Generally, you can use a 12AU7 or 12AT7 in place of a 12AX7 without fear of harming your preamp, as they are electrical similar but the U7 and T7 have lower gain. That doesn't mean it will sound the same; it might be better, it might be worse. Checking with YS Audio first is always the safest bet.
I have a Jolida JD9 that will use all three, and with MM cartridges I prefer the 12AT7 over the stock 12AX7. The 12AU7 just doesn't sound right regardless of cartridge.
I have a Jolida JD9 that will use all three, and with MM cartridges I prefer the 12AT7 over the stock 12AX7. The 12AU7 just doesn't sound right regardless of cartridge.