Yes, something is working, thank you very for your help. But for me my journey with low input signal isn't finished yet (but I had some fun today using my method - boosting a signal via filters and gain knobs on iNuke). I'm using optical out (don't have HDMI input in my receiver even). Why do you think I might need decoder (some additional device)? I want to keep my amp in the chain. I want rather come back to adding there my TV (and still use my receiver for TV and Apple Tv), how it was before. Two things still keeps bugging me about low signal when using my receiver. First - this Cleanbox Pro device (what Buttkicker company suggested me to buy) and second one is a pre-amp output on my receiver (RCA). Maybe my receiver send stronger signal than from sub out and then Cleanbox Pro or similar device isn't necessary? Buttkicker company support is very good btw. Here is what they told me: " iNuke is a "Pro" style amp. It's expecting a 1.25 to 1.5V signal strength. You'll need to use a pre-amp (such as this https://www.amazon.com/ART-CLEANBoxPro-2-channel-Unbalanced-Converter/dp/B003S7T49K or similar) to boost the input signal to drive that amp. (...) Unfortunately consumer AV Receivers aren't capable of driving Pro / PA style amps. A PC sound card has a higher signal output voltage than a home theater AVR. An AVR typically is 350mV to 500mV while a soundcard often provides 1V to 2V. The Harman Kardon 3490 lists 200mV. (...) It's very common to use a pre-amp any time a consumer receiver is used to send signal to a Pro Level amp. Typically, anytime you move from RCA to XLR you'll need to boost the signal strength. (...) the pre-amp would be between the HK and the iNuke. The subwoofer output is a mono signal and only needs a signal cable."