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Thread: Piezo Pickup Build Notes and double sided tape Question

  1. #1
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    Default Piezo Pickup Build Notes and double sided tape Question

    A while back while researching mandolin pickups, I realized that it was well within my education and abilities to build my own. I don't claim to be The expert in any aspect of mandolins or their sound, but I'd like to share my experiences with this project.

    Version 1.0
    Single piezo disk externally mounted with sticky Tak. Good crisp sound, but inadequate shielding on leads. Humm unacceptable.

    Version 2.0
    Dual disk. I made three prototypes, the first one, Y cabled, was the best sounding.
    A couple things I learned:
    Supple, well sized and properly shielded leads are required.
    Soldering piezo disks is an art. I was hit and miss on getting it right, so I chose to avoid perfecting this art by using disks that came with pre-soldered leads. Shorten the piezo leads to 1/2" and solder to your "well sized and properly shielded leads".

    Mounting the disks. I can't say enough how good sticky Tak is for surface mount. It's quite dense and easy to work with. Change pickup locations at will. Experiment with Tak thickness.

    The geek in me wanted to see what I was hearing so I ran a discrete lead to each disk and recorded separately along with a reference track via external mic.
    Differences between locations were very apparent on a spectrum analyzer. It was interesting, but ultimately trust your ears. Signal levels, frequency response are just interesting details along the way to getting your sound right.
    In my setup, the preamp was also essential to a full sound. Frequency response tailed off noticeably without it. I use a Schatten Mini Pre.

    I took my two piezo Y cabled rig to a couple gigs and was pleased with how well it stood up to the band.

    Version 3.0
    Next, I decided to mount the pickups internal and get them out of site. Well my MK is not an expensive instrument by any means, but I really had to steel my nerves to tear it down and drill out the end pin hole for the jack. Baby steps. Slow and steady is the way to drill an instrument.
    A bit more experimentation on location with Tak and I settled in on the F hole side under each bridge foot, slightly towards the tail. Double sided tape for the permanent mount.
    Now here's where things went awry. At gig volume, the sound was harsh. I was also hearing piezo quack on the open A string. After a period of misdirection investigating impedance matching, filters and eq, I read the cafe forums and found an answer. I added a second layer of double sided tape to each disk mount. Wow, quack fixed. Thank you forums.
    Also full coverage of tape on the disk sounds richer than partial coverage.
    I also tried thin foam tape. The sound was muddy, akin to a poor mic.
    I was well on my way to playing happily ever after until that fateful August day when my mandolin got some sun. Lead fit wasn't great on one pickup and it stressed the warm tape. The tape let go at a gig. Clank rattle clank, sigh.... I had to re-stick it with my pinky while on stage and check it after every song. It didn't survive the gig. Two lessons learned.
    1) Keep to the shade.
    2) Sizing the leads can't be done well until you determine exactly where you will mount the disks.

    Version 3.1
    I removed the pickup and recently rebuilt it. Fine tuned my lead fit, shielding and end pin jack mount. Attached the disks with two layers of double sided tape. Sounds great. Best ever. Gigged it twice last weekend.

    So my question for those of you that use double sided tape on pickups or elsewhere; What brand/type of tape holds up best?

    Steve

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  3. #2
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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Steve,

    For most things requiring double sided tape I have always used carpet tape with very rare failures regardless of what was being stuck together....no specific brand. I have heard some great things about 3M VHB double sided tape but have not found need for it yet.

    Good luck with the pickup!
    Tony

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    Registered User almeriastrings's Avatar
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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    One thing worth mentioning is that the diameter of the disc has a big impact, i.e, a 10mm disc vs. a 20mm disc. The resonant frequency is different, so is the output voltage (the 20mm can produce really big 'spikes'). For most purposes (except string bass) the smaller disks seem to perform best...

    I did pretty much exactly what you described here when I fitted up 20 (!!) ukes recently on a tight budget. I also tested the result on a Gibson F5 and a Martin D-18.

    Here's a disc ready for use:


    Click image for larger version. 

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    If the instrument top gets hot, tape (all kinds) can fail. So can some of the 'putty' type adhesives, though the super sticky black stuff AKG supply for use with the C411 seems to hold up well... I ended up super-gluing them on with gel adhesive. Perfect (these were all internal installs) output via endpin jack and a Tapastring Vintage jack in one instance.

    Much of the 'quack' is from over driving the preamp input stages. The double thick tape acts as a physical attenuator... however, if you use lower sensitivity smaller discs, this is not normally necessary.

