Designing an Electric Hammered Dulcimer
A long time customer who plays one of Linear Chromatic Hammered Dulcimers in his band The Botanist requested I make him an electric hammered dulcimer. His instrument was currently amplified using one of my internal film piezo pickups
connected to an internal preamp and internal 1/4″ jack. The set up worked OK but not as well as he’d like when playing in a very loud environment where there was a complete drum set and the necessity of high volume. He really needed pickups which did not rely on either the vibrations of the air (mic) or the instrument members (piezo). The exploration began. I thought we might have to move away from using an acoustic instrument as a base and instead take cues from the electric guitar eliminating or at least minimizing the acoustic capabilities of the dulcimer. Most electric guitars except the acoustic /electric use solid wood bodies. Doing some quick calculations, I determined that an instrument the size of the LC Linear Chromatic) even using a light wood like basswood, would weigh 55 lbs. Given the amount of strings and tension generated by a 7/19/18/9 LC, I was even uncertain that the construction using solid wood was up to that amount of tension without warping and the resultant tuning problems. I decided to instead explore using a torsion box style of construction utilizing a back and sound board of ply with the interior space being occupied with polystyrene foam cut to fit. I proceeded to create prototype 15/14 utilizing that method of construction. For pickups, I began exploring the possibility of using piezo cable which relies on compression to generate an electric signal. This material is available from a number of sources. Probably the easiest would be Windworld. Cable piezo is the same material that is often used in under the saddle transducers in guitars. I did some experiments to determine the viability of this pickup. I decided to create a slightly deeper saddle on my main bridges where the cable piezo would reside underneath a conventional 1/8″ acetal saddle. The string bares down on the acetal which in turn compresses the piezo cable.The cable runs the length of each bridge and is wired together in series to an internal preamp and then out through a internal 1/4″ phone jack.The internal preamp needed to be one which could handle the four separate piezo cables (one for each of the four bridges on the dulcimer. I did a lot of searches and came up with a very compact unit that could accomodate as many pickups as I needed (and more) each with individual volume control made by a German firm. Of course in my excitement in finding all this initial functionality I didn’t think about the ramifications of lowering the holes in the bridges by 1/8″. The holes in the bridges obviously allow passage of the strings when there are two or more bridges and there must be enough clearance so the strings don’t make contact with the bridges.
Unfortunately with the way I construct my bridges, I needed that 1/8″. There was no way I was going to get enough clearance. I had to scrap the idea of using the cable piezo’s embedded in a slot in the bridges. Another possibility which I did not explore very far was embedding the piezo cable in the low side bridges. This would allow the same bridge configuration that I normally use.
A change in direction
About this time I got a lead from a friend Bob Wey about a guy Charles Hepinstill who makes humbucking magnetic pickups used for amplifying acoustic pianos. Bob thought that this might be an avenue to explore. Apparently hammered dulcimer player Malcolm Daglish had explored this type of pickup on his instrument back some time ago. Malcom decided that even though the pickups worked, they did not give the quality
of sound he was looking for. The needs of my customer were quite different then Malcolm’s. I contacted Charles and decided to explore how we might install this type of pickup on a Linear Chromatic. Magnetic pickups of course isolate the source of vibrational energy to the vibrating steel string which effects the magnetic field created each pickup. They do not rely on the vibration of the air or elements of the instrument such as soundboard and bridges. As result they demonstrated the potential of not being influence by any external vibrations with no feedback, making it ideal for the customer’s needs. I sent a protoype acoustic model to Charles so assess where we might place the pickups given the configuration of the LC. Here is what we came up with. All the pickups where custom sized and located under the strings.
The two left and right long pickups handled most of the work with the center pickup taking care of the the 7 treble courses of the bridge T2. Once the location and appropriate lengths had been determined, the only variable left was the the height or distance from the strings. The pickup surface had to be at maximum 3/16″ from the string. The closer you get to the strings, the more response you get. I created shaped wooden shims that I dimensioned to create the clearance desired. I had to play with the relative heights particularly of the center pickup as this was the only way to get a balanced sound (volume). Once the heights were OK, I attached the wooden shims to the pickups with double stick tape, sprayed the pickups black since their natural color is bright yellow. I then drilled holes through the pickups, so I could mechanically attach each of the pickups to the instruments soundboard with brass screws. This must be done carefully as you can only drill through the magnet not the wind. A break or short in the wind destroys the pickup. I know. I did it on one of the pickups and had to get a replacement. Once the pickups are mounted, I drilled holes for snaking the wires inside the instrument connecting
them in series to a small transformer and a 1/4″ phone jack all located inside the instrument. One last change had to be made to my Linear Chromatic before all this would work. Magnetic pickups only respond the movement of steel. As a result I had to replace all the Phosphor-Bronze strings with steel and all my Bronze wound strings with Stainless steel wound strings. After doing all that we had a pickup system that did the job.I have more information including a video and sound samples available on my website. If you have any
comments, send me an email.