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Ukulele pickup noise.

  • 19-01-2011 9:18pm
    #1
    markok84
    Closed Accounts Posts: 857 ✭✭✭


    Hi,
    I recently bought a cheap uke from lidl (which sounds great with Aquila strings on it). I made my own pickup from 2 piezo transducers that I got from alarm clocks and a 1/4 inch jack chassis on the body.

    I also put a volume pot on the line so I could control the volume locally, and I put a .01mf capacitor on each of the transducers to reduce the tinny sound I was getting through my amp.

    Overall the result I'm getting through the amp is quite impressive for a homemade job, however there are some issues.

    I'm picking up extra noise from the cable when the volume on the uke is up to the last. As in if I touch or rub the cable you can hear it through the amp. Also when the vol pot is turned to anywhere between on fully or off completely a buzzing sound comes through which is eliminated if I grab the lead at the jack.

    This would lead me to think I have a bad ground somewhere but I just can't figure it out, I've tried rewiring every way I can think and the way I have it is the best solution. I've attached a little wiring diagram to show how I have it wired up apologies for how shít it looks, I'm not an electronic engineer. The yellow blobs are the .01mf capacitors.

    wiring_diag.jpg

    Some info on the components:

    This is the jack chassis I've used. I stupidly never checked where I was boring the hole for the jack and there happened to be a block behind the centre point on the body so I had to use this long reach chassis. (which is stereo) I'm only using one pole on it though.

    This is the potentiometer I used.

    Any help would be greatly appreciated.

    Thanks

    Mark


Comments

  • #2
    eoin5
    Registered Users, Registered Users 2 Posts: 2,141 ✭✭✭eoin5


    No expert here either but it sounds like there could be an impedance mismatch going on between the piezo and the amp, I'd imagine your pickup has a very high output impedance. You could try a DI box with a high input impedance tolerance or you could build a little FET preamp . Anything else I can think of would start to cost a bit.

    Other than that have you earthed the back of the pot? As for the lead I'd imagine its going to be fairly susceptible to any kind of movement due to the size of it and the type of pickup its got.


  • #3
    Ghost Buster
    Banned (with Prison Access) Posts: 5,172 ✭✭✭Ghost Buster


    Im just annoyed that I missed ukuleles in Lidl!!


  • #4
    markok84
    Closed Accounts Posts: 857 ✭✭✭markok84


    eoin5 wrote: »
    No expert here either but it sounds like there could be an impedance mismatch going on between the piezo and the amp, I'd imagine your pickup has a very high output impedance. You could try a DI box with a high input impedance tolerance or you could build a little FET preamp . Anything else I can think of would start to cost a bit.

    Other than that have you earthed the back of the pot? As for the lead I'd imagine its going to be fairly susceptible to any kind of movement due to the size of it and the type of pickup its got.

    Thanks for the post Eoin, very informative. I think you're right about the impedance of the buzzer, I noticed when I put a higher rated capacitor on the transducer a lot of the very high end noise was reduced but the transducer wasn't able to pick up anything from the strings then. I'm getting a loan of a DI box later on from a friend so I'll report back on that. I'm gonna try making one of those preamp's for my classical guitar though. I'm trying to figure out how to mount it discretely on the guitar first though.
    Ghost Buster wrote: »
    Im just annoyed that I missed ukuleles in Lidl!!

    I'm sure they'll get them back in again after skiing season & surfing season :pac: My uncle sells music instruments, he wasn't too happy with me buying stuff from lidl, but it was €20 I couldn't help myself!!!


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