Piezo pre AND mag pre onboard using Y cable out?

Discussion in 'Pickups & Electronics [BG]' started by jibreel, Jan 1, 2015.

  1. jibreel


    Apr 12, 2005
    Searched but no luck.
    Rob Allen bass with Fishman Natural 1 piezo/preamp. This is the integral sound for this bass.
    I am adding a single Bartolini pickup and preamp.
    Can the two preamps be wired to a single output jack or would there be an impedance mismatch ?

    I know Fishman has a power chip blend pot but I wanted to see if this simpler way would work.
    I am happy to have two vol controls so do not need a blend pot specifically.

    Thanks for any advice !
  2. It's rarely an issue. It's done all the time on mixing consoles. Just throw a summing resistor in series with each output.
    jibreel likes this.
  3. Or blend them with an emg blend pot. Its just a 25K dual gang linear pot. No need for summing resistors here as the in-line resistance is in the pot when the signals are blended. (if you get what i mean.)

    It would be nice also, if you can adjust the gain of either of the preamps. Otherwise all the balancing you have is really just the pickup screws.
  4. jibreel


    Apr 12, 2005
    Thanks !!
  5. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    the simplest really would be to replace the matrix pre with the powerchip!

    it's designed to do just what you're looking for, right down to automatically splitting the sources with a stereo cable or summing them if you use a mono cable.
  6. gpx1200

    gpx1200 Supporting Member

    Apr 24, 2013
    spencer mass
    I saw a a board on the john east website for mixing in a piezo , it might be worth checking out, I have a u retro delux in one of my basses and its a killer pre
  7. jibreel


    Apr 12, 2005
    Thanks Walter !
  8. jibreel


    Apr 12, 2005
    I just tried an experiment. Two standard cables, one into the Rob Allen piezo bass and the other into my STR with Bart electronics. Connected the two cables to a 1/4" splitter at the amp input. Worked great !!!! Perfect sound. No hum. Am I missing something?

  9. Most opamp preamps have a series resistor on the output partly for this reason. If you like, try wiring an emg blend pot in a box with three jacks - two inputs and one output. And see if you get a smooth blend from one bass to the other.

    Notice that the tone controls in the bass on the right won't effect the signal from the piezo. If you are happy with it this way, then as I mentioned, when you get your fretless routed and fitted with the bart and pre, all you need is that blend pot.
  10. jibreel


    Apr 12, 2005
    Thanks ! Is there a reason why you suggest emg blend pot over other blend pots?
    I may not actually need a blend pot though. I am happy with vol / vol so I can blend with the individual vol pots from each pre.
  11. The difference between an EMG blend pot and any other blend pot is like, 17 dollars of difference and a little green board.
    If you want a blend pot, just get any dual gang pot with an appropriate resistance, like 25k or 50k.
  12. Several. Firstly a blend pot is usually MN or log/antilog, and for this you actually need linear, which is what the emg one is. Secondly, that little green board will make it easier for a novice to wire. Thirdly it has a centre click, which a regular linear pot won't have. Fourthly, I noticed your bass is rear routed, and this pot will have a longer than standard threaded portion. And fifthly, IME, they are good quality Alps pots.

    Cool. If you get a volume drop or anything weird with volume control interaction, then as line6man said, use a couple of summing resistors.
    Last edited: Jan 5, 2015
  13. Last edited: Jan 5, 2015
  14. jibreel


    Apr 12, 2005
    Thanks Robbie !
  15. Oh, and be prepared to change the phase of your magnetic pickup. It's hard to predict which way to wire it because of the way the bridge creates voltage when the strings are plucked, so I wire a temporary phase reverse switch to the signal from the magnetic pickup and when all the electronics are up and running, I wind the mag/piezo blend to the middle and flick the phase of the magnetic pickup back and forth to find the best sounding polarity.
    Last edited: Jan 6, 2015