But at low gain, the breakup just doesn't sound nice to me

I was pleasantly suprised at the warm, soft breakup, inflection and response when backing off of the volume and tone on the guitar.

After putting in the new Tung Sol in the preamp, its like the amp came back to life, sustain is richer and breakup is both "lively" and smoother

The clean channel doesn't break up as early as with the stock tubes (which is what the lead channel is for anyway)

used in an ART Tube MP Preamp, works and sounds really nice, as good as or better than the JJ it replaced