JJB Prestige 220 Mandolin Transducer Installation

JJB Electronics

An "F" style mandolin is used for this JJB Prestige 220 installation, but most any "F", or "A", or hybrid style mandolin will work with the following installation procedure.

Internal mandolin sound board (top) bracing can differ in design and construction. This "F" style mandolin's top is cross braced, which allows lots of room on either side of the centers of the "F" holes to place the transducers. Other "F" mandolins will employ other top brace designs that will only allow the transducers to be installed slightly above the "F" hole centers - this will not be an issue with the JJB Prestige 220 mandolin transducers as long as they are placed at the same "F" hole top locations.

There are at least two methods for installing the transducer strap jack. This installation mounts the transducer directly on the tail piece by enlarging its hole. Another method would require recessing the strap jack's mounting nut into the body tail block, and then mounting the strap jack's cup to the tail piece.

Remove the tail piece and strap button.


Drill out the strap button hole with a 1/4" drill bit.


Ream out the strap button hole with a 1/2" end pin drill or 1/2" drill bit.


Mount the tail piece on scrap wood, using the tail piece screws.


Use a 1/2" bit in a drill press or electric hand drill to enlarge the tail piece strap button hole.


Smooth out the tail piece hole with a hand reamer and/or file. Make sure the strap jack easily fits into the tail piece hole.


Mount the tail piece back onto the mandolin body.


Remove the strap cup and cup washer off the strap jack. Leave the strap jack's nut, flat washer, and star washer on the strap jack body. To keep them from sliding off the strap jack, you can keep them retained with a bit of candle wax or small piece of tape.


Using a long and thin BBQ skewer (or thin dowel with a point, or length of coat hanger wire, etc), push the skewer into the jack hole, put the strap jack through a "F" hole and into the mandolin's body, and looking through the "F" hole, put the point of the skewer into the strap jack's opening. Use the skewer to guide the strap jack into the tail piece hole. This sounds a lot harder than it actually is. TIP: with the mandolin lying flat on a table, once the skewer is pushed into the strap jack's body, tilt the mandolin's fingerboard vertical (upright) to allow both the strap jack and skewer to be directed through and out the tail piece hole.


STOP! If the body of the strap jack extends beyond the tail piece, it's too long. If the threaded cup part of the jack is barely showing, it's too short. We want the "step down" transition area of the large diameter threaded strap jack to the small diameter strap jack mounting thread ...
... to be slightly recessed before the tail piece (inside the body, just behind the tail piece. Measure how much this "transition" threaded area is either outside or inside the of the tail piece, remove the entire strap jack, reset the nut and washers on the large threaded body of the strap jack either shorter or longer, re-thread the strap jack back into the body and out the tail piece hole, using the skewer.

Thread the washer over the small diameter threads of the strap jack, screw on the nut, put a thin nail or allen key into the small side hole near the end of the strap jack to keep the strap jack from rotating as you wrench down the strap jack mounting nut.


Strap jack installed, let's move on to the transducer installation!


Tape down one of the transducers to one side of the mandolin top. Use a thin wire or mandolin (or guitar) string that's been threaded through the opposite side "F" hole into the body and out the other "F", grabbing onto the free transducer.


Pull the wire and transducer out the opposite side "F" hole and tape it to the mandolin top.


Strung up, tuned, intonated - this will make sure that the transducers reside under the top wood and close to if not under the bridge's feet.


The back of each transducer needs a tape or putty of medium strength applied. In this instance, a small square of 3M Concrete and Patio tape is used on the back of each transducer.


After the backing on the tape is pulled off, the short end of a hex Allen key is placed on the exposed tape and squeezed to make sure the bond is at least enough so that the transducer can be moved about without falling off the key.

For protection from the glue, painter's tape is applied around the top area where the transducer will slip into the "F" hole. The gold face of the transducer is cleaned with a piece of paper towel and a bit of alchohol or lighter fluid. A thick viscosity super glue, in this case 3m Scotch Gel, is liberally spread on the transducer face. This will insure that any minor curvature of the top wood will be gap filled by the glue.

The transducer is slipped into the "F" hole ...

... and lifted up to contact the top. Hold for at least a minute - or two ...

... or, if the "F" hole opening will allow, use a nifty swivel pad spring clamp and let it do the pressing work!

All done ...

Tutorial prepared by Rob DiStefano