You guys must be talking about the newer vinyl pressings because the initial copy pressings on Atlantic Records were shite in '69. Praise the Lord and pass the ketchup when they released the 4cd re-mastered box-set in the 90's. There was a reason why they were re-mastered besides the obvious re-sales. Even as a young kid of 14 I can remember hearing the master tape hum in the background on top of the vinyl analog hum, which was constant throughout the whole album and
annoying as hell. 
I still have them & put them on when anybody gets starry eyed about the past & how good vinyl sounded compared to cd's. I put on the re-mastered cd tracks from the 1st album ...
the Led Zep II album was just as crappy... and they concede it was yeah, pretty bad.
One guy claimed it was my copies, so the next time I was over at his place I bought along the box-set and we did the comparison all over again with his albums, on his equipment. I continued taunting him until he cried uncle.
I can be such an a$$ at times.
But the dam band was so good they could of fed the sound thru a funnel and I would have bought it.
Remarkable and ground breaking; even if half the tunes were stolen whole cloth from Willie Dixon ...
Willie sued and won. Without those first 2 albums the whole Chicago/Mississippi Delta blues would have been a complete mystery to most of the white kids world-wide in the late 60's. The Stones were covering Chess/Dixon tunes in the early-mid 60's but none of those singles I believe ever cracked the Billboard top 10.
