Very pleased with results after installing Sparkos Labs SS3602 discrete Opamp in my Tube Dac, the Xiang Sheng Dac 01A. Its an older Dac but it soubds sublime and now even better. Immediately noticed difference, detail and Air increased as did the overall presentation of the music. Other Upgraded were a NOS GE Jan 5670 tube installed replacing stock Chinese 6N3. For Amp I was using my DIY TPA3255 class D and speakers were the NHT ST4.