BAT Vk-51 SE vs Aesthetix Calypso

Does the Calypso challenge the big BAT dynamically and in low end heft and extension ? Has anybody had the chance to compare these in the same system?
I expect the BAT is at another level but have heard raves about the Calypso by Michael Fremer and Robert Harley.
Opinions please! And thanks !
Bill, In addition to better bass, you will also get a lower noise floor with the BAT. This equates to better low level detail. Both freq extremes will be better. Fremer and Harley rave about both, go figure...
I had the VK-31se and the Calypso here at the same time for 2-3 weeks to compare. Even with the lower model 31se the BAT was nicer than the Calypso, with equal detail, more weight, better and deeper bass, and most of all MUCH quieter.
I had the 51SE then downsized somewhat and had the Calypso, everthing else in the system was the same at the time.

I thougth the Calypso was a very nice preamp but not in the same league as the BAT. The BAT was quieter and had more of the dynamics and heft you mentioned. To me it just sounded more natural.

I don't think the comparision is fair to the Calypso as the retail price of the BAT was twice the cost. I think here you get into that area of diminishing returns. To me the BAT wasn't "twice" as nice as the Calypso but in my system and in my opinion it was a much better preamp.

You may want to seek the signature version of the Calypso.
I forgot to mention that all of my listening with the 51SE was with 6H30-DR supertube. That was the standard tube in the preamp at that time.. As you probably know those are more scarce now.
I don't know much about the Calypso but I own a BAT VK50SE and later a VK51SE for 9 years. IMHO, the BAT sounds closer to a solid state than to a tube. Please beware of that when you make decision.
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Speaking with unabashed bias for the Calypso which I currently own... I have found tube rolling makes a huge difference in the performance of this preamp. My only experience with BAT preamps was with an entry level VK 30 and I was not impressed, so sold it and upgraded to a Joule Electra LA 150. However, I've heard nothing but good things about BAT's VK 50 series pre's, so my comparison to the VK 30 holds little relevance.
A few thoughts from a BAT and Aesthetix user: I prefer the BAT non-SE equipment because you can roll tubes. Perhaps Sidssp's experience of BAT gear seeming more like transister gear comes from using the SE versions. With the BAT VK31 I put in Amperex bugle boys and was quite pleased--a good platform for NOS tubes. With the VK75 I put in a couple of CBS Zylicron (sp?) from Upscale Audio, which had a nice warming effect.

I have an Aesthetix Rhea phonostage and, frankly, I don't like it. It uses Sovtex tubes, and I think that is the problem. I'm looking to do some tube rolling in it, but in reading the reports on Audiogon, it sounds like a rather complex undertaking. But, we'll see.

Granted, I'm comparing apples and oranges somewhat here, but out of the box, I preferred that BAT gear to the Rhea. Yet tube rolling can change those more experienced than I can attest to in more detail.
I chose to keep the Lamm LL2 in a head to head comparison in my system vs. the VK51SE (I owned both at the same time). I did not really care too much for the Calypso, but owned it before the other two. I believe I chose a VTL 5.5 over the Calypso, then subsequently a Tom Evans Vibe and Pulse Lithos 7. The Lamm sounds sort of similar to the Vibe, but with better bass, dynamics, clarity and top end. However, the Lamm has nowhere near the ergonomic features as the BAT or Calypso. To answer your question, based on my recollection, I would choose the VK51SE over the Calypso.
While I am partial to NAT Audio since my firm also imports the line, I would like to suggest doing some research on Plasma R or the Symmetrical preamps which will easily outperform the linestages mentioned above and the Plasma R has 10 tubes inside while the Symmetrical is configured with 12 tubes. and

Good luck