Piezos, Passive volume & the NS-Design NXT

Discussion in 'Pickups & Electronics [BG]' started by kumimajava, Feb 7, 2021.

  1. kumimajava


    May 19, 2010
    Tokyo, Japan
    I'm considering adding some piezos to a few of my (fretless) basses, and have been reading up on the related electronics. Especially, I've been curious regarding the "passive volume/tone adjustment" on piezos.

    Yes, I have used the search function, and read many of our threads on this. The consensus seems to be: don't passively adjust volume/tone on piezos before buffer - it will lead to noise/tone-suck/low-end-loss, etc.

    Accepted wisdom seems to be "buffer first, adjust later."

    Equally, many of players who have used the (passive) NS-Desiogn NXT EUBs or "Omnis", say that they sound best with a preamp with a 10meg input impedance.

    However - the NXT has BOTH a passive volume, and tone (both 1meg pots), and from my own experimentation, there seems to be no significant degradation in sound quality from adjusting these on-board on the passive instrument, rather than in the pre-amp. The NXT seems to be just fine - no noise/low-end-loss etc from adjusting the on-board passive controls, if it then goes to a dedicated piezo-pre.

    This leaves me very confused. How come the widespread caution against passvie volume/tone adjustment on piezos, while the NXT seems to handle them just fine?

    I've attached the NXT wiring diagram below, in case it would of help to anyone willing to explain :)

    dbassnut likes this.
  2. equill


    Nov 25, 2010
    As long as it's connected to a high-impedance buffer, the volume and tone controls work fine for me.
    I'm guessing that advice comes from what happens when you plug piezos into a lower-impedance preamp: rolling off either control makes it sound even worse.

    How are you planning to retrofit the pickups, electrically/electronically? With an onboard buffer/preamp on each instrument, or all passive into an outboard preamp?
  3. dbassnut


    Apr 1, 2008
    Was it easy to take apart? I heard that the piezo can get misaligned with bridge and cause a volume drop. I'm planning on taking apart my NXT to check. Any advice? Thanks
  4. kumimajava


    May 19, 2010
    Tokyo, Japan
    I've not had piezo misalignment issues, and the only time the bridge came loose was when I was changing strings (for some reason I loosened too many strings at the same time, and there wasn't enough pressure to keep the bridge down).

    Overall, the NXT is very tidily put together, and it's easy to see what the electronics are doing. If you're wanting to check bridge/piezo alignment, it may be enough to just loosen the string tension & lift out the bridge. From what I understand, it's only kept in place by the string pressure, and no other adheisive.

    Hope that helps - let me know how it went, or if you have any other questions :)
  5. dbassnut


    Apr 1, 2008
    Thank you. I'll try loosening the strings & re-seating the bridge. Maybe raise the bridge height a little again. :). Is there a maximum string height on the NXT bridges? I'm worried that it is possible to over raise the height of the bridge until the screw threads inside come loose.
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