How do you test for this ?
Do you open the gain knob without any mic connected ?

Mic is of course connected. Mic has its own noise of course, namely 15db as per manufacturer but preamp adds too much noise after +30. That's why i have to later boost each recording by 15db manually by multiband expander in a noiseless manner after weakening noise in sound editor using recorded noise for profile. I wonder how they get clean and load recordings. Btw the built in mic  in panasonic gs400 dv camera records loudly and cleanly, almost scientifically razor clean. Some years ago guys from a diy forum were buying same or similar panasonic capsules for diy mics. What i want to say is that loud noiseless recordings are possible even with some cheapest preamps and capsules. But i don't see anything like those in the market for musicians...

Is there any RME gear involved here? What kind of mic are you using?

I record into hammerfall's inputs.

The topic is about preamp. Anyway, i use multiface nuendo steinberg hdsp with inputs' selfnoise at -90db as per hdspmixer's meters. I remember in 1999 we recorded loudly and cleanly with plastic electret genius 5 usd mic plugged into some cheap pc soundcard with no peamps involved. Now with rock solid metal cased bm800 and preamp i get noise. Without ionizer dx plugin it would be impossible to do any recording. It's real savior to boost signal without boosting noise.

The card is working well, i am pleased to have acquired it. And right, it has no preamps. Right, white noise is observed with delta1010lt and audigy2 also and it's much louder (-72 vs -90db input selfnoise) than noise obtained via hammerfall. Btw audigy2 is usable on linux and cleaner than that delta1010lt. I was astonished to find out it can record smth as on windows xp kxdriver it had been noisy and too quiet as hell. We have 2 pin receptacles here in our houses, no 3rd ground. But i suspect that it's mic and preamp who are to blame. If we think it over logically with 60db amplification all should be amped, noise both with instrument's signal and that signal should mask noise but that does not happen which indicates that audiobuddy starts giving noise at amplification over +30. But even if staying within +30db i have to clean noise, use gated boost by ionizer to get some highs. It's all painstaking.

Input selfnoise means noise shown in hdspmixer or daw track with monitoring ON when nothing is plugged into input. This noise happens inside card, not from preamp, not from mic.

Every preamp creates a lot of noise when nothing is connected.
You have to connect a mic or a dummy plug to make a test.