Time for new tubes.. which ones?

So Sorry, they are 12AT7 the preamp manual says I can also use 12AX7 or 12AU7 as well. All I know is that the original tubes came from China. Thanks for any help.

What are the tubes, please?

My all time favorite 12AX7 tube is Telefunken smooth plate. For 6922, I have had good luck with Siemens. I think you need to try different brands in your own gear to decide what suits you the best. I would choose a good tube seller. I have had excellent results buying new and used tubes from Brent Jesse Recording. He is very helpful by telephone and has a very user friendly website.

Parrot,
The original stock tubes are supposedly a Chinese Mullard double mylar knockoff T7.

Koestner,
Look up the thread in the Archives-"Tube Rolling for TAD-150". Lots of suggestions there. I just found it recently myself and am looking for suggestions also-mine was the last post. I have a pair of Sylvania 5751s on the way to try. I have a pair of x7 RCA black plates in mine now and they are an improvement over stock. I am also going to order a new pair of Groove tube 12AX7Ms to try.

I own a TAD-150 and have tried various brands of NOS and used vintage 12AX7, 5751, 12AT7 and 12AU7s from the US & Europe. Right now I am using RCA blackplate 12AU7s. These tubes have excellent bass characteristics and do everything else very well. Another bonus is that the volume knob has much more play in it. 12 o'clock is now very loud insted of 9 o'clock. The 5751s would be my second choice. Good luck in your search.