Denon and Marantz 2020 AV receivers now free of HDMI 2.1 bug

Mike Wheatley

Sound United has finally come up with a proper fix for a major HDMI 2.1 glitch in high-end 2020 AV receivers sold by its Denon and Marantz brands. The company has promised that anyone who buys a shiny new model will have a bug-free experience from the get go.


The Denon and Marantz receivers were launched in late 2020 amid a fair amount of fanfare, being the first 8K compatible devices of their kind and promising a super realistic sound experience unlike anything heard before.

Alas, it soon became clear the new receivers were crippled by a major glitch that prevented them from passing a 4K signal at 120 frames per second. Anyone who tried to do so would be presented with an immovable black screen on their TV. And the same went for 8K signals at 60Hz.

It quickly became apparent that the problem was due to a bug in the underlying chipset that powered the receivers, meaning there would be no easy fix through a firmware upgrade.

One interesting quirk was that HDMI 2.1 output in both receivers worked just fine with the PlayStation 5 console, as they remained within that machine's maximum bandwidth for HDMI 2.1. But the signal wouldn’t wok with the Xbox Series X or Series S consoles, nor graphics cards from Nvidia and AMD.

Well, the good news is that Sound United has managed to fix the issue by procuring new HDMI 2.1 chipsets that can handle 4K passthrough at 120Hz, and 8K passthrough at 60Hz, as they’re meant to. It means that any receiver built after May 2021 will provide a glitch-free performance, the company said.

To ensure you’re actually buying one of those newer models, look for a serial number that reads xxxxx7000001 or later, John Archer reported in Forbes. That applies to all Denon AVC-A110, AVC-X6700H, AVC-X4700H, AVC-X3700H, AVR-X2700H, AVR-S960H, AVR-A110, AVR-X2700H DAB and Marantz AV7706, SR8015, SR7015, SR6015, SR5015, SR5015 DAB and NR1711 models.

For those who have already spent a considerable amount of money on an older version of one of those receivers, they’ll have to make do with the external HDMI adapter kit that Sound United began offering in April as a workaround. Because there was no way to fix the issue with a software upgrade, the company promised it would send the free adapter, which contains the correct HDMI 2.1 chip, to anyone who purchased one of the older devices. Simply fill out a form on Denon’s or Marantz’s website and they’ll send it over ASAP.

Alternatively, buyers can opt to skip the first generation entirely and go for one of Denon's or Marantz's newer AV receivers that are also said to be free of any bugs. The 2021 flagship models, the Denon AVC-X8500HA and Marantz AV8805A, both went on sale in summer, priced at £3,699 and £3,899 respectively.

Sound United wasn’t the only company to be affected by the bug. Japan’s Yamaha had a similar issue with its RX-V4A, RX-V6A, RX-A2A, TSR-400 and TSR-700 AV receivers. That company responded, notably somewhat slower than Sound United, by promising to launch a hardware upgrade programme that’s set to begin in the autumn.

It isn’t clear how it will work, but most likely customers will have to send their AV receiver back to the manufacturer to receive the upgrade, or at the very least pop by one of its official stores to get the upgrade.

Yamaha hasn't yet mentioned if it has managed to fix the problem for it newer AV receivers either. So beware that if you opt to purchase one of its boxes, the bug may well still be present.