In a classic case of curiosity killed the credit card, I just got the base today as well. Lately I have been having a real moment with the Chord Mojo 2, and I haven’t been listening to the Tube Mini as much lately. I was prepared to be pretty underwhelmed by the base. Just putting that all out there to say that my mindset was actually predisposed to be negative. I listened to a couple of albums while doing paperwork this evening - Pronounced Lynyrd Skynrd that I ripped in DSF from MoFi SACD and Norah Jones Come Away With Me 192/24 from Qobuz. Headphones were Atrium Open through single-ended output, but I switched for a couple of tracks to the Focal OG to try it out on the balanced output. I have to say at first it seemed nice, but nothing too out of this world. Multiple times, however, I was pulled out of the paperwork by some detail I hadn’t previously noticed. I had a sense from memory that transients, particularly on low frequency instruments like bass drums and bass guitars were better defined. The tonal richness I had noted with the Mini before is about the same. When I switched back to using the supplied USB C->A cable, I was surprised at the difference. The soundstage became more intimate and flat. I was also surprised at the fuzzy / static edge that was added to the vocals, and I confirmed that this went away again with switching back to the base. The overall detail level was very noticeably lower on these well-mastered tracks without the base.
Regarding the background hiss, I didn’t hear it with the Atrium with or without the base - I think the SE output is a bit less prone to the hiss, as are higher impedance headphones. The Clear OG had been the biggest offenders for the hiss of any headphone I have tried. Hooked to my iPhone directly and listening through the balanced output, the hiss is absolutely noticeable when the music is paused, though I will say it has decreased over time quite a bit as the tubes have broken in. Using the base, it is difficult to describe. The hiss wasn’t exactly audible, but it was like I could tell something was there when the music was paused. It is a marked improvement in the hiss to the point where it is barely noticeable or even identifiable as hiss in the worst case scenario headphone from my collection. Honestly, if the level of hiss present with the base attached is bothersome to someone, tubes are probably just not a good fit for them, full stop.
Also worth noting, using the base was markedly improved relative to my improvised setup with a high-output (up to 100W) power bank plus iPhone connected through Topping HS02 from a few pages back. I am not sure if the base has some software component that tells the Mini to use more power, or if there is just inadequate isolation from the HS02 + battery, or maybe the battery I was using is noisy, or maybe it is just the ultra stability provided by this thing. The base is a tank and has a much heavier, high-quality feel than I anticipated.
I have mentioned before that I really don’t tend to like Sabre DACs as a rule. My Matrix Audio X-Sabre Pro MQA drove me insane with a sense of grit no matter what settings I used, even through my very smooth tube pre and tube amp on my speaker system and my WA22, and I sold it at a major loss. I have found a number of other Sabre-based DACs fatiguing and sold them off (the Dragonfly Cobalt was okay, but I just think other options sound better to me). I was worried that it might be a poison pill in the Mini before getting it, but this one is executed exquisitely, and I really enjoy listening to it even without the base. I think it just takes all the edges off, even some that weren’t bothering me before. It just sounds more refined with the base.
In any case, the base is a notable improvement, and I’m surprised to be saying that. I actually saved the box and didn’t unwrap all the little accessories, as I was thinking I was going to end up putting it on EBay as a pair and going with the Mojo 2 as my exclusive portable setup. This is no longer the case, and I think I’ll be keeping it around (along with the Mojo 2, which I am still just blown away by). I may do some direct comparison of those if anyone is interested. As with all things, the law of diminishing returns applies, and while I feel like a base and a stand seem steep at $300, looking at it the other way around, I can absolutely see how the combo is competitive with an $800 DAC/amp. I think if you listen to the Mini with it for an hour and then switch to plugging it straight into a device, it will be hard to ignore the improvement…