I hope this group can help. 

I have a GTX 1060 going through my 4K 60Hz capable AVR, the . My television, which it plugs into, is full UHD 4K -- the .

When I plug the HDMI directly from the 1060 into the TV I get full 3840x2160 @ 60Hz. However, when I plug it into any HDMI (all of which are HDCP 2.2 / high speed HDMI) into the AVR and then the AVR into the TV I only get 30Hz at 4K.

Other devices yield full 60Hz. It is only the GTX 1060 that steps down to 30hz.

Having exhausted the other options, I am wondering if the card steps down to 30Hz when another device sits between it and the TV? I also get intermittent second-long blackouts when putting it through the AVR.

FAQ:
* Yes, I have all new high-sped cables capable of HDMI 2 / HDCP 2.2 
* Yes, I have manually set the resolution in NVIDIA control panel to 3840x2160 60Hz (it autosteps down to 30Hz when I pipe it through the AVR). That gets me a black screen until it reverts.
* Yes, I have tried every single input on the AVR, all to no avail. 
* Yes, the NR-1607 is fully HDCP 2,2 compliant

The TV people say it's the AVR. The AVR people say it's the video card. The video card people say it's the AVR.

Ok, so let us reason this one out. If you haven't done these steps, then try them.
 
You use the same cable to plug the 1060 into the TV as you plug in to the AVR to the TV, and it works fine at 4K 60Hz?
You already know the cable from the 1060 to the AVR is good, because you plugged it directly into the TV and got 4K 60Hz?
 
You then take known good cables that work from the 1060 to the TV at 4K 60 Hz and now use the AVR, and you no longer get 4K 60 Hz?
 
Then the problem is obviously with the AVR. You need to call the manufacturer to see about a warranty replacement or look though the manual to see if there are any settings that need to be changed. 

Yep. But that doesn't explain why other 4k devices work fine. Marantz/Denon say it's sonething on the card preventing it.

tmattoneill
Yep. But that doesn't explain why other 4k devices work fine. Marantz/Denon say it's sonething on the card preventing it.

I would say your Issue is a Driver Issues not a Hardware Issue.
Your Marantz http://us.marantz.com/us/products/pages/ProductDetails.aspx?CatId=avreceivers&ProductId=NR1607 
The NR1607 is ready for Ultra High Definition vision, too: its advanced video
section is fully compatible with the latest HDMI 2.0a and HDCP 2.2
specifications on all 8 HDMI inputs, allowing it to pass all the latest video
formats to an Ultra HD TV or projector. With 4K 60Hz video, 4:4:4 Pure Color
sub-sampling, High Dynamic Range (HDR) and 21:9, 3D, and BT.2020 pass-through,
it's ready for the next generation of Blu-ray disc players, set-top boxes, games
consoles and streamed/download 4K Ultra HD content.
Yet they seem to not provide any info about connecting the NR1607 to a Computer.
Maybe you can also look on their Forum!
 
 I would think you having a Marantz you could also have gone for GTX 1080 or at least and GTX 1070.
Are your Cables VESA Certified?  Certified Components | VESA
 

I had the 1080 but it was too snug in my node 202 case and the fan blades scraped.

tmattoneill
I hope this group can help. 

I have a GTX 1060 going through my 4K 60Hz capable AVR, the . My television, which it plugs into, is full UHD 4K -- the .

When I plug the HDMI directly from the 1060 into the TV I get full 3840x2160 @ 60Hz. However, when I plug it into any HDMI (all of which are HDCP 2.2 / high speed HDMI) into the AVR and then the AVR into the TV I only get 30Hz at 4K.

Other devices yield full 60Hz. It is only the GTX 1060 that steps down to 30hz.

Having exhausted the other options, I am wondering if the card steps down to 30Hz when another device sits between it and the TV? I also get intermittent second-long blackouts when putting it through the AVR.

FAQ:
* Yes, I have all new high-sped cables capable of HDMI 2 / HDCP 2.2 
* Yes, I have manually set the resolution in NVIDIA control panel to 3840x2160 60Hz (it autosteps down to 30Hz when I pipe it through the AVR). That gets me a black screen until it reverts.
* Yes, I have tried every single input on the AVR, all to no avail. 
* Yes, the NR-1607 is fully HDCP 2,2 compliant

The TV people say it's the AVR. The AVR people say it's the video card. The video card people say it's the AVR.

Product sheet for your AVR says:  HDMI to HDMI Scaling up to 4K 30/25/24.  It does not say it will support 60hz at 4K 4:4:4 . The AVR people should know. I'll wager if you set the output color format in the Nvidia control panel to 4:2:2 or 4:2:0 it will work at 60hz
 
http://us.marantz.com/us/...s&ProductId=NR1607
 
Also since apparently the ad page disagrees with the spec page, who knows?  What is the length of HDMI cable you're using? Are they both 18Gbps rated?

http://us.marantz.com/us/products/pages/ProductDetails.aspx?CatId=avreceivers&ProductId=NR1607
 

tmattoneill
I had the 1080 but it was too snug in my node 202 case and the fan blades scraped.

Did you test it at least?