I have a pair of the 300b-z that I am running in in a Manley neo preamp. These are "grey market" i.e. they are not the premium tubes from Grant Fidelity. They have matched plate current of 37mA, which is below the Grant acceptable select values of 48mA to 70mA.
Already, without significant break in, they are better than EH gold grid, Svetlana, TJ mesh gold pin, or JJ's.
I would say initially that the difference is "weight" and "balance". Density but with delicacy, and excellent soundstaging. I will make more observations as they run in, I guess it is expected that they will be a little goose-ey at times until they reach their recommended break in of 300 hours.
Already, without significant break in, they are better than EH gold grid, Svetlana, TJ mesh gold pin, or JJ's.
I would say initially that the difference is "weight" and "balance". Density but with delicacy, and excellent soundstaging. I will make more observations as they run in, I guess it is expected that they will be a little goose-ey at times until they reach their recommended break in of 300 hours.