Went to buy Vandersteen 2C speakers and came home with a conrad-johnson Premier 11A.

Using a Variac is a great idea. Might also be a good idea to have the tubes tested before cranking up the Variac.You'll find out if there are tubes that need replacement and also how long it will be before the good measuring tubes go bad. It is a bit difficult to find a tube tester. A local electronics repair shop may have one.

Replacing the tubes will give you a fresh start.

I'm not sure if there are any electrolytic capacitors in the circuit. Since this amp is about 30 years old, those caps could be aged out. The non-electrolytics are probably OK.

It's also good to do a visual inspection inside especially the tubes. Do any have a grey coating? Or a crack in the glass bottle. Or not fully engaged into the socket.

@knotscott @kevemaher thank you for replies. 

I’m in KC. 

The tubes look excellent.  I was told that the amp was retubed and the owner only put maybe 40 hours on them. None of them have a gray coating. 

I’m OK with buying a variac, but I’m not sure what to get. Below is a link to one that puts out higher amperage than the $60 model that I mentioned.  Would this work? 

https://www.amazon.com/gp/aw/d/B07JV8ZCG8/ref=ox_sc_act_title_1?smid=A3GRIWLFOYL9K2&psc=1

If Google is correct, the amp has premium polypropylene capacitors. 

Not sure if this will work, but below is a link to photos. 

https://photobucket.com/share/a82604ef-7eb0-4b7a-bfd5-73b401495ae6

@sls883 Either of those variacs should be fine.  

The amp and the tubes look really good in the pic. 

@knotscott cool.  I ordered the better model of variac.  I figure it might have more uses should I ever need it for something else.

At what voltage should I start?  How slowly do I increase voltage?