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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