I have the FX AUDIO T03 and the AIYIMA A3 Tube preamps and they sound very good. Also have the AIYIMA T9 Bluetooth Tube preamp. I don't recommend the T9, it is flawed. They are all upgadable by changing the NE5532P OPAMPS to better Texas Instruments
I Have the FX AUDIO T03 and the AIYIMA A3...