Thanks to Charlie King for the modification. The RS1500 now uses Pro Nortronics narrow gap playback head direct wired out (bypassing the 2/4 track switch) to the tape preamplifier. The new Nojima sounds awesome and really put the stock head to shame :( Bass never knew had. Much better resolution. Far better extension at both extremes. Great dynamics and transparency instead of the sort of murky, forgiving, slight veiled sound of the stock heads.