    Sound: I fit "well known" but 'similar' pickups frequently.... they cost quite a tidy sum each. These cost all of 15 cents each. I thought they sounded just as good.....
    Gibson F5 'Harvey' Fern, Gibson F5 'Derrington' Fern
    Distressed Silverangel F 'Esmerelda' aka 'Maxx'
    Northfield Big Mon #127
    Ellis F5 Special #288
    '39 & '45 D-18's, 1950 D-28.

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    I used two layers of tape, but super glued them in place so they won't let loose. They still provide the buffer and sound good, but after several years of gigging, some on a riverboat in a humid environment, they are still working perfectly. I get compliments often on the sound of my mandolin. The mandolin sounds good acoustically and that makes a difference too. The better sounding instrument the better sounding pickup.

    yes super glue gel always
    Last edited by pops1; Dec-04-2017 at 10:50pm.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Thanks for feedback.

    Quote Originally Posted by almeriastrings View Post
    For most purposes (except string bass) the smaller disks seem to perform best...
    I ended up super-gluing them on with gel adhesive.
    Good detail on disk size. I did start with three sizes; 10, 15 and 20. My ear quickly settled on the 10s and I never gave the larger ones a fair chance. Glad to know that was the right call.
    I'll have to check out super-glue gel adhesive. I read forum comments about using super glue, but it seemed unsuitable since the super glue that I know is ultra thin. I missed the gel detail, which probably makes all the difference.

    Steve

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    It is interesting that the K&K pickups for mandolin are larger than any other pickups they sell. They are also thicker so I am wondering if thickness plays a part in all of this. I have used smaller discs, but the best sound I have found is the larger K&K. When I talked to them I was told these are specifically for mandolin and the thickness helps with the brightness of the mandolin. Is it an option to get the smaller discs you are talking about thicker?
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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    We can safely say that 'leading brands' coat the tops of the discs in epoxy potting compound....

    The discs are certainly not 'made for mandolin'. They are made as general purpose sensors. All of these things are produced in vast numbers for the consumer electronics market from a limited number of factories in China, Korea and Japan. They then get repackaged and 'branded'....

    Here's a 'well-known brand' being installed. I carefully tested the discs being used....

    Click image for larger version. 

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    Gibson F5 'Harvey' Fern, Gibson F5 'Derrington' Fern
    Distressed Silverangel F 'Esmerelda' aka 'Maxx'
    Northfield Big Mon #127
    Ellis F5 Special #288
    '39 & '45 D-18's, 1950 D-28.

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    By being made for mandolin the R&D part of K&K was working on a pickup that would sound good in a mandolin for some time. We communicated over a period of a year or more. What they came up with is a heavier, larger disc, it is only used in mandolin. That is what I meant by "made for mandolin". This is what I was told by Deiter at K&K. At the time I was doing a lot of experimenting on amplifying my mandolin and installed and removed at least 20 different sets of the smaller discs in different ways of mounting. Some were close in quality of sound, but the larger disc is a much better sounding pickup than all the small ones I tried.
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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    As someone famously once said "Well, he would say that, woudn't he?"...

    Do I buy it? In a word: No.

    That is just my opinion, though. Feel free to disregard.
    Gibson F5 'Harvey' Fern, Gibson F5 'Derrington' Fern
    Distressed Silverangel F 'Esmerelda' aka 'Maxx'
    Northfield Big Mon #127
    Ellis F5 Special #288
    '39 & '45 D-18's, 1950 D-28.

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Quote Originally Posted by almeriastrings View Post
    As someone famously once said "Well, he would say that, woudn't he?"...

    Do I buy it? In a word: No.

    That is just my opinion, though. Feel free to disregard.
    I don't have to take his word, I have both in the shop. I looked at just the brass disc from the side and the mandolin pickup is easily 3 times thicker than the small disc. I am only looking at brass disc, not anything else that may be glued on for advertising. I was originally going to measure, but not wanting to remove anything from the pickups since visually it was easy to see the difference in the thickness of the two.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    No comment.
    Gibson F5 'Harvey' Fern, Gibson F5 'Derrington' Fern
    Distressed Silverangel F 'Esmerelda' aka 'Maxx'
    Northfield Big Mon #127
    Ellis F5 Special #288
    '39 & '45 D-18's, 1950 D-28.

