It always seems wrong to cut a big hole in the side of an old acoustic ................
I actually usually try and talk people out of it when they want an on board preamp and EQ in an old acoustic guitar. I usually recommend putting in a piezo pick up under the saddle and a combined output jack/strap button as these are two small holes in less intrusive parts of the body and can be reversed fairly easily, well,much easier than a big square hole in the side. With this set up you can run an off board pre/EQ/DI and do the same thing without the "damage" to the guitar.
The other issue with the big hole is it can sometimes effect the tone of the guitar. Not a lot and sometimes nothing you can notice, but I've had customers who have owned acoustics for 40 years who say the tone changed slightly after the job was done.
Anyway, this was an older Maton acoustic and not particularly collectible or expensive, although I must say here that I personally think these eighties and early nineties Maton EM's are still some of the best acoustics I've played. They always sound great and you can get the action very low on them without buzzing or loss of volume.
So, first thing to do was "cut a big hole" in the side. I ordered a new Maton AP4 from Maton and after a bit of messing around it was ready to fit. I don't cut ANYTHING on a guitar any more until ALL the parts being fitted have arrived so once it was all here it's a fairly simple job to cut a nice square.
This guitar also had a neck joint issue probably from leaving it in a hot place.I see this every summer in Brisbane where acoustic bridges have let go and/or the neck joint has moved like this.
The bridge was still fine but this gap was evident even without string tension which indicates that the joint had let go and then "reset" itself in this position when it cooled down.
It's a fairly simple repair that involves cleaning out the gap carefully and re-gluing it back in the right spot. Sometimes you need to re heat the joint to actually move it back into position.
Once the neck is set and clamped it's left to dry and I move onto other work. It'll be in the clamps for a couple of days and then after a small clean up will be ready to string back up.
If you get this wrong or don't get the neck back to it's original position (assuming it was done right at the factory) you won't be able to set the guitar up and you will need to re-set this joint again in the right position so a little care now goes along way.
With string tension back on the joint was great so it's a simple set up and test the new pre/EQ and we're right to go.
Like I said,these are generally great acoustics to work on and set up and this one was no exception. It plays GREAT.