Magnetic Sensor Systems (solenoidcity.com)
E-66-75 Tubular Electromagnet
AWG 30 (8.4 ohms), infinite duty cycle
The Magnet Source
Ceramic Magnet Blocks
Rack and suspension system:
Assembled entirely from equipment purchased at the hardware store.
Wood bar: a 2×4, 48 inches long
Track: a bi-fold door track with sliders. The sliders, to which a door would normally be attached, worked nicely to allow the electromagnets to be positioned at any point over the width of the piano.
Metal brackets: about 4 inches long.
The bolt is held in place on the bracket by two opposing wingnuts, one on top of bracket, the other the bottom. The height of the electromagnet is adjusted with these wingnuts.
12 Vellman, Inc. 7W mono audio amplifiers (Mfg# K4001)