LDR Active Preamp - does it exist?

Your best bet is to deal with your gain issue at the amp. Choose one with higher input sensitivity and a passive line stage will match just fine, no extra gain needed.

Shakey

I already owned the amp which input sensitivity at 4V. These amps practically eliminate the use of passive pre, even using Tekton Lore speaker rated at 98 dB, still does not provide enough loudness and dynamic. It would be a surprise to me that no other commercially available active preamp (tube preferred) that utilized LDR volume control.

Pretty much any balanced or single-ended tube preamp with a volume control of up to 100K impedance can be retrofitted to a DIY LDR shunt volume control. I made the modification to an AtmaSphere MP-1 balanced preamp and am pleased with the improvement.

I believe the only commercial preamps with LDR controls were the top Melos models of the late '90s and current darTZeel.

Commercial use in an active preamp is problematic insofar as even closely-matched LDRs don't track each other very closely above 15K. L/R channel balance shifts with changes in volume. This doesn't bother me, but may test the patience of a couch potato.

4v? Wow, I have never heard of any amp that was over 2.5v.

Shakey

Nguyen787,
Higher Input sensitivity means a lower number. For example a 1V sensitivity is better than 2V. A 700mV sensitivity is better than 1V. Gain was exactly the reason I chose the Parasound A21 over others, when using my TVC which is a passive component.