@mulveling oops. Thanks for the correction. That’s embarrassing. I always assumed Hagerman was a genius for pulling that off without FETs and using 6 tubes instead of the usual 3 in MM amps. Ah well...
@noromance Clever as Hagerman is, all-tube MC amplification to 70dB+ is simply going to involve a good bit of noise, and lots of stress over tube selection! Aesthetix is the only brand I’ve seen attempt that, and I don’t have experience with them to share.
I believe the extra tubes (4x 12AX7) are for balanced circuitry in the RIAA stage. Older Trumpets also had a balanced output stage topology (4x 12au7), and the original Trumpet could be optionally ordered with XLR ins/outs - though very few were made this way, for some reason (probably, there were fewer preamps with XLRs back then!).
And no worries I’ve made lots of mistakes and misspeaks over the years - fortunately this is a forum for audio opinions & experiences, not a scientific journal :)
Electrostatic "direct drive" headphone amplifiers share a similar need for massive gain - usually 60dB - and most of them have a FET front-end for most of their gain. There are only a couple exceptions. I’ve used this on a vinyl source and it’s kind of mind blowing to think about the 120+ dB of total gain from stylus to headphone stators in these cases, and how it works AT ALL, much less how well it does.