Tuning by ear is the way to go here, as others have said. 10x the internal resistance of the cartridge puts you on the edge of pinching the signal - that is decreasing the volume by resistance instead decreasing it by lowering the gain. Once you get down to 5x, this is noticeable. Downstream volume pots can be opened up if you pinch the signal at the phono pre, which may be preferable. I’ve always thought most systems have too much gain. Some carts I have (Miyajima Zero and Denon 103R) sound better to me when pinched at the phono pre. Some (Hana) are the opposite and sound better opened up. The differences are subtle and in my system come down to bloom vs transients - or to say it another way - fullness of the instruments vs separation of the instruments. When the resistance is pinched, tones fill up with more bloom. When opened up, instruments have more space between them. I’ve tried recording A/B to DSD and then compared playback - that didn’t work. Best to work from a recording you are very familiar with.
