BAT or Pass With My Sophia 2s?

Consider Madfloyd has not yet paired his Pass Labs XA-100.5 with a preamp that matches optimally (the preamps he used both have high output impedances that are too high for the Pass Labs amp). This is based on his comments in another thread.

So, take his recommendation here with a degree of caution.

From a thread discussing Pass Labs XA-30.5.

06-13-10: Madfloyd
I haven't had good experience driving the Pass with tube preamps. I've tried the Cary SLP-05 and the Audio Valve Eclipse and the low bass is rolled off. It's one of the reasons I got the Bat.

Both the Cary SLP-05 and Audio Valve Eclipse have output impedances that rise to 3400 ohms and 3090 ohms at 20Hz. Not good when matching with an amplifier having an input impedance of 20k ohms/30 k ohms (single ended/balanced) as does the Pass Labs XA-.5 series.

Match a tube preamp with a low output impedance (below 300 ohms, IMO), and you will have an excellent match with Pass Labs XA-.5 series amps.