Are you referring to impedance coupling between stages? If so then there are 3 camps, as many SETs also use RC coupling.
Interstage transformer coupling is usually done to create circuit simplicity, but does so at the price of the effects of the interstage coupling transformer. This often results in a more lush sound, accompanied by a 'dynamic' quality. IMO the term 'dynamic' as I used in the last sentence is really more accuratly portrayed by the word 'distorted'. Not distorted in the sense of outright clipping, but adding unclipped distortion that ear reacts to as perceiving as loudness cues.
The effect is artificial, and once aware of it, I found it hard to listen to any but the very best SETs, none of which I found to have interstage transformers.
Interstage transformer coupling is usually done to create circuit simplicity, but does so at the price of the effects of the interstage coupling transformer. This often results in a more lush sound, accompanied by a 'dynamic' quality. IMO the term 'dynamic' as I used in the last sentence is really more accuratly portrayed by the word 'distorted'. Not distorted in the sense of outright clipping, but adding unclipped distortion that ear reacts to as perceiving as loudness cues.
The effect is artificial, and once aware of it, I found it hard to listen to any but the very best SETs, none of which I found to have interstage transformers.