OTL's are usually more expensive, have many tubes - expensive tubes (high current triodes), consume a lot of power, may not perform the same with different speakers, and may not even work with some speakers. Those are, in very general terms without a specific make, the downsides (inconveniences, IMO). The huge advantage is the absence of the output tranformer which means the total harmonic distortion is almost non-existent. That's what gives 'em that incredible sound.
I disagree with tubegroover about a disadvantage being that they run hot. That' a characteristic of Class A operation, not the OTL topology.
I disagree with tubegroover about a disadvantage being that they run hot. That' a characteristic of Class A operation, not the OTL topology.