Kind of expected because:
1) the specialized damper diode rectifiers have very soft switching compared to solid-state diodes, thus much less 50/60 Hz switching noise radiated into the rest of the circuit and out the AC power cord
2) the regulated high voltage B+ power supplies have an astounding 130 dB of noise rejection from AC line noise
3) there is an another layer of VR-tube shunt regulation for the B+ power of each channel, good for about 20 to 30 dB of added isolation
4) All heaters are fed with 6.3 volts of regulated DC
5) last but not least, balanced operation of the 6SN7 circuit provides an additional 30 to 35 dB of noise and distortion rejection, without requiring feedback.
That’s why the Raven (and Blackbird) cost a bit more than other preamps and power amps. Each Blackbird power amp does all this rigamarole three times, with KT88 and 300B power tubes, which is why it’s priced where it is.