Guido,
IME monolithic op amps can sound great on batteries-- perhaps surpassing tubes-- but if that preamp has anything short of magnificent bass control & dynamic authority, you can likely blame choice of NiMH batteries.
IME monolithic op amps can sound great on batteries-- perhaps surpassing tubes-- but if that preamp has anything short of magnificent bass control & dynamic authority, you can likely blame choice of NiMH batteries.