Installing a K&K in OM - Question about location of endpin jack

Hey Octave Mandolin folks! I have a question that I figured someone here has run into before. I own a Black GBOM and want to install a K&K or JJB pickup in it. I have installed K&Ks in mandolins and guitars before, so I am ok with most of the mechanics of it.

My question is should I use the existing hole where the strap button end pin is located, or should I drill a new hole in the center of the side of the instrument (where I assume there is an end block)? I am going to try to attach a picture to show what I mean.

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I watched Sarah Jarosz on Austin City Limits, and it looks like her Clark GBOM has the pickup installed with a separate hole drilled in the center just for the pickup end pin jack.

Just curious if anyone else has done something similar. When I installed the K&Ks on regular mandolins, I used the strap button end pin hole and also reamed out the tailpiece to fit the jack in its place, but that is centered on the rear of the instrument.

Thanks in advance for your advice!

I installed an L R Baggs Anthem in my Eastman 'cello and used the existing endpin hole to run the jack through, and then attached a screw-in type strap button in place of one of the tailpiece mounting screws. (I eventually upgraded the strap button to a quick-release type strap button... Dunlop maybe?)

It would seem logical to drill a separate hole given the space available.

When I had a K&K fitted to my GBOM, also a Clark, I opted for a strap-pin jack. That involved enlarging the tailpiece hole and that was where the problem started (I’ve told this story before). Austin seems to use some particularly hard brass (bronze?) in his tailpieces which jammed in the pillar drill, the destroyed remnants of the tailpiece flew across the room and my luthier dissappeared to the bathroom to stem the bleeding. Austin kindly made me a new one.

If you do decide to drill out the tailpiece, make sure it’s fixed to something firm beforehand.

I have fitted three of my own builds (two mandos and an octave) with JJB twin pickups, and for all three I drilled a separate hole for the jack socket, placed about 4 o'clock on the treble side of the instrument (looking at it from the front). I fitted the pickups after I had built the instruments rather than during the build process, so I did not reinforce the side internally, but so far this has not been a problem.

I use an Allen tailpiece on all my OMs, and I prefer to drill a separate hole below the tailpiece for the K and K input. It's easier to get your hand inside to mount the assembly, and I also like to have the chord a bit lower than right there at the top protruding out. Customers seem to like this set up, and still use the button at the tailpiece for their strap. You can leave the strap on pluggin and unplugging.

However, for a guit zouk, I replace the strap button with the pick up input, since I use a fixed bridge for those.

Thank you to everyone for your insights and advice! I am still kind of on the fence about which way to go, but I think I am leaning toward a separate hole for the input jack. As Zookster said, it will move the instrument cord a little further away from the top of the instrument. This is an f hole GBOM, so I will have to use an old string to fish the jack through the hole regardless of where the hole is located. Not the most enjoyable install to do, but I would like the ability to plug in on occasion.

Again, I appreciate everyone's insights. I'll post an after picture when I get it completed.

This post from a while ago shows ways I've approached this.

I like the end pin jack / strap button through the tail piece. Unfortunatly most tailpieces are made for mandolin which puts it in the wrong place. I have made a few home made tail pieces that center the jack / strap button (when the instrument is deeper) . It is a pain and some may find it tacky. A sepreate hole in a convient spot is very acceptable to me.

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The endpin jack needs a 15/32" hole. I've put them in through cast tailpieces but I have a big drill press. I take the tailpiece off and temporarily screw it down to a big block of wood for the drilling with lubrication.

I would put the jack separately in the tailblock below the tailpiece. This way you can use a strap on the traditional endpin. If you're hesitant to add that extra hardware to your beautiful mando then I would consider getting the tapastring harness that goes in a traditional sized endpin. It does have an 1/8" jack so you'll need a converter chord to get back to 1/4".

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Originally Posted by Jake Biddix

Again, I appreciate everyone's insights. I'll post an after picture when I get it completed.

