The Alumitone pickup uses the aluminum metal frame of the pickup as the low resistance ¬“string loop¬” feeding two coils mounted under the frame that each have about 15000 turns of very fine wire. They are connected in parallel and are listed as having about 2500 ohms, meaning that each coil is about 5000 ohms. These pickups are designed to be used on high impedance guitar amps.
True low impedance pickups target the traditional low impedance microphone inputs listed as 150 ohms but can range from about 100 ohms to about 300 ohms. The typical microphone XLR input impedance is about 2400 ohms to act as a light load on low impedance inputs up to about 240 ohms, having an actual load 10 times higher than the actual output impedance.
Low impedance pickups using a transformer are using a current based concept rather than a voltage based concept. For the current based approach to work, you need a string loop with very low resistance to develop more current in the primary transformer string loop with the magnet in the center. This means using very heavy copper wire with a very very, very low resistance joint to maintain a high current in the string loop.
AWG 8 wire has 52 micro ohms per inch resistance. A typical. String loop, including the part that goes through the transformer is about 8 inches long. 52 micro ohms is .000052 times 8 or 416 micro ohms. If you use a 500 turn current transformer with one turn on the transformer primary, you must square the turns ratio to calculate the approximate output impedance. 416 micro ohms times 250,000 is 104 ohms which targets a microphone input very well. This assumes that the AWG 8 wire string loop has a very, very, very low resistance joint forming the string loop.
Most of the YouTube videos do not mention these details. See my thread ¬“Low impedance pickup research¬” for more details.
Use a Triad CSE-186L current transformer but remove the primary windings of three turns of AWG 16 wire to reveal an opening that will allow the AWG 8 wire to be bent into a hairpin loop to extend under the guitar strings with a magnet in the center. The challenge is to make a good low resistance joint to complete the string loop using a copper crimp sleeves with silver solder. Use two conductor shielded microphone cable with the two transformer outputs going to the inner conductors and the shield going to the string loop. On the XLR side make pin 1 the shield connection, pins 2 and 3 the transformer connections. This design allows you to slip the pickup under the strings to try it out with any changes to your guitar. Just feed it to an XLR microphone input or an XLR Shure A95U series mic matching transformer.
This should get you going in the right direction.
Joseph J. Rogowski