[8-6-71 for me]

Has anyone swapped out the tubes, and if so did it make a discernible difference?

[Jon S.]

I never especially liked how the stock V1 tube sounded. Don't get me wrong, it was OK, but I'm shooting for blows me away. I keep a small stash of replacement preamp tubes on hand, both NOS and new build. After much experimenting, I went with an NOS Raytheon 5751 and upped the gain control correspondingly from 5 to 6. As always, of course, it's a personal decision and YMMV.

[wpmartin1979]

Has anyone swapped out the tubes, and if so did it make a discernible difference?

Swapping with a NOS RCA, Raytheon or Tung Sol USA will always make a huge difference. I have been liking the long plates lately, but like Jon says, it’s just a matter of taste. You will hear a big difference though IMHO.
I don’t have an SMS JG but I swapped out the tubes in my other preamps (Shiftline, blackbird, blue tube) and made a huge difference.

[wpmartin1979]

[8-6-71 for me]

The RCA tubes blew me away. Now it sounds and feels like a Twin pre.

From brittle to brilliant. Thanks for the advice, guys.

[NSP]

The RCA tubes blew me away. Now it sounds and feels like a Twin pre.

From brittle to brilliant. Thanks for the advice, guys.

Where did you source them?

[8-6-71 for me]

The RCA tubes blew me away. Now it sounds and feels like a Twin pre.

From brittle to brilliant. Thanks for the advice, guys.

Where did you source them?

https://www.ebay.com/itm/NOS-RCA-12AX7A ... 2749.l2649

[Smolder]

Comparisons are hard for me. For an important fender (ish) amp, I just automatically dig through the pile and find the best RCA or GE preamp tubes and go.