According to an old Radio Amateur's Handbook, gain factors for 12A*7 tubes are as follows:Stratin2traynor said:I was just curious to see if switching up to 12AY7's (I think these are supposed to be higher gain) or down to 12AT7's would make much of a difference.
12AT7 - 60
12AU7A - 19.5
12AV7 - 37
12AX7A - 100
12AY7 - 40
12AZ7A - 60
In other words, a 12AX7A gives the highest gain for a preamp. Tonal as well as build quality depend on the manufacturer these days. Hope that helps a bit.