Zotl for me is the elegant replacement. You can argue about the name and technology used (solid state devices plus transformers etc.) but once heard it is obvious an OTL by audio signature. It has all the holographics and air that we all love about the OTL. It is complex by nature so maybe not a diy’rs dream (more of a nightmare). But it is rewarding if you have a working prototype. Standard OTL look easy but are far from it especially when dealing with oscillations and high current loops etc.
Harvey Rosenburg came up with that acronym back about 1998. I pointed out that the Berning amp wasn't an OTL (although a brilliant design). He said he knew that and that the acronym had no meaning.
It referes to the fact that all transformers do have a hysteresis except his. Hence the name Zero Hysteresis Output Transformer Less, i agree the “less” is not a good choice as it is a double negative… on the Zero that is…
Because of Harvey i got interested in the Zotl in the first place. It took me many years to look at the schematic with different eyes as at first glance i also noticed the transformers and neglected it because of this. Much later i found that these transformers where just current sources for the audio part and not transformers in a normal sense (only for the rf part that is). Therefore the load is between the current sources and not a secondairy of any of these transformers.
Because of Harvey i got interested in the Zotl in the first place. It took me many years to look at the schematic with different eyes as at first glance i also noticed the transformers and neglected it because of this. Much later i found that these transformers where just current sources for the audio part and not transformers in a normal sense (only for the rf part that is). Therefore the load is between the current sources and not a secondairy of any of these transformers.
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'OTL' in the case of this thread refers to 'Output TransformerLess'. In the case of the ZOTL it does not, owing to the fact that an output transformer (air core) is employed. It was on this account that both David (the designer) and Harvey (the guy that created the acronym) told me the acronym had no meaning. Obviously many people have struggled to apply meaning where none existed originally.