I wanted to followup with many compliments to Backert Labs on the exquisite Rhumba Extreme.
I had the pleasure of using this preamp with Pass Labs X150.8, the direct input of my Audia Flight FLS10, and PS Audio M1200 amplifiers, with sources including the EMM Labs DAC2x v2 and a T+A G2000R turntable (built-in phono stage; I know, its sacrilege... but it's really good). My comparison was the LTA Microzotl L2 preamplifier using 12AU7 drivers to diminish gain.
Into the Audia Flight, both the Backert and Microzotl, had issues driving into a 7.5kohm input load. No surprises there, hence my listening quickly switched over to the Pass and PS Audio amplifiers. Where both proved dead silent, and extended at both extremes (read: no capacitance, impedance, or gain issues whatsoever... nada). My impressions derive from a combination of both amps.
Whereas the Microzotl consistently produced tighter and faster bass, and a more explicitly layered soundstage with a layer of warmth most clearly felt around the upper midband, the Backert's tube addition was most felt at the upper bass and in the mid-treble... in my system, this is a good thing. Without over smoothing the mids or shipping microdetail, the Backert imparted a modicum of welcome tube warmth to bass and a hyper detailed, realistically scaled cymbal sound on well-recorded jazz and rock albums. The midband was a consistent delight with true nuance and palpability.
For most music I auditioned, the Backert would be my first choice. The LTA countered with a touch more control on orchestral tympani and with precise depth layering of electronic music. Also, channel balance was preserved with the LTA even into the very, very lowest volumes, it's nice to have a balance control and input switching from the remote, and the LTA apparently includes a superb headphone output (which I did not audition in my system, but have heard elsewhere).
I ultimately felt the Backert's dynamics, richness of tone without loss of textural nuance, and timbral naturalism in the all-important midrange, made it the stand-alone preamplifier to beat. All the grace and beauty of the best tube sound, with no real notable aberrance or sense of drowning in artificial harmonic sweetening. Highly recommended.
Even still, I ultimately elected to convey the separates to other parties and stick with my Audia Flight FLS10 as it is at once a) hard to sell locally (which is a requirement for me with such a heavy unit and without wanting to deal with freight), and is ultimately just a little more see-through than any of the above combinations. So convenience and quality, in a nutshell. The precision of tone (you'll hear sibilance when it's there), detail (every tape splice), bass that is both the densest ball of energy and yet a bit dry, and staging (smaller images in an endlessly unbounded stage) is definitely a warts-and-all-approach - but it gets me a little closer to the very best recordings and rewards the sheer electrostatic like speed and phase coherence of my GP omnipole speakers with their largely wideband bending mode radiation based omnidirectional wave launch. In a horn or otherwise varied system that prioritizes alternative qualities, I can see a Backert line stage being a very clear preference. Incidentally, the preamp stage of the Audia FLS10 is pretty much equivalent to the FLS1 recently reviewed by Stereophile (where Fremer gives us a nonsense comparison to some Dartzeel pre he owns).
Were it possible, I'd have kept the Backert in a second, all tube system... it's very tempting!
