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Denon & Marantz offer adapter kit to address HDMI 2.1 receiver issues

27 Apr 2021 | Rasmus Larsen |

HDMI 2.1 receivers from Denon, Marantz and Yamaha are still not working as intended six months after launch. Sound United is now offering owners an adapter kit – another box – and has seemingly given up trying to find a permanent fix.

The HDMI 2.1 saga

In October 2020, Heise (or c't magazine) published a report after testing the first HDMI 2.1-enabled AV receivers. It concluded that the HDMI 2.1 chip is faulty by design, resulting in a black screen for most 4K120 and 8K60 signals, and that it may not be fixable via firmware. Six months after? The HDMI 2.1 issues persist. While PS5's HDMI 2.1 output appears to work (as it is within the receivers' maximum bandwidth for HDMI 2.1), a black screen appears when HDMI 2.1 signales from other devices including Xbox Series X are routed through the receivers. Users also experiencing problems with HDMI 2.1 graphics cards from Nvidia and AMD.

Denon 8K ready receivers

Denon's X models are some of the receivers affected by the HDMI 2.1 issue

Companies acknowledge the issue

Sound United, the company behind Denon and Marantz, has acknowledged the issue. - "4K/120Hz RGB signal (8-bit, 10-bit, 12-bit) is confirmed to be affected by this issue," Sound United's Denon support page states (Marantz here). "Other 4K/60Hz and 4K/120Hz YCbCr 4:2:0 signals (8-bit) are confirmed to work without issue." The second part of statement is irrelevant to this specific case as 4K/60 and 4K/120 (4:2:0) fall within conventional HDMI 2.0. Sound United is advising owners to bypass the receiver by connecting the game console directly to the TV and use the TV's HDMI eARC port to output sound to the receiver. However, that defeats the whole purpose of an HDMI 2.1 receiver. Many HDMI 2.0 receivers also support HDMI eARC. Yamaha has also acknowledged the issue. Likewise, it is recommending owners to use HDMI eARC. - "An issue has been identified in certain emerging video signals, such as 4K/120Hz, from select sources, resulting in a loss of picture and sound when passed through AV receivers. Yamaha is aware of the issue," said Yamaha (link). "From the time we first announced the newest AV receivers from Yamaha, such as the RX-V4A, RX-V6A, RX-A2A, TSR-400 and TSR-700, we have stated that we will support emerging HDMI 2.1 capabilities (such as 4K/120Hz pass-through) via future updates. We will address the reported HDMI 2.1 issue via these planned future updates in order to provide customers with the best solution available."

Adapter kit offered as "solution"

Sound United has today announced that it will offer an HDMI adapter kit (SPK618) to affected customers. The extra box is designed to address the issue by converting the signal. - "The SPK618 HDMI adapter solution is designed to remedy a compatibility issue between select Denon A/V receivers that support 4K/120Hz and 8K video resolutions and select gaming consoles that support 4K/120Hz and 8K video resolution output. If you experience a black screen and no audio when trying to pass through 4K/120Hz or 8K signals from gaming devices connected to the 8K input of the Denon A/V receiver, this adapter will help you to get a proper gaming experience. You will be able to register on this page starting May 15th to receive the SPK618 HDMI adapter at no cost," announced Sound United. However, the company's "compatibility issue" claim is not accurate. It is a limitation of the HDMI 2.1 chip and with today's patchwork solution Sound United has seemingly giving up trying to find a permanent fix. More details are available on and

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