Audio Research Reference 3 and BAT spec 6H30

77jovian, I would start with the preamp there will be a noticable difference. The LS-26 is a great preamp and deserves the DR's but eventually you will have to do the amp as well as you'll be craving what the total DR's in your system can do.

I only have experience comparing NOS 6H30DR to new- production Sovtek 6H30 in a VK75SE. In that amp there is only minor improvement with DR, which diminishes as the tube ages. In my amp a fresh Sovtek surpassed a DR after about 1500 hours of use. Do the math and decide. Though a tube may survive for 10K hours, its gradual degredation in performance will vary by application.

In the 6H30 iteration of the APL Denon 3910, there was not any appreciable
difference between 6H30 and 6H30DR, IMO.

Agree with Dgarretson regarding the 6H30 in the VK75SE. BAT no longer supplies the DR tube as standard even in the REX where 8 are needed. Prices of the DR will only continue to rise as the supply falls.