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A thought on humming piezo pick-ups

Posted by Douglas Eric Marsalis on June 8, 2010 at 2:52am in Building Secrets, Tips, Advice, Discussion
I have seen over the weeks, since starting this beautiful addiction of building CBGs, many questions on humming problems on piezos.  I have been experimenting, researching and trying to find some answers to these questions.

I found this video --> https://www.youtube.com/watch?v=aJ3wLGanuCw <-- on YOu Tube on how the piezo will bend when electricity is applied to it. 

So I was thinking, is it possible that this is the cause of the humming that so many are finding?  Is it possible that by stopping the natural bend of the piezo that it causes a hum that we are all hearing?

OR will there always be a small hum no matter what is done?  Should the amp GAIN always be set to zero or should the GAIN be allowed to be set at anything (humming changes with different settings)?

I agree that wiring is important, such as if the wires touch incorrect spots on the piezo (red wire touches the metal OR the black wire touches the white ceramic area).  BUT I think the way many (including myself) not allowing the piezo to bend naturally may be causing some of this humming problem we are having.

See what I am talking about while the piezo is hooked-up to an amp.  Does it hum when you touch the wires, or hum more or less when you keep the piezo from bending (sandwiching it in between hard or soft materials)?

Those of you that read this, please share what you have used in mounting, wiring, or sandwiching your piezos.  If you have used hard materials in sandwiching, does the piezo have the space to bend?  Did you use a silicone type glue that may allow for bending or did you use a glue that is hard when it dried?

I hope that for those of you that have found great remedies will share your videos with diagrams for the ones that are still suffering through this.  Yes, I know that there are many videos out there, but this is an issue that seems to keep popping up every week on the website.

I would be interested in hearing your opinions on this.  Thanks.

Douglas

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Replies

  • Steve Graham June 16, 2010 at 9:30pm
    This is all really great everyone - thank you and I will also look to do some step by step stuff as I build the second guitar. All these comments give me the confidence to move forward. I will also try to embrace "failure" as a tool for learning. Thanks!

    Douglas Eric Marsalis said:
    Steve. You will find many ways to mount these piezos. I have played around with many different ways to mount them. For example:
    1. Embedding the piezo behind the bridge and placed inside a hole that I cut in the neck that goes through the box. The piezo was sandwiched between two furniture pads.
    Result---> worked OK.
    2. Sandwiching the piezo between two furniture pads and hot gluing to the lid next to and a little behind the bridge OR next to the low string.
    Result---> worked great.
    3. Sandwiching the piezo in a piece of foam and placing it right behind the bridge on the neck inside the box. The weight of the lid holds the piezo in place. No glue was used.
    Result---> worked great.

    DO a little search in the PICS area of this site (go to search and type in piezo). You will see a lot of photos of piezo mounts with some discriptions. This might help you in finding the best placement and mount.

    To make sure I have answered your question, You can use the tape only, but if you want to make sure it does not come off so easily, you can use a little glue too. If the tape is strong, you probably won`t need the glue.

    A few other things I have found:
    1. Make sure that there are no wires that are exposed (needs to be covered by either the plactic sheath or by soulder). I have found that any exposure will cause humming. Placing my fingers on the exposed wire stops it.
    2. Just a simple piece of foam works to dampen unwanted sounds.
    3. You can use hot glue to mount, tape, cylicone glue, ANYTHING really. Just use something that you can correct if you make a mistake.
    4. Make sure the black wire does not touch the ceramic area of the piezo AND make sure the red wire does not touch the metal disc. That goes for your soldering too.
    5. I hear that shielded wire is BEST.
    6. Make sure when you mount not to glue the ceramic side of the piezo to the lid. Glue the metal to the lid.

    If anyone disagrees with what I have written, please let me know. OR if you would like to add something, that would be great. I would love to hear from the MASTERS on what exactly they do. I would also love to see someone do a step by step with pictures of different ways to do these piezos and place it in the download area along with the building a CBG downloads. Perhaps when I get a little better with all of this, I will do it. I think that piezos are the number one problem that everyone has when building these CBGs for the first time. Hopefully we can all find the best solution.

