Which one...

I have not heard the M2x. I've always been interested in building one though. I was surprised at how good Wayne's linestage is, and there is something I like about having some signal iron in there. I don't know what it is though... maybe a small amount of "pleasing" distortion without being too warm and gooey??? Just not sure. I use the balanced input option on the BA 2018. So it also serves as my balanced to SE converter. I power it with a killer PS, the Salas designed Ultra-Bib shunt reg and an overkill toroid.

I don't think you will find M2 too warm and gooey. While it surprised me greatly to learn it has a bit more 3rd order distortion than some other of the First Watt amps, I did still find it warm compared to F5 or F6.

Great sounding amp.

Russellc
 
It is the BA-3 Pre (preamp for BA-3 power amp) that has P3 to adjust distortion.
Oh okay... thanks. I am going to build the UGS Muses V2 (custom Salas shunt regulator PSU) no matter power amps, but the BA-3 amplifier sounds interesting, but so does the balanced version of the F-4 - both are current gain only so should theoretically sound better than an amplifier which has both voltage and current gain... so much to discover... he he