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How to measure pickup output?

Discussion in 'Luthier's Corner' started by mcdeath, Nov 12, 2004.


  1. Hi.

    I'm doing some work with producing custom pickups, more for my own satisfaction than anything else, but I've now come to an impasse of sorts. What I want to do is ensure a bit of quality control on my work. I want to be able to compare the pickups I produce with other pickups and ensure consistency and proper documentation.

    Is an oscilloscope the preferred tool for this?

    Thanks in advance!

    ed
     
  2. FerroFluid or Magnetic Viewing Film.

    Hmmm. Maybe if I shot a video of a custom pickup with a slow increase of the volume? Or mount it on a bass and then pluck the strings under the film or the fluid?

    Definitely wins the "wierd as hell" award. :)

    ed
     
  3. A9X

    A9X

    Dec 27, 2003
    Sinny, Oztraya
    An O'scope will work, but a soundcard is just fine and you probably have one that you can use now, free.

    If it were me doing this, then what I'd do is;
    - build a rig to test, then build something that will allow you to be consistent in your methodology wrt the testing electronics. For example, buy an old bass and rout a channel right through the body where the pups will fit and a plate that can fit the pup and mount it in a 'normal' position in the bass so you can quickly fit the pup for testing and positioning, depth etc will be consistent from sample to sample.
    - then devise some way of striking the strings mechanically so that the 'pluck' is consistent in testing. Doesn't need to be fancy.
    - then build a buffer for the pickup so that it interfaces well with the lowish, circa 10k input impedance of most soundcards, and has a gain so that you can get near full signal (0dBFSD) on the soundcard. When built make sure the rig has no noise/hum issues.
    - When you have your proto pup(s) finalised, record the output on the soundcard, string at a time using a sound recording and manipulation program. There are inexpensive versions. It doesn't need to be lab-spec, just workable and consistent.
    When you've recorded some .wavs of the proto pups, and measured their specs for R, L and C store the data and use it as reference.
    - Test your production pups. Compare the spectrums of the production and proto pups to see if they're close enough. If your test guitar rig is still able to be played, play the pups through an amp and see if they sound close to your ears. Keep your listening rig the same at all times. Again doesn't need to be fancy, maybe a decent headphone amp and some cans.
    - decide on the layout of your customer documentation and print up the results. Ship pup.

    All of this will take a bit of futzing around to set up, and decide what the allowable production variation can be, but should be cheap and easy enough to do and so long as it's consistent, will also let you know more clearly what you're doing as you prototype other designs. Absolutes in testing etc aren't really important, just consistency in the methodology and you'll learn a lot about what you're doing. Sound and sound quality is a nebulous thing to describe, but you don't need to describe it to anyone else, just understand how the measured and audible correlate.

    When you get the rig done, please also test other 'brand name' pups and publish the results. Along with tests like luknfur's 'Dimento' series' it would be very enlightening.
     
  4. Thank you.

    I was thinking of setting up a rig as you described it. I'm still working out the mechanics of the string plucking. I think I'm probably going to go with some sort of spring loaded device. Either that or I'm going to go and use a Legos Mindstorm kit and do a robotic version. :)

    Good idea about the soundcard. I was thinking about doing that but I also wanted to cover any other aspects and I wasn't sure if a soundcard would do all that.

    Thanks again!

    ed