What do we think of Shuguang tubes? I decided to find out for myself and ordered a set of metal base 6SN7s and a pair of 6AS7Gs - $20 shipped for each pair. On first listen, the 6SN7s sounded lean and mean. Talk about sibilance! OMG. One could slice bread with the sound. ~100 hours of burn in, and the highs mellowed considerably, the mids became sweeter and slightly more transparent, and the bass stayed just as lean. I'm going to give them another 100 hours in hopes of the tubes becoming more transparent and the bass being more fleshed out. There's definitely some promise here. On first listen, the 6AS7Gs sounded just like the driver tubes - lean and mean. 50 hours of burnin did nothing. Gave them another 24 hours; nothing changed. These tubes sound like crap. I guess I'll keep them for a spare pair. Not even worth the $20, as for the same money one can have a decent pair of 6080s.