From my understanding of the tube data sheet I found, the only difference on paper between the 12SN7 and 6SN7 tubes is the heater voltage. From a practical standpoint, the 6SN7 are much more expensive, which led to my query.
What are the subjective differences between the two tubes when used as the input and output tubes of a preamp? They'd be going in my Aikido Octal preamp, which has the capability to be set up for either tube type.
Any 12SN7 to look for specifically?