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

Guidocorona, thanks for the suggestion that this might be what I'm hearing.
I suppose it's possible. It's just that it seems unlikely that it would show up on nearly every cd in the collection, especially given that I've had some of these cds since 1991, and have never heard this particular sonic trait before, and I've had some very revealing equipment in the "good ol' days." If it only showed up on several of the CDs, I would just chalk it up to the CDs themselves, but it appears pretty frequently. The oddest trait is how it's ONLY brass that causes this effect. I suppose it's still possible that the First Sound is showing this, but over the course of 20 years, I wouldn't think that the First Sound is the first high resolution preamp to demonstrate this.
In any case, I'm more interested in doing the detective work to find out what's causing it than getting another preamp.

That was going to be my next suggestion, but TVAD beat me to it. Emmanuel will be on vacation until April 20th, after which we can ask him about the possible nepherious effect of Holco resistors on the brittle brightness of brashingly brassy brass, the moral philosophy of dual unstacked stepped attenuators, and other such esoteric matters.
In the meantime, replacing Gabrieli on modern brass with Gabrieli on sackbuts, ebony and rosewood cornettes, serpents and pendulous serpentones may alleviate your suffering and prevent all cavity fillings from shattering prematurely 'in situ'!

I'm sure Mr.Go has his reasons for making the preamp with dual volume controls. Whether or not anyone thinks they are valid or not will probably not change his mind or make him say, "Gee that's a good idea. Why didn't I think about that?"

well, well, well, here's a gem for the taking....

http://cls.audiogon.com/cgi-bin/cls.pl?preatube&1118799988