Time for new tubes.. which ones?

If you tell us what tube types they are (not brands, but tube #s, i.e., 12AT7, 6922, etc) and what brand is in there now, we can probably help. Otherwise, no chance.

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.