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What is the make and model of your amp so we can Google it.

Mullard CV4003 from Upscale Audio. My favorite 12AU7 and variant...

https://www.upscaleaudio.com/products/mullard-cv4003-12au7-vintage-new-old-stock?variant=22618913669

I have several amps that take 12AU7s my list is as follows
1: Amperex Bugle Boy ( super detailed)
2: Amperex (Long Plate Large D Getter)
3: Mullards (blackburn factory)
4: NOS Vintage RCA Clear top

What is your budget?

The Amperex 7316 is my personal favorite, but pricey.

I also like the RFT 12AU7.

On the domestic side the black-plate 5814s are an excellent value.

I tried the Mullard 4003 tubes years ago sourced from Kevin Deal.  They sounded fine (a bit rich) but became noisy faster than expected from experience with other tube brands.

I have been using Ron Sheldon's Cryoset Gold Lion 12AU7's but  since Ron's unfortunate illness caused him to shut down his business, I just purchased a matched pair of new production Tung-Sols from Tube Depot.  When the time comes we'll see how they sound.

I may be a bit fortunate in that my tube gear doesn't seem that sensitive to the tubes used.  More a question of longevity rather than tonality.  I suspect from the experiences of others, that Power Tubes have a greater impact on tonality and dynamics.