Installing a Martin 332 Thinline pickup on a Martin Backpacker

It's been a while since I've blogged anything useful. Actually, it's been a while since I blogged, so I might as well start by blogging something useful. For Christmas last year, I received a Martin Backpacker guitar (link to zZounds), which is a fun little travel guitar with a pre-puberty voice. Some people call it a mandolin, and some people call it a ukulele, but regardless of what it actually is, for me it's a travel guitar.

I had also been playing with an iRig with my full sized acoustic guitar. Combined with their Amplitube app for iPhone and a pair of headphones, I could turn my acoustic into an electric guitar and a set of effects pedals, which was good fun. Nonetheless, playing a full sized acoustic guitar at home has a benefit: You can play it nice and loud without any electronics, and it sounds great. The Backpacker, on the other hand, has nowhere near the volume nor the depth of a full-sized acoustic guitar, so the idea of amping it on the road with nothing more than a cable and an iPhone was very tempting.

Thanks to the Internet, I quickly learned a number of things:

• Martin used to make a Backpacker that came with a pickup! Apparently, it was an under-saddle "Thinline" pickup.
• A number of people had added pickups to their own Backpackers.
• From a number of discussion threads that I read, people couldn't figure out how to get their hands inside the Martin Backpacker to do all the necessary installation work for a pickup that would replace the guitar's end pin with a jack for the pickup.

Having thus done my detailed research, I stumbled upon a sale at Strings and Beyond (BTW - great store!) and promptly purchased the Martin Thinline 332 pickup. When it arrived, I carefully unpacked it, examined it, realized that I was in for more than I had bargained for, repacked it, and let it sit unused for four months. It sat unused until this weekend, when I finally decided that no seemingly impossible job was going to paralyze me with fear for significantly more than four months.

I'm going to make a long story short: Having read the instructions some 19 times, and having examined both the guitar and pickup in great detail over and over, I decided to follow the instructions carefully and thus, after five or so hours of work, I failed to get the deed done. I then used that failure as an excuse to buy more tools (since there are still a few that I don't own), thinking that I could somehow Rube Goldberg a complex collection of tools into reaching inside the body of the Backpacker and somehow doing what I was incapable of doing previously with my inadquate collection of twenty-odd thousand tools.

Fortunately, upon returning home with my latest tool acquisitions (which totally rock, I might add), I accidentally discovered the secret of how to install this thing! Realizing that there were at least three other people in the world who could benefit from this knowledge, I started taking pictures. And here's the "aha!" moment:

 

Yup, it's just that simple. The "outside" part of the jack unscrews from the jack. OK, you probably already knew that, but I didn't. It's nowhere in the instructions, which I had read at least 23 times by this point in the day. Previous to this, I had to figure out how to screw the rear retaining nut (shown on the jack above) and the wire shielding (not shown) onto the jack from behind -- while the jack was in its proper place in the guitar. Now, I could do just the opposite! I could put the washers and rear retaining nut on, screw on the shielding, and then just pop it out the jack hole and screw on the outside parts! (I could have saved so much time had I realized this up front!)

I'm not going to repeat what is in the tiny little instruction booklet; you can read that yourself some prime number of times. (The only thing you really need to know is that .094" is a 3/32" bit; that is important.) So, here's what I did:

1. Obviously, I started with the guitar strings out of the way, so I could get to the hole:

 

2. After I carefully (oops!) drilled out the hole, I used one of my shiny metal "hook" tools to measure the depth of the guitar wall to determine where the rear retaining nut would have to go. It turns out that you have to leave right around 20mm of thread exposed on the "rear" portion of the jack: 

Note that my jack didn't fit flush due to my poorly drilled hole. A couple of things to keep in mind (some of which I should have thought of myself):

• First, don't go straight to the 15/32" bit. Work your way up.
• Second, Google for some advice on drilling without messing up the wood; I'm supposed to know better myself, but I screwed this part up.
• Third, even if you do mess up the hole slightly, the end cap of the jack will hide a millimeter or two of mess.
• Lastly, if the jack doesn't fit flush, just get a round rasp and carefully widen the inside portion of the hole that is preventing the jack from sitting flush; only widen it enough to get the jack to sit flush!

3. Now, let's verify that the jack is ready to go! Use a long twist-tie (or string or wire) to keep this part simple:

Yes, that's a single twist tie that goes through the jack hole and out the sound hole. You're going to probably use this a few times! Let's see how the jack fits. First, we adjust the rear retaining nut to where we think it will be, and feed the jack through:

Notice that we can put that twist tie through the handy holes on the "outside portion" of the jack. I fed it through without the annoying washers and added a millimeter or so to account for that. If you do feed it through with the washers, save yourself some frustration and do so with the jack hole of the guitar pointed to the ceiling -- that way, as you feed it, the washers stay in the right place!

4. Once we've figured out where the nut will go, it's time to put this thing together! Time to get out the soldering iron. Tip #1: you can gently adjust the pieces of metal on the back of the jack to make room for your soldering work, which is especially handy if you're as out-of-practice as I am:

I stripped the wire by hand -- unfortunately, you don't need a fancy tool for this job:

 (Despite that, I bought a couple extra expensive wire strippers, just to soothe my grief.)

Twist the shield wire together, and keep it separate and out of the way. Bare just a few millimeters of the inner wire, again using your fingernails -- at the most!

OK, once this thing is soldered, we're not going to be able to put anything else onto the wire, so make sure you have the shield in place (i.e. the wire going through it!) before you solder:

 

(I know that's an obvious point, which is why after doing it wrong once, I didn't repeat that mistake all day!)

You can also trim the wire if you are so inclined. Here you can see that I stripped the wire before I trimmed it, affording me the chance to strip the wire for the third time:

Pre-tin the wire ends:

Solder them on:

 

(Notice the handy soldering clamp from Radio Shack .. these tools do eventually come in handy!)

Carefully straighten out the bent pieces of the back end of the jack, and then crimp the wire holding parts (so that the stress doesn't go onto the solder joints):

 

5. Let's assemble it! Screw on the shield, and double check the location of the rear retaining nut:

 

Remember to put the washers on in "front" of the retaining nut, and then attach the twist tie through the holes in the top of the jack:

Now, stand up the guitar so that the jack hole is pointed toward the ceiling, and pull the jack through!

 

(Here you can see the 2mm of collateral damage from my drilling escapades. Please ignore.)

And now for the easy part!

The only tricky part here is keeping the jack from falling back in while you do this, and keeping it from turning (which would eventually put a small amount of strain on the wire). I used my Long Pointy Tool (tm) to hold the jack in place while I tightened the front retaining nut:

 

And voila! The moment I was looking forward to:

In conclusion, this wasn't actually that hard of a project, but I did waste many hours trying to figure out how easy it actually was. I will say that the guitar appears to be made for this particular under-saddle pickup, which certainly helps. If anything, make the .094" (a.k.a. 3/32") hole in the saddle slot slightly large and more sloppy at the top of the hole so that the pickup has some slight additional room to vibrate; my first installation attempt didn't do this, and the pickup was unable to pick up the bottom E and A strings as a result. My liberal interpretation of the 5.9mm offset rule for the location of the wire hole also resulted in the high E string getting slightly less pick up than the adjacent B string. (Translation: In the instructions, "no less than 5.9mm" also happens to imply "no more than 6.0mm".)

When it was done and re-strung, I was quite pleased by the result, enjoying it with the iRig/Amplitube combo. Also, a slightly cheaper option than the iRig is the Woodees version. I prefer the ones that plug into the headphones plug of the iPhone, since that lets me concurrently plug a charger into the iPhone.

Hope it helps! Have fun!