What is tube rolling?

Theo basically has it right.

It is basically just substituting different tubes from the stock tubes that came with the unit. Typically this yields different sonic results depending on the tubes. Usually better results, but sometimes worse. (Typically, but not always, NOS (New Old Stock) tubes will yield better results than current production tubes, since they were manufactured during the peak days of tube use (i.e. in the '50s and '60s). And, as you can imagine, NOS tubes tend to be much more expensive than stock tubes, (and get only more expensive with time, since they are slowly but surely getting more rare, as the supply is used up).

To get an idea of the sonic differences between tubes, check out Joe's Tube Lore @ Audio Asylum, (to which I have provided a link below).

Joe's Tube Lore @ Audio Asylum

I hope that helps!

I agree.I've never heard the term used for anything different
in audio.

I also agree that you should read, (and reread) Joe's Tube Lore at the link provided. It's pretty much the bible for the different ways tubes sound.

Just remember that the actual component that each tube is used in, makes a BIG difference. I have never found the same tube(s) sound the same in different gear.

I really like the Amperex USN-CEP 6922 tubes in my DAC, but they suck in my phono preamp. Each circuit and the way it "uses" each tube is completely different.

check out sonicfrontiers.com Go to the anthem side of the site and search for "A Taste of Tubes". It will teach you a lot of basics.

One of the oldest of audio addictions in the quest for perfect sound. the addiction is gradual and eventually leads to bankruptcy, but at a much slower pace than power cables, interconnects, and speaker cables!