Can preamp tubes be replaced individually?

[imc2111]

Tube amp newbie here.. Heard that power tubes should be replaced in pairs (correct me if wrong), what's the deal with preamp tubes? Is it ok to replace individually?

 

[Jackie]

No, preamp tubes don't need to be matched, nor do you have to adjust any voltage or watch for any ratings. Just pop it in, that's it. Make sure it's a 12AX7 or ECC83 (same thing, different name, the former is US, the latter European) though. If you use for example a 12AT7 or 12AU7 (aka ECC82 and ECC81), you might get a thin sound, or lower gain.