Using a DI to Impedance match???

Discussion in 'Amps, Mics & Pickups [DB]' started by jazzbassnerd, Apr 8, 2004.

  1. jazzbassnerd


    Aug 26, 2002
    Would using a underwood-like high impedance pickup into a DI with an XLR to 1/4 inch cable into an amp effectively match impedance to make a pickup sound better, or have I completely miscalculated how DIs work? I dont know how i thought of this, maybe trying to find the least expensive way to impedance match a pickup to an amp? Thanks!

  2. McBass


    Mar 31, 2004
    Brooklyn, NY
    I could be wrong, but I think that the xlr signal coming out of the di will be a low z signal like for a microphone which isn't what you'd want. I know some amps like acoustic image have impedance matching inputs. Rather than a DI, maybe try a pre-amp that has an impedance correcting function. Sorry, can't think of any brands.
  3. Bob Gollihur

    Bob Gollihur

    Mar 22, 2000
    New Joisey Shore
    Big Cheese Emeritus: Gollihur Music
    DIs are designed to convert a relatively high unbalanced impedance signal to a balanced low impedance signal, primarily for its better resistance to noise and ability to withstand longer cable runs to a mixing board. DIs vary in input impedance, some are 1 megohm (suited for a piezo transducer) but many are lower, you'd have to check specs. But it would be useful only if your amp has a low impedance (150-600 ohm neighborhood) XLR mic input.
  4. jazzbassnerd


    Aug 26, 2002
    Thank you guys. The too low impedance idea was a worry of mine. Thanks for the help. I'm saving for the new acoustic image for when it comes out and I was looking for a cheap temporary fix. Thanks again.

  5. dvmweb


    Apr 20, 2002
    Atlanta MI 49709
    I do sound. This is what we do for URB, acoustic electric guitar, electric violin, etc.

    If you are going direct with your URB go Pick up to pre amp to DI Box and then xlr cable to board/snake. If your amp has an XLR out you would not need to have a DI box if your amp has an XLR out. If your amp has 1/4" out you should use a direct box.

    The XLR cable is the best way to go on long runs because you won't have as much noise as you would with a long 1/4" cable.

    You should spend the time to hook up what sounds best to you anyway.

    Walt MI/US :cool:
  6. lermgalieu

    lermgalieu Supporting Member

    Apr 27, 2000
    Palo Alto, CA
    He's trying to get to an amp, not a board.
  7. dvmweb


    Apr 20, 2002
    Atlanta MI 49709
    DI Box : Usually used to change Hi Z (Piezo Pick up) to Lo Z (XLR cable)

    Pre amp: Change impedance from pick up to amp. Also increase low powered signal.

    He asked about how to use a DI box. I explained how a DI is used. And how to go to the amp. But, thank you for your "comment" meester L.

    Walt MI/US
  8. basstuhd


    Apr 9, 2004
    Try this link.

    It's a preamp/blender that has a 10megohm input, which should be high enough for any pickup you throw at it. Its ouput impedance is 100 ohms which is probably suitable for your current amp. Many preamps like this and other brands accept high impedance signals for just the same reason your looking for one. Depending on the clarity of your current amp, a good preamp/eq may eliminate the need for you to buy a new amp.
  9. metron

    metron Fluffy does not agree

    Sep 12, 2003
    Lakewood Colorado
    You are correct. The low output impedance from the DI is what you want. Impedance matching is sort of a misnomer because it doesnt mean that the impedance needs to be the same. It means the source impedance (pickup) needs to be lower than the input of your amp.

    Many DIs have a 1/4 out as well as an XLR. This is designed to run into an amp although a converter would be adequate (but not ideal) if all the DI has is XLR output. Take a look at the Countryman Type 85 DI which I use frequently. When I used an amp with a lower input impedance (lower than 1 Mohm) the sound of my underwood was bad direct into the amp. I used the 1/4 out of the DI to run into the amp and that solved the problem. Now I use the Raven PMB II and it serves exactly the same purpose because its input impedance is the same as the Countryman. The Acoustic Image amps have sufficiently high input impedance such that a DI is not needed between pickup and amp. Most bass amps are not designed this way and do need a DI in between to achieve best sound with a piezo pickup like the underwood.