Right now it is Rafael Kubelik, Berlin Philharmonic - Wagner - Siegfried Idyll, Die Meisterzinger von Nurnberg, Tristan und Isolde, Prelude and Liebestod.
My Teac X-1000R has no problems with treble
Turn the box over and read the large print and see the Prelude to Act 1 of Lohengrin followed the siegfried Idyll