[roguegeek]

First, if I've posted this in the wrong spot, I apologize. It is a question about amplification, but maybe there's a more specific place to post?

I recently purchased a Schiit Lyr and one of the things I will be wanting to do is some simple tube rolling to get that experience under my belt. Well, I know very little about tubes and the guides I have read so far have done little to answer what I think should be basic questions. Maybe you guys can point me in the right direction.

• When purchasing tubes from sites such as ebay, the sellers usually post ratings on how they've tested. Examples are things like 80/90, 70/60, and 90/75. What do these numbers mean and what is considered good, bad, and average?
• Is it generally safe to buy new old stock and used tubes from ebay? Are there reputable dealers everyone here buys from that I just don't know?

Thanks for any help you all can offer.