Very Simple Musical Interrupter for driving dual Tesla Coils in stereo from Direct Audio. This is a custom variation of the original Dual VSMI 2.0 by Grégory Gusberti and Fabrício Franzoli as found on Alex Yuan’s website: http://www.personal.psu.edu/ahy5028/coiling/Schematics/Dual_VSMI.jpg. I built it to see how it compares with my other attempts at making a decent direct audio interrupter for Tesla Coils.
All ICs are TSSOP packages. All resistors and capacitors are 0805 footprint, with the exception of C6, C12, C13, C15, and C17, which are 1206. The LEDs are 1206 package. All thru-hole components (i.e. the connectors and potentiometers), plus the two LEDs, mount on the bottom side, which is designed to be the “top” in the final assembly.
To the original design, this version adds a headphone/speaker monitor output and fiber optic transmitters for driving a Tesla Coil control board. Reference designators have been kept in sync with the original schematic referenced above.
Errata: The 10K “Sensitivity” potentiometers, RV1 and RV3, operate backwards – turning them CCW increases sensitivity and turning them CW decreases sensitivity. Additionally, the Sensitivity potentiometers really do little to nothing at all, as the only time it will detect the incoming signal is if you crank the volume on your device to max and turn this circuit to maximum sensitivity. This seems to be a design flaw in the original circuit. So you might as well skip the Sensitivity controls and tie them directly to ground or do a fixed-resistor divider network like their other circuit variation at http://www.personal.psu.edu/ahy5028/coiling/Schematics/VSMI_REVB.jpg.
Also, the high-impedance DC-coupled pull-up on the inputs causes some phone/player type devices that use the bias/loading on their headphone jacks to detect connection/disconnection, to incorrectly think you have unplugged the cable from the jack. In other words, it can’t detect that this device is plugged in. My Android Samsung player device behaved that way.
Otherwise, it does function. The quality of the chopped audio, though, isn’t nearly as good as I had hoped. It’s comparable to several other attempts at a direct audio interrupter.