The Leben D600 integrated amplifier comes with matched quad stock Sovtek 6L6WGC vacuum tubes. After break-in them for more than 100 hours, they don’t sound good in my system. They have the typical 6L6 sound. Strong bass and extended high with sibilance in my system. The midrange sounded recessed due to strong bass and high. I am using Harbeth M30.1 speakers. M30.1 is a neutral sounding speaker. It very transparent too. My Creek Destiny 2 (solid state) integrated amplifer sounded better than CS600 with Sovtek 6L6WGC. Destiny 2 has a very balance sound with just the right bass, mid and high. And no sibilance whatsoever. It is one of the best value for money integrate amplifier in the market. This means, I will be doing some tube rolling to find the most suitable tubes for my system. Below are the photos of those tubes taken in total darkness.
These photos are taken using Nikon D600 DSLR camera.