[birdland]

Thank you for the quick responses. Let me clarify what I meant.

With respect to the KT120/KT150 tubes, they ring when you run your hand over them. My used REF 150 doesn't make a noise if I move it either. However, when I brought the amp to my tech who is authorized to repair Audio Research products, he told me how these tubes ring and showed me. He said imagine what a REF 750 sounds like when I run my hand over its KT120 tubes. He is not as enamored by the KT120/KT150 tubes as everyone seems to be. He doesn't like the fact that their innards seem to vibrate by design. He would rather have a 6550 tube if he had to have those types of tubes.

Keep in mind that he is more of a low power amp/high efficiency speaker kind of person so there may be some bias there as well. After all, who doesn't have their preferences in this hobby?

With respect to the REF 5SE and rattling/ringing, it is hard for me to describe the sound so rattling/ringing isn't exactly right. Also, I just tried to move the preamp on the Herbies Audio tenderfeet and it doesn't make noise either. I guess it has to be jarred harder than I thought or maybe the noise was easier to hear because I had the top cover off while I was working on it and moving it around quite a bit. It is probably not an issue.

Most likely, I'll bring REF 5SE to the tech I mentioned to have it checked out when I bring my LS25 over for a check up before I put it up for sale.