Just putting this out there as an FYI. One can put a quad of Tung Sol KT-150s in the Jolida 502 series amp or integrated without it blowing up. Be sure to lower the bias before putting in these tubes. Also if you have the tube cage it won't fit over the amp because of the height of the KT-150s. That may be a good thing due to the amount of heat your Jolida will put out with the KT-150s in place. As for SQ I like the 502P even more with the KT-150s in place. They replaced a set of Blue Glass JJ KT88s which had a little bit of a boomy bass in my system. With the KT-150s in place the bass was tighter and the highs were more open to me in my system.