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I don’t have any insights to offer but would welcome more pictures of and information about your Black GBOM!

I didn't get around to doing it this past weekend, but plan on tackling this project this coming one. I ended up buying #42 (the answer to life, the universe, and everything else) directly from Mike here on the classifieds. I had him install a pickguard on it (see pictures), but looking back I wish I would have asked him to extend it all the way to the bridge. I thought about just hanging a clip on mic from the pickguard to the treble F hole, but I really haven't researched those lapel mics. So anyways, here are a few pics. Fantastic deep sounding OM with a whole bunch of sustain.
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My one Apple device (iPod) always uploads images to the Café the wrong way. If I save them to the PC first it usually fixes them. Fantastic looking instrument. Hopefully Allen or someone will start making an octave specific tailpiece. I do not put the 15/32 part of the jack through the tailpiece. I use the jacks step down (diameter change) to anchor the jack to the tailpiece. I also find 15/32 to be too tight for the tail block hole. I use a slimmed down 1/2 bit or 15/32 + some sanding. All of this points to the ease of a second hole.

I hope you join us in the Mike Black social group where you can find build photos of that GBOM in progress:

https://www.mandolincafe.com/forum/g...478&do=discuss

There’s also Mike’s audition of the instrument at completion:

the Tapastring vintage jack is 1/8" so will not need reaming out the tapered hole, as a 1/4" jack would ..
Only down side is 1/8" is not as robust as 1/4" and you would need an 1/8" male to 1/4" female patch cord adapter .
It, strain relief secured to the tailpiece ..

http://www.tapastring.com/vintagejack.htm

I think an 1/8 inch jack makes very good sense for a penetration through a thin side without a block inside. A delectate cord with an 1/8 inch is far less likely to damage the instrument if (heaven forbid) it gets dropped or jerked. You can get a cord that is 1/8 on one end and 1/4 on the other. I like the 1/8 end to be 90 degrees. My kids broke off all of my 1/8 male to 1/4 female adaptors. Now I only get that configuration as a cord from Parts Express or Mouser or make my own with their parts. Mouser also has piezo transducers. You can make your own pick up too. I have not come up with a homemade one that is good enough for mandolin.

Had some time yesterday to get this finished. Installed a JJB through the original endpin jack hole and tailpiece. I've done quite a few K&K or JJB installs, so it went really well. I was just a little concerned when I used the endpin jack reamer as the hole is not centered on the back. Thanks for the support and suggestions! I'll try to record something on it soon! That's the next dilemma! What songs do well on the octave?
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Originally Posted by Jake Biddix

I'll try to record something on it soon! That's the next dilemma! What songs do well on the octave?

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When you’re Sierra, the answer is anything:

i just realized that I put the strap screw on backwards, and of course I don't have enough thread left to install it the correct way...I'll have to adjust it this evening to get the strap screw on correctly. It kept on popping out the 1/4" jack, and I couldn't figure out why till I looked at one of my guitars!

Sierra can do anything! I was thinking more along the lines of Shady Grove capoed up to E or something! Maybe Girl from the North Country like Sam Bush does on mando.

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Originally Posted by Jake Biddix

i just realized that I put the strap screw on backwards, and of course I don't have enough thread left to install it the correct way...I'll have to adjust it this evening to get the strap screw on correctly. It kept on popping out the 1/4" jack, and I couldn't figure out why till I looked at one of my guitars!

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Yes I noticed that in your pic above. The strap button nut is on wrong, and there is not nearly enough of the switch jack showing. The threads of your nut shouldn't be showing at all - the threads of the output jack should be flush with the inner threads on the button nut. It looks like you need to loosen the inner nut that seats against the washers that seat against the tail block inside so more of the output jack threads will be visible on the outside of the instrument.

As far as "what to play on the OM" I say anything you can play on guitar. Besides Sierra Hull check out Sarah Jarosz, Cahalen Morrison and Eli West, Tim O'Brien, Darol Anger.....