I am considering adding a tube buffer to my system. I would place it between my 990 and my 7500. However I was wondering would just adding it to the main speakers be sufficient or should I look to add one to all channels? Obviously if my only concern was 2-channel listening I would just add it to the mains, but I do listen to a lot of multi-channel SACDs. I was wondering if just using a tube buffer on the mains in this mode would cause some disparity when listening to multi-channel. Also, if you do add it to all channels does that include the sub as well?

Another question is in regard to tubes (I have never been a tube owner), I understand they take sometime to warm up before the function properly. Therefore, do you just leave them powered on at all times or do they warm up relatively fast? Which is better for longevity, powered on or power cycling them?

I am planning on going with the Yaqin as it seems to have good reviews and a reasonable price for an experiment.

Any feedback on this subject would be appreciated.