220K vs. 470K mix resistors ?

[floyd]

How would using 470K channel mix resistors instead of 220K affect tone in , for instance , an AB763 circuit ?

[tubeswell]

470k resistors would decrease the AC load on the previous stage(s) compared to 270k resistors (by increasing the resistance to ground on the 'passive' side/channel that is feeding into the mixing resistors). This results in marginally less signal attenuation, but marginally more S/N noise.

[HotBluePlates]

If there are coupling caps in series with them, it will also shift the roll-off point downward.

That said, the values are generally chosen due to other circuit values, so it doesn't really benefit you to tinker them.