I’ve been rebuilding one of my 6550 amps and here is an interesting info on matching power tubes.

First image shows slightly unmatched tubes (prefect match in IP, but 10% mismatched GM). Notice that the amp reached 1% 2nd distortion at 44 watts.

If you have tubes that have a fragile silkscreen (practically all old stock tubes) and you put them in boxes, the silkscreen will be rubbed off every time you take the tube out of the box to use it or just to look at it :). To save the beautiful silkscreen from wearing off, just use a small plastic bag. I use 2×3 inch bags I get from Amazon. Put the tube inside the back and then insert the tube back into a box. It fits even very tight fitting boxes. Now you can take out the tube without being afraid that it will be damaged.

Another post in a series of legendary tube brands. This time I will go into details of General Electric (GE) Five-Star Brand.

Practically all tubes in the Gold Brand series have earned legendary status among audiophiles. In this article, I will go into details of the brand and what makes it so special.

There are so many great tubes with what’s called Foil Getter. But what is it? How does it look?