It's interesting that some amps seem to cause problems more than others. Is this a case of solid state vs tube? If that were the case it would be even more interesting and even potentially worthy of its own thread.
I am a guitar player and know that many people find tube guitar amps more sonically pleasing. The idea that tube amps may be less irritating (from a medical perspective) is intriguing.
I think it can possible be a tube vs solid state thing because I haven't experienced anything to tell me otherwise so far and I've been told similar things by other people. It's something that needs be looked into more in-depth. Some tubes amps I heard were much harsher than the ss amp but the tube amp still fatigued me less. Harshness on tubes just comes off as an unpleasant sound to me. On SS amps it's like my ears build up a defense(clogging and ear wax) to their sound no matter how smooth and warm it is. I have been told that tubes are easier on the ears. Maybe it has to do with how the amps handle distortion and clipping differently. So for people with especially sensitive ears, it may be something to look into. Listening to a tube amp after dealing with clogging from listening to a solid state device my ears slowly pop and the clogging eases up with each pop my hearing slowly goes back to normal.