I tested this Fosi device for my rear speakers to get 7.1. The first attempt was a Bluetooth (BT) solution (I later abandoned the BT transceiver due to latency and inconsistent coupling/noise/dropouts). I hooked it up like this: AV Receiver Amplifier Out (not Preamp) >> BT Transmitter >> BT Receiver >> Fosi Amplifier >> Speakers. This was the best solution for BT but since BT wasn't good I just hooked it up like this: AV Receiver Preout >> Fosi Amplifier >> Speakers. This worked great on the old Kenwood VR-8050 and new Polk T-15 bookshelf speakers. Next I'm going to use a fiber optic extension cable. So my connection would look like this: AV Receiver Preout >> (maybe Fosi is here) >> fiber optic transmitter >> 100ft fiber >> fiber optic receiver >> (maybe Fosi is here) > > speakers. In short, this block is solid and has a good hit. I like the treble and bass controls, they work very well and can work consistently. It doesn't get too warm and all I can say is that this is a 5 star device, I've been beating it on various settings over the past week and haven't been careful with it at all. All in all a great device. UPDATE (2/2019) On my Onkyo TX-NR787, this device still works. Right now the best setup is: AV receiver output >> fiber optic transmitter >> 100ft fiber >> fiber optic receiver >> fosi >> speakers. UPDATE (3/2019) Bought an Onkyo TX-RX3100 so I can get 7.2.4. I had to purchase a Thor Fiber Audio Extender F-8A (search the Extron schematic online for unbalanced connections) and the Fosi unit works fine. Remember to use the "pre-outs" that lead to the fiber optic module. The Fosi block has some feedback but I can barely hear it. There is some level adjustment at the receiver to reduce feedback.
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