The caveat comes from the fact that the system without Thunderbird leaned to the overly analytical and bleached side of things. I wondered whether the fact that the combination brought back balance did not imply that the Thunderbird itself leaned generously and maybe excessively toward the plushier and meatier side of things. To test my theory, I borrowed a First Watt SIT2 for a day. The much lower-powered and higher output impedance SIT2 is an almost perfect transistor stand-in for the triodes I so much enjoy and is slightly warmer and somewhat looser than the F5, without the upper midrange bite that can turn the F5 whitish at times. When pairing the SIT2 to the Thunderbird, my assumptions confirmed immediately. Pace slowed, bass got looser and the upper midrange closed in. It was still a beautiful presentation, even more tonally intense and rich but clearly turning to liquid chocolate syrup with its ponderous implications. I even tried to run the Thunderbird into my 2A3 integrated. This resulted in an even looser more euphonic presentation very much like a vintage 300B - bloated and slow, characteristics that could not be further from describing the stock Triode Lab amplifier. Towards the end of the review, the LampizatOr Golden Atlantic DAC made its system debut and it too leaned towards a beautifully intense tonal color, thus making it an imperfect mate for the Thunderbird. Keep it lean before and after is all I can say about ideal partners for that bird. It sings with strength and gravitas but don't expect a hummingbird any time soon.

Point made, the Thunderbird is a sublime remedy for systems in search of soul and substance but can easily turn to excess in systems that are balanced or already voiced on the more luscious end of the spectrum like mine. More of the same could be said of the MM phono section. MM carts are typically more beefy and tonally dense than their MC counterparts. Although my Dynavector 10X5 mk4 is a high-output moving coil, its sonic profile is very much MM-like with very dense tone. Played through the Thunderbird, density and weight jumped up another level versus playing the 10X5 through the solid-state Lounge Audio LCR, like a generous helping of heavy cream thrown into chocolate sauce. I wouldn't describe the Lounge LCR as lean for a solid-state phono preamp. It is nicely balanced and extended without excess stiffness but compared to the MM phonostage in the Thunderbird, the Lounge provided nicer illumination and greater separation of instruments. The Thunderbird was not opaque or slow per se—midrange resolution was actually quite stunning—but overall tonal density was pushed farther than natural and that's how I felt about the 10x5/Thunderbird combo. I had to pull the Ocellia pure silver interconnects back into service instead of the Zu Varial to return some light to the picture. Even then it was still a highly saturated image

When I switched to the Ortofon Quintet Black moving coil cartridge using the S.A.Lab step-up transformer into the Thunderbird, things went back to a more central tonal balance although still on the richer slower side of neutral. At the same time as pace slowed down compared to the Lounge LCR and Copla combo, transients using the Thunderbird phono rounded and listening to music felt like settling into a deep cushy couch. The contrast to my Genesis Phono Gold could not have been starker. The Genesis is a speed and resolution demon with magnificent extension yet the most natural-sounding tone I have heard to date in a phono preamp. Conversely, three layers of cushy dynamic behaviour from the full S.A.Lab complement proved just too much comfort even for me. Just like I am not a fan of the full-on vintage 300B aesthetic, I could not get emotionally invested in the full S.A.Lab Monty of Thunderbird and step-up transformer which in many ways managed to turn the spicy First Watt F5 into a NOS Western Electric. On the other hand, the hyper-caffeinated Genesis Gold run into the Thunderbird and F5 sounded positively gorgeous, the tubed preamp managing the fine balance of adding color and soul without killing dynamic drive. I am not an electronics designer but it certainly felt that one tube stage did the trick but three was massive overkill. That said, as a tube preamp sitting between a lean DAC or phono stage and a lean amplifier, the Thunderbird completely took me by surprise and delivered a superb rebalancing act which turned a bleached combo into the most synergistic tube and solid-state association I have had in my system so far.

All this to say that in the right context and with the right expectations, the Thunderbird can be a very powerful tonal enhancer which delivers an enticing blend of transparency and tonal richness with weight and drive. Really good care must simply be taken in component matching to not turn too much of a good thing to excess. Regarding the phono section, I would look for open and dynamic cartridges beyond my denuded Quintet Black and experiment with solid-state step-up preamplifiers to try and strike a more dynamic balance than what can be achieved with S.A.Lab’s own passive step-up. As always, context in audio is everything. What I found at times excessive in my already tone-rich system will be the perfect fit in another system in need of a color injection.

S.A.Lab website