Looking for 5AR4 rectifier tube most like solid state

The sonic signature of your preamp is mostly the 6SN7 tubes. Voltage sag is not an issue (I think) because those tubes maybe draw 5mA each idle and maybe swing to 10mA on full signal. So the highest plate current is about 80mA for all 8 tubes which you do not hit unless playing full volume.

The 5AR4 drops the least amount of voltage for a given plate current than other standard issue rectifiers. At that plate current it's only about 5 volts, which should not really affect the linearity of the 6SN7 tubes. Rectifiers are more carefully chosen for power amplifiers, but in preamps I don't think will make much of a difference.

Another different take, or perhaps in addition to....have you done much tube rolling with the preamp tubes?  They can be quite different from one to the next.  

@danager +1 on the space tech lab super rectifier, I own one and it makes a profound difference with my preamp. I don't know exactly why it makes such a difference, but it does, if I want it to sound more like solid state I just roll in a couple 3B22 or 3B28 tubes, if I want more tube sound I just use 300b or 2a3.

I have the Cary SLP05 with ultimate upgrade as well but don’t suffer what you are describing. I find that the Raytheon VT231’s in the gain stages gives the best sense of best solidity. To be honest, I have struggled with understanding this rhythm and pace issue outside of turntables. I have had a number of preamps over the years, tubed and solid state, and feel the Cary is not slow in comparison (recently have had Audio Research and Schiit preamps as well).

Sorry, base solidity