Surround Receivers

Denon/Marantz HDMI 2.1 Solution – SPK618 Adapter – And It’s Free!

We’ve been saying for a while that this is a terrible time to buy a receiver. One of the reasons is that there are very few receivers on the market that have HDMI 2.1 inputs, and only one that has more than one HDMI 2.1 input. On top of that, the receivers that are out there have shown issues passing the very highest quality images and framerates from the Xbox Series X and other sources. If you don’t have this console, or don’t care that you can’t get 4k/120Hz out of it, well, then you probably didn’t notice. But for those that do, this has been an issue.

The Solution

The solution for the HDMI 2.1 problems has been released by Sound United (parent company of both Denon and Marantz) in the SPK618 Adapter. This is a single input, single output, box that sits between your receiver and the Xbox Series X (or any other device with the issue). This takes the signal from the Xbox Series X and “corrects” it. We don’t exactly know what that means, but it should allow you to pass 4k/120Hz or 8k/60Hz through your receiver. The SPK618 Adapter is quite small and is being offered for free from Sound United. If you are not sure if you need one, the affected receivers are:


Denon AVR-A110
Denon AVR-X6700H
Denon AVR-X4700H
Denon AVR-X3700H
Denon AVR-X2700H
Denon AVR-S960H


Marantz AV7706
Marantz SR8015
Marantz SR7015
Marantz SR6015
Marantz SR5015
Marantz NR1711

The Ball that was Dropped

One of the main reasons this year isn’t great for receivers isn’t just because they were having HDMI 2.1 issues. It was because the Denon and Marantz receivers only had one HDMI 2.1 input. Frankly, that just isn’t enough. With two next-gen video game consoles hitting the market recently, you want at least two. Heck, if you want to future-proof your system at all, you’ll get as many as you can.

When Sound United released the SPK618 Adapter solution, they had the chance to leapfrog over the competition. They could have added a couple of more HDMI inputs so that users could have multiple 2.1 HDMI inputs. But they didn’t. You can see the logic. The customer had bought a receiver with only one HDMI 2.1 input, why give them any more? Well, we can think of a lot of reasons. Not the least of which is customer goodwill and loyalty. If I were an owner of one of the above receivers, I’d be pleased by this free solution from Sound United. If they had given me three (or more) inputs, I’d be over the moon.


For current Denon and Marantz receiver owners, the release of the SPK618 Adapter is great news. The SPK618 Adapter is a solution for the HDMI 2.1 problem that many thought would never go away. Not only that, the SPK618 Adapter is free to customers. If you are affected (or just an owner of one of the affected receivers and want the fix “just in case”), head over the Denon and Marantz websites to apply for your free SPK618 Adapter.

11 Comments on Denon/Marantz HDMI 2.1 Solution – SPK618 Adapter – And It’s Free!

    • It is only designed to work with the HDMI boards that are in the Denon. We’ve not heard of anyone successfully using it with anything else. If you try it and it works, let us know!

  1. Matt l Pipke

    I have the adapter, a X3700h a Series x and an Lg Cx 77″ oled.
    the adapter did NOT work for me, Denon says it is an LG EDID issue and cant be fixed unless LG fixes it on their end.
    Is there anyone here with these same components that the adapter worked for?
    SPK618 adapter
    Denon x3700h
    xbx Series X
    Lg Cx.
    Thanks for any information.

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