Compared to the BT30D non-Pro, the Pro version is quite a bit longer and heavier (430g vs 620g).The knobs are made of aluminium, different texture compared to the no-pro, a bit more resistance to turn than the. Same throw switch used to power on.The 3.5mm PRE OUT is full range.Bluetooth will be always-ON so your neighbor can hijack your device just like the non-pro version. Remove the antenna to prevent this from happening if you don’t use BT. Come on Fosi Audio, please fix this.The amp has a 4” tall BT antenna, again it's better than the 7” incher of the DA2120C that looks like a CB radio... Please give us the 1 incher for future products, for once the smaller the better.BT uses an ATS2853 chip that is also found on the BL20A.How does it sound?I did a comparison with Onkyo RZ50 pure output mode (airplay), Aiyima T9 (BT), and the BT30D non-Pro (BT). All using RP5000F towers, with an amp selector switch.Right away there’s a BIG difference between the non-Pro and the rest.The Pro version is much more dynamic, the voices are clearer, bass is more present and punch harder.I honestly cannot tell any audible difference between the RZ50 and the BT30D Pro. The T9 sounds only a tad warmer (thx lamp); Even that it was really hard to tell and it depends on the song being played.The Pro version sounds definitely better than the non-Pro.To test the passive sub output, I hooked up my gutted Z2300 logitech subwoofer, it works wonderfully and has a very capable output. However, I didn't like the sub crossover control, the adjustment doesn't feel linear. There are no frequency indications on the knob, it can only be tuned by ears.The muscle: TPA3255 x 2:PSU idle voltage: 32.3VPower adapter output @ 8ohm load current and voltage, 125W:Same 32V5A adapter used for multiple models. No sparks occurred while plugging in the DC plug compared to the DA2120C I've tested, I made multiple attempts to make sure this is repeatable.Here I am trying to figure out the max usable volume before getting a bad shaped sine wave, The volume knob is at 3 o'clock, BT reference volume maxed out on my mobile device, no EQ, no tone.L & R Channel, 8 Ohm load, 1000hz tone, 26Wrms per channelL & R Channel, 8 Ohm load, 1000hz tone, clipping at 60WrmsL & R Channel, 4 Ohm load, 1000hz tone, 40Wrms per channelL & R Channel, 4 Ohm load, 1000hz tone, clipping at 100WrmsSub channel @ 4 Ohm load, 75Wrms:Sub channel @ 4 Ohm load into clipping, 121Wrms:Noise, tested with max volume:BT30D non-Pro, audible hiss from speakers during powerup, circuit shuts off when no input signal for 5 secs to prevent constant hissing.BT30D Pro, barely audible hiss from speakers, you have to stick your ear on the tweeter to hear it. no circuit to shut off the signal, it's not needed because it is not audible sitting away from speakers.The TPA3255 chips are hungry AND efficient. If you can feed them, they will put out a respectable amount of power for its size. You can upgrade to a 36V power adapter if you are looking to squeeze more juice out of it. It seems most of the manufacturers using this chip have set their bottleneck to the power adapter. If you are looking for a 2.1 amplifier with passive sub output, look no further.The BT30D Pro is way better than the non-Pro version.Pros:Great build qualityExcellent sound quality, to my ear it’s on par with the Aiyima T9 and RZ50Low noise floorRuns cool and efficientCons:Cannot turn BT offSub frequency needs indication and more linear tuningSmaller BT antenna please