I'm using a 35' cable from MyCableMart. It seems to work directly from the Roku Ultra, but again, passing it through the AV8802A causes the issue. However, running directly from the Roku Ultra would require running the cable across the floor which violates the "rule of spouse" which includes language such as: wife must never see cables. Ever. Again." So, that's that.
As far as a cable that supports 18Gbps - it's moot. 4k (UHD) 60Hz at 8-bit is 17.82 Gbps. However, HDR10 is a 10-bit UHD signal, which comes out to 21.38Gbps. So, just about any cable over 20' will fail with the introduction of more resistance. It makes me wonder if Marantz messed up. They brought out the AV8802 before the HDMI standards were set. Then they offered an HDMI board free upgrade for those and came out with the AV8802A that already had the new boards built-in. Are the boards minimum spec for HDMI 2.0 and incapable of HDMI 2.0a specs, which would include higher bandwidth requirements for HDR10? Will they offer another board upgrade program to solve the issue?
On another forum I follow, a poster said they had talked with a rep from Monoprice at CEDIA and that a third generation of active repeater chips were being tested for a target retail date of Feb 2017 that will pass the UHD 10-bit signal properly. I'm not going to worry about it and be patient to see if these cables come out as planned and if there are lengths I can use. If these work and pass the signal, then that solves the 2.0 vs 2.0a question I have. If not, I may have to go to more a more expensive fiber optic HDMI solution and see if that works. If not, then I may have to resign myself to no HDR with the AV8802A.
I bought a first generation PIONEER Dolby Pro-Logic receiver in 1988 during high school. I've seen many things come and go in the AV industry. Waiting a few more months for cable tech to catch-up won't kill me.
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LVR: Samsung UN65JS9500, Marantz AV8802A / MM8077, Roku Ultra, Panasonic BDR (No 4K player till cables work), DTV HR34, XB1, B&W CM10 S2 Towers L/R, B&W CM Centre 2 S2, B&W (4x) CI 700 Series CCM7.4 (SS/SB), B&W DB1 Sub, PCH-VTEN (PLEX Client)
MBR: Samsung UN55JS9000, PIO Elite VSX-90, Roku 4, Pioneer Elite BDR, DTV C31 Client, XB1, B&W (5x) CI Series CCM816, B&W PV1D Sub, PCH-VTEN (PLEX Client)
Headphones and Control: Sony MDR-HW700DS System (Japanese Import) 2x headsets, C4 System
Home PC with PLEX Media Server