts, that would also allow you to insert compression or related dynamics into the signal chain. If your bass amp has only one channel in, then use a "y" cable to drop the two stereo channels into the bassamp. You'd need to take some care in the gain staging, but it shouldn't be all that tough to balance it.

    One solution that comes to mind are 1/3 rack units made by FMR audio. There are others, too; Summit makes a mono 1/2 rack, but you'd need to buy them in pairs. As for full rack mounts, a pair of Chandler Germanium pre/DI units would be killer in the application you describe. So would a pair of Avalon U-5s.

    As for the FMRs (no this is not a commercial) they offer a unique fit as a system for the use you're inquiring about. The stereo preamp has inserts <http://www.fmraudio.com/RNP8380.htm> for their two compressors they offer; the RNC is a really clean and transparent compressor <http://www.fmraudio.com/RNC1773.HTM> and the RNLA is a darker and more colored sounding leveling amplifier <http://www.fmraudio.com/RNLA7239.htm>. This would offer a robust set of sonic options for your bass pickup feeds.

    I've used the RNC and RNLA in my studio work and in some live situations. I've not used their stereo pre, but the FMR folks do first class work. It just seemed a natural for the question you asked, whether or not you're interested in adding compression, outboard EQ or other dynamics to your current bass rig.
  5. willem1


    Jan 8, 2007
    Forgot to add...

    1) If you want to build you own stereo preamp or have someone professionally mod your existing bassrig for two quality pre channels, check out these pres at 7th Circle:


    2) If you want excellent stereo pres with A/D conversion for recording direct to digital, check out the API A2D:


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