Can you mix string brands if they’re in the same gauge? I have Ernie Ball strings and the ‘A’ string broke. Was wondering if i could Replace with a fender string of the same gauge?
There is no fundamental reason to use a single brand or even a single weight from one brand for all strings. Granted you may find it easier to maintain an even sound level and strum/pick force if all strings are in the same weight class, but especially for acoustic guitars, you might find that swapping in one or two different weights improves the tone balance.
By way of comparison, many cellists use different brands and weights for the upper two strings vs. the lower two.