I spent some time with mine. I’m coming from a PAX, running a passive P and J bass into any on my amps; Fender Rumble 500c, GB SM 9.2, GB STL 900, Ashdown LB30, and Fender Super Bassman.
UA plays well with all my amps. The PAX didn’t play well with the OD of the rumble and was a bit noisier through my all tube amps.
I feel that UA is a step above in every aspect of my PAX. The gain knob does exactly what I want it to do, ranging from clean to full on OD. I like just a tad bit of hair when I dig in, like the old 70’s rock bass recordings. It handles dynamics well in this regard, and I can dial in a nice fat bottom with prominent mids and an ever present top end that is clear and smooth.
I still love my PAX but the UA really is the pinnacle of tube preamps IMO. Great price, quality build, killer sound, and looks freaking awesome.
@Sushi Box FX
You really hit the nail on the head with this pedal. I am going to be doing an out of state gig next week and can’t wait to flow the golden tones of this box out to the PA into the crowds ears.
Full disclosure; I’ve been at this for a long time and people reading this might think it is a “honeymoon” phase, but I buy, test and gig gear enough to know what is up and what will work for me. This killer little box is incredibly useful for us tube lovers.