Two piezos - single or two channel preamp

Discussion in 'Pickups & Electronics [BG]' started by tarbie, Jul 2, 2013.

  1. tarbie

    tarbie Guest

    Sep 13, 2012
    Hi all. I'm planning on putting two piezos in my current build - a 20 inch scale length plastic stringer, like the Kala electric ubass - with a blend pot and preamp. The piezos will be an undersaddle one and a disc in the neck pocket. Does anyone have any thoughts on whether I should put the blend pot after the amp and use a two channel preamp or if I should put the blend pot first and then just a single channel amp, or wouldn't it make a difference?
    For the sake of a bit of extra wiring I don't mind knocking up a two channel amp but I suppose it's got to be worth doing and I've only ever done piezo/magnetic combos so I've never considered it before.
    Any thoughts would be greatly appreciated.
  2. It's best to buffer them. Trying to blend them without buffering will result in variable impedance loading on the elements.
  3. walterw

    walterw Supportive Fender Commercial User

    Feb 20, 2009
    what the heck is the piezo in the neck pocket for? i've never heard of that one.
  4. Michael Manring's Hyperbasses have piezos in weird places on the neck, for his sound effects. I suppose you could do something like that, but I agree, the neck pocket is an odd place for a piezo element.
  5. tarbie

    tarbie Guest

    Sep 13, 2012
    The piezo in the neck pocket idea came about because I was initially going to just put one under saddle piezo and an internal guitar preamp in because bass ones seem really expensive (and at the time i didnt fancy making my own though i'm coming round to the idea more now). That got me thinking though that any tone controls probably wouldn't affect the right frequencies since the preamp is for a guitar.
    I've seen a few people mention putting piezos in the neck pocket, mostly on CBGs, and thought it might give me a warmer tone than the under saddle and I can blend the two to get a more effective tone control.
    Any thoughts?

  6. M0ses


    Sep 11, 2009
    Los Angeles
    Have you seen the Fdeck piezo pre? If you do some searching around here (or it might even be easier using Google) I'm quite certain you can come up with an extremely simple schematic designed by Francis Deck to build. And then I'd recommend an offboard EQ to go with it/them. He's an active member here and will probably be happy to answer more questions.
  7. ex-tension


    Jun 11, 2009
  8. tarbie

    tarbie Guest

    Sep 13, 2012
    Ok I suppose I'm getting to the crux of my problem...given that I'm building a 20" poly stringed bass and ready made bass preamps all seem expensive, what are people's thoughts about how I should set up the electrics?
    I can follow a schematic for a preamp (just about), I live in the UK so postage can be a problem from the US, and I want to get the best sound I can out of one or a combination of piezos on a budget.
    I'm just at he stage where I need to make sure I can fit whatever electrics I choose into the cavity I'm about to rout.
    Throw something interesting at me...

    Thanks very much for your thoughts so far, it really is helping.

  9. Steven Gaub

    Steven Gaub Guest

    Sep 8, 2007
    I have the U-Bass hard body and I have had no end of problems with the preamp. Replaced it and now it is dead again in less than a year. As you seem to have some technical knowledge and skill what are your ideas on the subject? What do you know of think of the LR Baggs and Mi-Si electronics used in the "California" U-Bass.