I know, I know, one more post about Hiss. I have an all original blue sparkle ser # 21338 with original cable, foot switch and manual with vinyl near mint except one very small, you guessed it, cig burn on top. I replaced power cord to 3 prong, kept the original for some fool who might want to put it back. All other components are the original. So I want to know what is acceptable hiss. I have heard that these amps had some hiss when new? I am looking for a baseline decibel reading for hiss that most would assume to be acceptable. Example, place iphone with decibel app mid speaker height, 2 feet in front, volume knob 1/2 way up with bass, treble centered and reverb off. Seems like this would be good information to use to determine where your amp is in terms of acceptable hiss. If you should not have any then I guess this is a mute (ho hiss) point. Looking forward to thoughts. Hugh Gibson, Vermont.