A very boring yet crucial part of any setup. A buffered multi always comes in handy and it’s pretty easy to build as well. Since I was building one myself I added a few leds to indicate signal and it’s polarity, that way I got some indication what’s going on. I used 2 separate leds since I didn’t have any dual coloured leds lying around. It would look a bit fancier with a dual led, maybe I should order a few, just in case I build a few more of these.
A single quad opamp configured as voltage followers handles all the buffering, the fourth one drives the leds and is configured as a comparator. I used a TL074 since I have tons of them lying around, but most quad pampas should work just fine.
*usual disclaimer applies. So I’m not responsible if you accidentally break the time-space continuum.
update 30-10-18: A facebook user pointed out a serious error in the schematic, it’s fixed now.