HDMI ARC vs Optical: What Each One Can Actually Carry
Use HDMI ARC if the television has the port, because it carries the same Dolby Digital surround an optical cable does and it does it on the cable already running your picture. Reach for optical only when there is no ARC port at all. Neither one carries Dolby Atmos or a lossless track, and eARC is the only one of the three that does.
What decides it: Whether the soundtrack is compressed. Optical and ARC both stop at Dolby Digital, and only eARC goes past it.
HDMI eARC
Pick this if you play discs, or you want the Atmos and lossless tracks at the quality they were encoded in rather than a version that survived the trip.
HDMI ARC
Pick this if the television predates eARC, and Dolby Digital from the built in apps and the tuner is the whole job you need done.
Optical (TOSLINK)
Pick this if the television has no ARC port at all, or you want the audio path to keep working on days the HDMI handshake does not.
None of these is a single product, so there is no pick to link. The table compares the types.
| HDMI eARC | HDMI ARC | Optical (TOSLINK) | |
|---|---|---|---|
| Channels | Up to 32 uncompressed | 5.1, compressed | 5.1 compressed, or 2.0 PCM |
| Atmos / DTS:X | Dolby Atmos and DTS:X | Neither | Neither |
| TV audio return | eARC | ARC | Not a return channel |
Most of the time these two cables do the same job, and nobody leads with that. It is why the question keeps coming back.
HDMI ARC vs optical turns into a real decision at exactly one moment, which is when the soundtrack stops being compressed. Below that line a digital optical cable and an ARC connection hand your receiver the same Dolby Digital 5.1. The difference is how many cables run behind the television and whether its remote changes the volume. Above that line, optical has nothing left and plain ARC has very little.
The receiver is rarely the thing standing in your way. Every current model on the shelf we ranked by what their HDMI inputs actually do carries eARC on its output, so the limit you keep hitting is almost certainly the set on the wall.
HDMI ARC vs optical, settled by what the soundtrack is
Dolby Digital and DTS at 5.1 travel down both, and that overlap covers broadcast, a cable box, and the default surround track on a large share of streaming apps. Onkyo says it plainly in the TX-NR6100 documentation: to get digital surround playback in formats such as Dolby Digital, you connect with an HDMI cable, a digital coaxial cable or a digital optical cable. Any of the three. The manual does not rank them.
So if broadcast and apps are what you watch, the cable already behind the television is the correct one and there is nothing here to fix.
Past that tier they split hard. Denon's manual for the AVR-S770H says the eARC function can transmit multichannel linear PCM, Dolby TrueHD, Dolby Atmos, DTS-HD and DTS:X, and then describes those as "audio formats not compatible with conventional ARC". Read the list twice. Every format worth buying a receiver for sits on the far side of a line that plain ARC does not cross, and optical does not get near.
The one number that separates them is 37 megabits
HDMI's licensing body publishes a bandwidth figure for eARC and none for ARC, which tells you something on its own. eARC runs to a maximum audio bandwidth of 37 Mbits per second, at up to 192kHz and 24 bits, carrying as many as 32 uncompressed channels. That is enough room to hand a disc's lossless track to the receiver untouched, which is the whole reason the feature was specified.
Optical was designed for a world where 5.1 meant a compressed 5.1, and it never moved.
Denon's list of what conventional ARC cannot transmit includes Dolby Atmos by name. That is a manufacturer describing its own receiver, which is the only version of this claim worth repeating. If a particular television is doing something cleverer on the way out, Denon does not document it and we are not going to guess at it for you.
Does an optical cable carry surround sound?
Yes, and that is exactly why the argument survives. Optical has carried Dolby Digital since the format existed, so a 5.1 broadcast arrives at the receiver as 5.1 and sounds like it.
What optical cannot do is uncompressed. Onkyo's specification for a digital input lists PCM support as stereo and mono, to 96kHz, so the moment a source sends plain multichannel PCM the optical path downmixes it or drops it. Denon states the same ceiling from another angle: on the AVR-S770H, only the two channel PCM signal from an optical connector can be sent to a second zone. Two brands, two manuals, one ceiling.
Two channels. On a receiver with seven amplifiers in it.
The idea that optical is the serious surround cable turns up constantly in owner discussion. Across 305 owner comments we counted, thirty one people used the phrase HDMI ARC and ten used digital optical, and the confusion is right there in their wording. One put it flatly: "I heared that only optical cable are capable of transmitting proper dolby surroundsound, what is the situation with the HDMI cable here". Another was asking whether an ARC to optical adapter would deliver Dolby Atmos. It will not, and the paragraph above is the reason.
HDMI ARC vs eARC, and why your receiver is not the problem
Buying a new receiver to solve this is usually the wrong purchase. Denon puts eARC on the output of the AVR-S570BT, its smallest 8K model, and on the AVR-S770H above it. Onkyo puts it on the main output of the TX-NR6100. Three boxes, two brands, one shelf, and every one of them already speaks the format you are trying to get. Everything we have measured on this shelf says the same.
Televisions are the constraint, and they get replaced far less often than the boxes plugged into them, so a set from a few years back has a port labeled ARC, no eARC printed anywhere on the panel, and no firmware update that will ever add one.
One more arrangement avoids the question completely. Run every source into the receiver and send only the picture out to the screen, and the return channel never carries anything you care about. That is the setup the case for skipping the video half entirely assumes, once no HDMI cable is in the chain at all.
Why ARC drops out and eARC does not
Because ARC rides on HDMI Control and eARC does not. The Audio Return Channel was bolted onto a link built to carry video, and it borrows that link's control layer to do anything useful. Denon's wording on the enhanced version is precise: the eARC function uses dedicated control to play back television audio "without passing through HDMI control". HDMI Control is CEC, the feature every brand renames and nobody implements identically, and it is the layer that gives way.
That is why an ARC setup loses volume control after a firmware update, or wakes on the wrong input, or works fine until somebody plugs a streaming stick into a spare port. Nothing broke. A handshake that was always fragile got one more device to negotiate with.
eARC steps around it, and for most people that is the upgrade they actually feel, far more than the bandwidth ever was.
Three things to check on the television before you buy a cable
None of this is settled by the cable you own. It is settled by three settings, and Denon's own troubleshooting page names all three.
- Whether the HDMI port is labeled ARC or eARC. It is printed beside the port, and usually beside one port only.
- Whether eARC is switched on in the television's audio menu. Denon's instruction is to make sure eARC is set to on if that setting exists, and on plenty of sets it arrives switched off.
- What the digital audio output is set to. Denon notes that some devices default to PCM, and a receiver waiting for a bitstream gets a stereo downmix instead of the surround track that was sent.
Get those three right and the cable question answers itself, because the television will only offer you the paths it can actually drive. If you want a fourth, it is the HDMI cable rating: Denon asks for Ultra High Speed on an 8K set and High Speed with Ethernet on a 4K one, and the cheap one in the drawer is neither.