Direct Coupling will add tremendous sustain to your guitar, It will also give you up to 25% more audible overtones.  You can really hear the difference!

I have done at least 20 Blindfold tests and even non guitarists can hear the difference.

Direct Coupling defined would be the process by which direct contact is made between all the parts on a guitar that could either add or subtract from the tonality and/or sustain.

It has been said, that if a guitar is directly coupled, it will most likely be neck through body construction, a solid mounted Tone/Pros Bridge & solid mounted pickups.

I will state for the record. You can also achieve direct coupling with a bolt in style neck like a PRS or Quicksilver. To do so you must adhere to several strict rules.

1, No paint, finish lacquer or glue can be present anywhere in the neck-pocket.

2, The neck pocket has to be extremely tight and 100% stable.         

Another way to achieve Direct Coupling would be to use a deep set mortise & tenon like a Gledura or a Jaros. The rules to apply here are as follows;

1, The pickups need to be hard mounted to the actual neck wood.

2, There must be no glue on the top of the deep set neck, and it must be a tight fit, there has to be a way for the bottom of the top plate to come into direct contact with the deep set neck.

3, The tenon must extend at least to where the bridge is located. There must be direct contact with the studs in the bridge through the top and into the deep set neck itself.