Bat VK-P10 and Sonic Frontiers SFP 1 Signature

No wonder. I sold my VK50SE long time ago.
You should try the NEW Sonic Frontiers Phono 1 SE.
I'm very happy with this preamp. Good luck

i heard from different people that bat mates good with only bat.
some cases i believe are true.

is there two sets of inputs/outputs balanced/unbalanced?

if yes you should only use balanced connection and newtralize the unbalanced with cardas caps available at needledoctor.com. inverting polarity might also help as well.

in general very few all-tube phono stages have low noise floor and it's upto the consumer to judge wich ones are the best-suitable.

i possess arc ph3 that is as you might know has hybrid designe with driving sovtek 6692 and mosfets on the output.

as a rule of thumb the input sencitivity of phono preamp is higher on balanced inputs than on un-balanced and so the s/n ratio is higher.

it's ok to use adapters(Neutrik RCA-XLR pro-grade is OK Cardas is certainly better but$$).