Being the importer for Einstein Audio in North America, I have tested the original Einstein preamp with the MKII Version for several months on a highly resolving system which includes the Acapella Triolon speakers. The difference is not subtle! What I noticed most is that the MKII Version is more open sounding, has more resolution and sounds more refined. Consider this; Einstein would not have changed the model to MKII if the improvements were not clearly audible.
As for tube rolling, There is no need to change the stock tubes for the power supply. In fact the power supply tubes have little or no effect on the sound. The input tubes are a different story! I have tested many tubes here, and I found the best are the Telefunken Cca gold pin, and the Philips ECC88 gold pin from 1960. One of the benefits of this preamp is that you can run different input tubes for each input, which allow you to taylor the sound of each input to your source. My experience with tube rolling on the Einstein preamp's input is stay with high resolution type tubes that are low coloration and ultra quiet, since this preamps strength is like live music, and if you use a dark or colored sounding tube this will take away the preamps best qualities.
Best Regards, Brian
As for tube rolling, There is no need to change the stock tubes for the power supply. In fact the power supply tubes have little or no effect on the sound. The input tubes are a different story! I have tested many tubes here, and I found the best are the Telefunken Cca gold pin, and the Philips ECC88 gold pin from 1960. One of the benefits of this preamp is that you can run different input tubes for each input, which allow you to taylor the sound of each input to your source. My experience with tube rolling on the Einstein preamp's input is stay with high resolution type tubes that are low coloration and ultra quiet, since this preamps strength is like live music, and if you use a dark or colored sounding tube this will take away the preamps best qualities.
Best Regards, Brian