What can you tell me about First Sound pre-amps?

Yikes! Rackon is correct, I do mean finer increments. I always thought this was an appropriate use of granular, but I just went to the dictionary and see that I'm all wet (or liquid, if you prefer). More steps in the stepped attentuator, how's that? (Not to be confused with having a preamp that goes to 11, which is also a good thing.)

Drubin, I agree. It's interesting to note that the steps in the FS Holcro
attenuator are not an issue when I run my VAC Phi 110/110 with
negative global feedback, but it does become an issue when I run the
amp with zero global feedback...especially at the lower volume steps (1-
3). I notice a big jump in volume between positions 2 and 3 on the
volume pot.

Kalan, regarding downsizing, I think if I had the dough, and the proper
motivation to take the plunge, I'd buy a VAC Phi Beta integrated amp. It
wouldn't be downsizing from a cost perspective, but it'd be downsizing
from a two to one box solution with the benefits of ideal synergy
betweeen preamp and amp, and the obvious elimination of a set of
interconnects and a power cord.

Rackon:

It's possible that the FS and the Valhalla aren't the best of friends, but in this system, it does show up regardless of the interconnects.
Trust me, Artg, I'd love nothing better than for the system to NOT sound a bit hard on brass crescendos. I just don't know what else I could change as every single components, tubes included, has been substituted into the system. It's a bit of a puzzle to me. I wondered if the OA 2 tubes could be going bad, as they're the only tubes I HAVEN'T changed in the preamp!
And, for those considering the First Sound, it is entirely possible that this may be an issue endemic only to MY particular preamp. Not this model, just, literally, the First Sound Presence that I own. And I've read the reviews and I've never noticed anyone mentioning this. Unfortunately, my First Sound hasn't read the reviews, and it seems not to know it shouldn't sound edgy on Forte-level brass!

Mphkns, Here is another hypothesis: is it possible that what you are hearing with FS on loud brass creschendo is what is sometimes called 'cuivre', or 'brassy', which can be heard live, when the metal body of the horn actually vibrates somewhat loosely under extreme FFF. If that were the case it may mean simply that FS is more revealing than other pres. But, if you do not like 'cuivre', you are not the only one. Cuivre sound is the bane of orchestras and conductors, unless it is specified explicitly in the score.

My understanding is that the OA2 tubes are either good or they are not, but they don't go bad over time. Also, as I recently discovered, the preamp works just fine even after they do go bad (or at least after one goes bad). The triode tube doesn't get properly biased is all that happens, so you may start to notice some sonic changes.

By the way, I bought 4 of them from New Sensor and it's a good thing because one of them failed pretty much right away. Apparently the failure rate is high, but if it happens, it's within a couple of days.