I agree with the comments about loading, but... understand it is a very modestly designed unit using op amps with a switching wall wart power supply.So I unhooked the preamp for good. It was producing a sound too hot for me. Now things are smooth and warm again, not amplified and pumped up on both ends. I don’t mind having the volune level a bit lower... it will never match the aux level output.
"Audiophile grade" as screened on the cover it is not.