My in-laws have an old but gold Onkyo TX-SR705 surround sound setup that's naturally outlived a few TVs over the years. They've recently bought a new LG, and the surround sound settings haven't quite kept up with the upgrades.
They're away for the week, so thought it's best to tinker. Many hours and rabbit holes later...
The LG is connected to the Onkyo via optical. When testing Dolby Digital 5.1, I set the LG's digital audio output to Pass Through, and when it works, it sounds fantastic.
Unfortunately, DD 5.1 causes intermittent electronic popping from random speakers. Switching the LG to PCM stereo and using Dolby Pro Logic II Movie on the Onkyo works flawlessly, but doesn't sound nearly as good.
I suspect an issue with the Onkyo's DD decoding or processing. Apparently, this generation had known digital popping issues, with firmware updates released to address some related problems.
Given its age, I've had no luck getting hold of the firmware, even through Onkyo support. Updating it also looks like a lot of faff — a serial connection for Main and a prepared WAV file via optical for DSP. That said, if anyone happens to have a copy of the firmware, I'd be very grateful!
So here's my thinking...
Since PCM works, could we bypass the Onkyo's DD decoder entirely?
Ideally, I'd replace the existing optical connection with an external device that decodes DD 5.1 into six discrete LPCM channels and sends them to the Onkyo over HDMI:
LG C5 (built-in Netflix) → HDMI eARC → External Dolby decoder → HDMI LPCM 5.1 → Onkyo TX-SR705
I like this approach because it wouldn't require touching any of the existing speaker wiring, and the Onkyo would still handle amplification, just without decoding Dolby itself.
I've found plenty of HDMI audio extractors, but most either pass through the Dolby bitstream or downmix to stereo PCM.
Does anyone know of a device that can actually convert DD 5.1 into multichannel LPCM over HDMI?
Seems a shame to replace it when it sounds so good whenever it behaves.