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Quote Originally Posted by almeriastrings View Post
    No comment.
    That is too bad, I always look forward to you posts as they are informative and knowledgeable.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Gibson F5 'Harvey' Fern, Gibson F5 'Derrington' Fern
    Distressed Silverangel F 'Esmerelda' aka 'Maxx'
    Northfield Big Mon #127
    Ellis F5 Special #288
    '39 & '45 D-18's, 1950 D-28.

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Interesting to hear about the disk thickness. I could only guess that this translates to more mass.
    I used generic disks, they're pretty much wafer thin. I did put a dab of silicone rubber on the disk where the leads attach to secure the wires so that wire movement or vibration would not stress the solder connections.

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Quote Originally Posted by almeriastrings View Post
    Shows a thickness from 2-8mm, quite a difference. I believe it is possible that in certain circumstances a thicker disc might be advantageous.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Still none of the K&K pickups come even close to 2mm, unless you include the covering, and even then. Let alone 8mm.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    My apologies, I looked at the first column, which was rings. Discs went from .3mm to 1mm.
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  23. #18
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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    When I was experimenting a lot with piezo discs I found that the only way to eliminate induced hum was to shield the sensor side of the disc, too. I cut brass to shape and soldered it to a bit of the shield which I un-braided to use for this purpose. I then covered the active side of the disc with black epoxy and sat the extra shield disc into the top surface, being careful to not let it short to any part of the "hot" wire or solder connection.

    This made a nice sandwich transducer to affix by gel CA, as per K&K method.

    As to size, you can cut the larger discs with scissors to make smaller pieces. If you cut carefully and file the edge to ensure no shorted material it works perfectly.
    rudy44

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    for the very most part, the better the contact of the acoustic piezo elements to the sound board, the better the transfer of both tone and output. this means using super glue and not d/s tape or some tacky form of goo. yes, once done, the transducers will be destroyed if removal is attempted. such is life. i use jjb prestige transducers for my mandos with quite good results. as with any piezo, placement is rather important.
    Proud owner of a custom cigar box 4 course mandolin!

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Some observations:

    1. I had a K&K Twin installed in my Breedlove American a couple years ago. The 2 sided sticky tape failed on the treble disk at a gig. I had a luthier re-glue it with CA gel. To my ear, the CA gel side sounds better. I would like to have the bass side removed and re-glued, but I was told that its dangerous to try to remove the taped disk as it could damage it. I kind of wish that the tape would fail so I could re-glue it.

    2.They make a tapered hand reamer for end pin holes that is much safer to use than a regular drill.

    3. I've tried a some other name-brand piezo pups and none sounded as good as the K&K. All of the others I tried were applied with sticky tack putty. I'm not a fan of the sticky putty because they creep (move) around on the top, sound muddy, have a tendency to release, and they leave a residue.
    Never say "bouzouki" to a TSA agent...

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    I have successfully removed dozens of K&K pickups when I was experimenting with placement and size. I like them glued in too, but I still use the tape, two layers. Sounds really good, and has not failed in several years including weekly hot humid gigs on a boat on Mississippi.
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  28. #22
    Mike Story
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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Hello pops1. When you talk about glue and double sided tape, where are you putting the glue? Between the two pieces of tape, between the tape and the mandolin, between the disk and the tape? Also, what kind of tape are you using? Thanks.

    Mike

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    I am not using special double sided tape, I am using two pieces of the tape supplied with the K&K. That is a thin double sided tape, so any thin double sided tape will do if you don't have that. I glue the tape to the disc, glue the tape to the tape, glue the tape to the mandolin. Use the gel super glue, they used to provide it, but don't anymore. I have had problems with some and have gone to Gorilla super glue. It is a larger container, but not much glue, you have to shake it to mix and it last a long time as opposed to other super glues.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

  30. #24

    Default Re: Piezo Pickup Build Notes and double sided tape Question

    Has anyone tried using hide glue to affix piezo elements to the top of a mandolin? It seems the reason you'd want putty is to prevent damage to the instrument if you should ever decide to remove the pickup, though it comes at a sonic cost. Might hide glue offer the tonal properties of superglue with the added benefit of being easily removed by a luthier?

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    Default Re: Piezo Pickup Build Notes and double sided tape Question

    I have removed piexo pickups glued with super glue dozens of times. If you take your time you can not damage the pickup. There is a some tearout on the top, but it is underneath and not a large problem.
    THE WORLD IS A BETTER PLACE JUST FOR YOUR SMILE!

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