Zero Autoformers??? in Technical/Restorations Posted August 11, 2009 It converts speaker load impedence, for instance say you have a 4 ohm speaker, you put the Zero between your amp and speaker and this will let the amp see either an 8 or 16 ohm load. This is especially important with OTL amps because they work best with high imp. speakers. I've never used them but from what I've read there isn't any degradation in sound quality with them installed. Music Reference is now designing an OTL amp that will have Zero's built into the amp.