Yaqin Tube Buffer

I still think the primary purpose of a tube buffer is impedance matching ala autoforming, to use between the source and amp. I would ask Pacific Valve who I believe Advertizes here. I agree though with Elizabeth the the two tube 6SN7 model is prolly the best if it does infact introduce a tube sound. Tube sound however is frequently squashed by the SS amplifier if that is what is downstream.

Again, it will come down to which component pair will benefit most from the buffer's ability to allow the recipient component to "see" a very low impedance. I think that usually means the buffer between the CD player and preamp is best. Hey, it can't hurt to try both and hear for yourself which of the options sounds best. As for your number 2 concern I think it irrelevant if your Dac is none oversampling with regard to a buffer. I just can't see why it should matter.