Constant noisy tubes maybe go solid state?

@gochurchgo
 The tubes that I have been using are grey plate solid O getters!

I have that same preamp. I like vintage Ge 12ax7WA/6201 tubes. You should be able to get a matched pair from any reputable seller on ebay for less than 50 bucks!

The GE JG-12AT7WA vintage tube is a rugged, American-made workhorse produced for the U.S. military and used for computers and targeting equipment. This tube is usually very low in microphonics due to its rugged construction. The GE JG-12AT7WA had to work well under arduous conditions and was made with solid support rods and short, gray plates.

@aj523
Tube Depot is fine!
Google is your friend! Here ya go!

As tubes wear, some problems can come up. One of the most common symptoms is a ringing sound. This is usually due to the tube becoming microphonic. Like its name suggests, a microphonic tube is picking up sound and amplifying it.

Dual triode preamp tubes like the 12AX7 really have two separate tubes inside one glass envelope. When the plate current draw of each triode is the same (as evaluated by our VTV testers), we refer to that as having balanced triodes. These may or may not also have the same gain on each triode but are still considered balanced.

12AX7 tube is a high gain dual triode tube found in many tube amps. Because of the high gain, the 12AX7 tube is often used in the V1 position of guitar amps, which has a lot of effect on sonics. It is the tube that defines the sound of your amp in a big way.

@gochurchgo
Yes! The gain was too much with the cartridge that I use so I swapped to a lower gain tube in the phono preamp!

@gochuchgo
I have lowered the gain on my phono preamp swapping the 12AX7 with a 12AU7. You might see if you can do the same with the QS line stage!

12AX7 gain of 100
12AT7 gain of 60
12AY7 gain of 45
12AU7 gain of 19

@larry5729
Here ya go!
https://www.collectorsweekly.com/articles/could-an-old-school-tube-amp-make-the-music-you-love-sound...

@gochurchgo
" I think my system sounds better than it has any right to considering it’s all mid-fi stuff. "
 You should try the SYS in-between  the phono preamp and the preamp.
Why do you consider your gear Mid-Fi?

@gochurchgo
 Why did you get a 6201 tube if you need less gain than a 12at7? Just curious!

@ gochurchgo
I hate to burst your bubble but I think your spinnin’ your wheels. You said the problem was too much gain with the QS preamp. You are replacing the At7 with a 6201. Both of those tubes have the same gain. Good luck and all the best!