First amp I ever owned was a 1505. Bullet proof. I have owned and still own many more (I think 4 more). I sold a 1504 recently, third owner, which was 20 years old and the DC offset on the binding posts was immeasurable and the bias was spot on. Morris Kessler has a philosophy of making things to last. I think ATI are some of the best SS amps out there despite the lack of audiophile jewelry and cache.