    Thanks
    Douglas





    Steve Graham said:
    Hey there - I am at the piezo mounting stage on my first. I'm a little confused on the use of both mounting tape and hot glue. Is this correct, that with the lid open (exposing the inside of the box), you taped the piezos to the underside of the lid directly beneath each end of your bridge? And then why add hot glue if the tape is already securing the piezo to the lid?
  • Douglas Eric Marsalis June 16, 2010 at 8:15pm
    Steve. You will find many ways to mount these piezos. I have played around with many different ways to mount them. For example:
    1. Embedding the piezo behind the bridge and placed inside a hole that I cut in the neck that goes through the box. The piezo was sandwiched between two furniture pads.
    Result---> worked OK.
    2. Sandwiching the piezo between two furniture pads and hot gluing to the lid next to and a little behind the bridge OR next to the low string.
    Result---> worked great.
    3. Sandwiching the piezo in a piece of foam and placing it right behind the bridge on the neck inside the box. The weight of the lid holds the piezo in place. No glue was used.
    Result---> worked great.

    DO a little search in the PICS area of this site (go to search and type in piezo). You will see a lot of photos of piezo mounts with some discriptions. This might help you in finding the best placement and mount.

    To make sure I have answered your question, You can use the tape only, but if you want to make sure it does not come off so easily, you can use a little glue too. If the tape is strong, you probably won`t need the glue.

    A few other things I have found:
    1. Make sure that there are no wires that are exposed (needs to be covered by either the plactic sheath or by soulder). I have found that any exposure will cause humming. Placing my fingers on the exposed wire stops it.
    2. Just a simple piece of foam works to dampen unwanted sounds.
    3. You can use hot glue to mount, tape, cylicone glue, ANYTHING really. Just use something that you can correct if you make a mistake.
    4. Make sure the black wire does not touch the ceramic area of the piezo AND make sure the red wire does not touch the metal disc. That goes for your soldering too.
    5. I hear that shielded wire is BEST.
    6. Make sure when you mount not to glue the ceramic side of the piezo to the lid. Glue the metal to the lid.

    If anyone disagrees with what I have written, please let me know. OR if you would like to add something, that would be great. I would love to hear from the MASTERS on what exactly they do. I would also love to see someone do a step by step with pictures of different ways to do these piezos and place it in the download area along with the building a CBG downloads. Perhaps when I get a little better with all of this, I will do it. I think that piezos are the number one problem that everyone has when building these CBGs for the first time. Hopefully we can all find the best solution.

    Thanks
    Douglas





    Steve Graham said:
    Hey there - I am at the piezo mounting stage on my first. I'm a little confused on the use of both mounting tape and hot glue. Is this correct, that with the lid open (exposing the inside of the box), you taped the piezos to the underside of the lid directly beneath each end of your bridge? And then why add hot glue if the tape is already securing the piezo to the lid?
  • BenBob June 16, 2010 at 7:23pm
    Some people find that the piezo can be too sensitive if adhered directly to the top. It picks up clothing noise, etc. I've had that experience too, so the foam helps deaden the overactive high end a little. I added some hot glue to the back just for mass - to absorb vibrations a bit more.

    I haven't tried foam without backing - it might be great. Manufacturers of these kinds of transducers put some extra mass behind the disk, so I just copied that.
  • MichaelS Country Boy Guitars June 16, 2010 at 6:28pm
    I stuck mine on the back of the lid also and used a thin double stick mounting tape. This tape has no foam on it, juts a thin sticky film so it is stuck directly to the wood lid. I put some foam tape on the back of the piezo for echo canceling. It seems to work well, sounds good to me anyway.
  • Steve Graham June 16, 2010 at 5:57pm
    Hey there - I am at the piezo mounting stage on my first. I'm a little confused on the use of both mounting tape and hot glue. Is this correct, that with the lid open (exposing the inside of the box), you taped the piezos to the underside of the lid directly beneath each end of your bridge? And then why add hot glue if the tape is already securing the piezo to the lid?
  • BenBob June 8, 2010 at 12:43pm
    I've only done one, but I'm very happy with the result - rich tone and no extra noise or buzzing. I get good gain before feedback too.

    I used 2 radio shack buzzer elements and wired them in parallel straight to a jack. Then, I then stuck them to the inside of the top under each end of the bolt bridge. I used 3m heavy-duty foam mounting tape an then squirted a little puddle of hot glue on top of each one.
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