voltage = 11.24 - (0.182 * setting)fits the behavior almost exactly. The problem with this signal is that the neons have to be on when the voltage is less than some amount and off when they are greater than some amount. Passive SSRs only switch on when a voltage exceeds their threshold, so wiring directly to an SSR will get you neons which are inverted.I tried inverting the output signal from the SSR using a mechanical AC relay using the normally closed connections. This worked, but there was a loud click from the relay whenever the neon was switched on or off, and there was a small delay (on the order of 10s of milliseconds) between the game wanting to switch the neons and the neons actually switching. For a rhythm game where the neons flash to the beat, this wasn't acceptable. In order to do the logic conversion on the signal line, there needs to be DC power (12V or 5V doesn't matter since you can use a simple voltage divider to convert the signal from the game to whatever range you want). I didn't want to run a line from the power supply in the game up to the speakers because it would add additional non-standard connectors to the speaker connections and make it harder to disassemble or move the game. So I decided on purchasing small 5V switching regulated power supplies and connecting them to the AC line used to power the neons. Then, I divided the game voltage from 12V to 5V using a resistors and fed that to a comparator circuit as included above. Using the 5V from the power supply to power the circuit as well as provide the reference voltage to compare allowed me to use the trim pot on the power supply to adjust the circuit to turn on at exactly 32 and off at exactly 31 in the service menu. A block diagram of this setup is included above.Note that with this approach, you want to tune both sides so that when 32 is selected in the game the indicator light on the SSR is fully lit, and when 31 is selected the indicator is fully extinguished. If it is partially lit, you might get flickering at that value. Also, since the game attempts to use the dimming feature, if you have the thresholds set differently, the neons will come on and turn off at slightly different times which doesn't look as good. Also note that it is recommended to use the same neon transformer on both sides or the electrical characteristics of different neon transformers could also cause the neons to flash slightly out of sync from each other. For my conversion, I used two CoolNeon NG.A206GL 6kV 30mA neon transformers. The final result can be seen above. I used the original connectors from broken original transformers to avoid chopping up the wiring inside the speakers.