Problem solved. Tonearm issue. Thanks, these responses directed me elsewhere.
I am happy that you sorted it out. As with other posters here I was skeptical about assuming it’s the SET amplifier at the heart of the issue. I use an 8 watt SET amplifier paired with 94 db (14 ohm) speakers. The sonic strengths of this are the purity, naturalness and ease. Yet at the same time very lively, engaging with good dynamic contrast.
Charles