TUBES

Tube Depot, Viva Tubes, The Tube Store. Between these 3 providers, the tubes needed should be available. If it’s some odd tube, like ones yours truly recently needed, an order was placed to a man from the Ukraine on that auction site. 

Also, channels need to matched… so pairs, quads, need to be matched. There is a small charge to make sure the output is matched.

why buy new tubes? many, most last 10,000 hrs.

I just had my McIntosh mx110z tube tuner/preamp overhauled by Audio Classics. All 17 vintage tubes tested good, he left them all in.

You don’t know about the tubes that came in it right?

I advise tube users to buy a simple tube tester, which gives you knowledge, confidence, and, when trouble occurs, quickly find or rule out the tubes as the problems, as well as test what you buy, see how matched they are. My little tester always agrees with my big heavy one, I don’t bother with the big tester

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2505460.m570.l1313&_nkw=tube+tester&_...

You need to verify it has sockets for your tube types, and have the manual/chart/tube book to know the settings

https://www.ebay.com/itm/144072538321?hash=item218b6478d1:g:534AAOSwSYBgw6jt

like mine:

https://www.ebay.com/itm/224471092083?hash=item3443850b73:g:vPsAAOSw71Vgqada

don't let the rusty hinges scare you, they used poor quality metal to keep costs down.

Elliot is correct. These tubes are small, they last multiple thousands of hours. Particularly when you first get into tubes it is a little disconcerting. It is power amps that have shorter a tube life. But with modern equipment even these are getting longer. It is likely you will not face any tube problems soon. Personally, I would either not worry about it and just order a full complement if something fails or order a full complement and put in the closet. I have quite a pile of tubes I ordered just in case and traded the equipment before a tube went out.