I changed out the Tung-Sol stock tubes with Tung-Sol 12AX7a/12AX7 NOS Tubes and wow what a difference. I have Triangle Titans, Audio Quest Bedrock Bi-wire speaker cables and a Martin Logan 400 sub. Before the system was bright with excessive high end and ok bass. After I changed the tubes and the power cable, I could not believe the difference. The highs were still great but much smoother. The bass really kicked in. This is a second system that now comes close to my expensive main system with VR4jrs.