David,
I suspect you ran into the difficulty I mentioned, that the F4 requires a very large voltage drive to achieve full power. This is a separate issue from gain. Some preamps are capable of outputting the voltage necessary; some aren't.
I suspect you ran into the difficulty I mentioned, that the F4 requires a very large voltage drive to achieve full power. This is a separate issue from gain. Some preamps are capable of outputting the voltage necessary; some aren't.