AES3 vs S/PDIF

Q: AES3 vs S/PDIF: Can I plug an AES3 output into an S/PDIF input?

AES3: Two channels of uncompressed digital audio down one balanced pair, self-clocking, on the XLR connector everything else on the stage already uses. It is the reason a digital feed can travel a mic line, and the reason people plug digital into analogue inputs by mistake. S/PDIF: The consumer form of AES3: the same two-channel data format at a much lower voltage, on 75 Ω coax with an RCA connector or on TOSLINK optical fibre. Same bits, different electrical world.

showstack / compare / aes3-vs-spdif

Can I plug an AES3 output into an S/PDIF input? Below is every field we hold on both, side by side. Each one is sourced on the individual entry, and anything nobody could source is left blank rather than guessed.

Side by side

	AES3	S/PDIF
Category	audio-transport	audio-transport
Flow	Media — large, continuous, on time and in order	Media — large, continuous, on time and in order
Transport	other	other
Spec availability	published-paid	published-paid
Steward	AES (Audio Engineering Society), with the EBU	IEC
First published	1985	—
Status	current	current
Our confidence	reported	reported

Both are media flows. Anything that starves the link — usually a management transfer nobody scheduled — and jitter that outruns the receive buffer. That applies equally to either, so it is not a discriminator here.

What each one carries

Capability defined by the specification, not by any one product. A blank means the specification does not fix it, which is itself the answer on a transport like SRT.

	AES3	S/PDIF
Sample rates	32 kHz, 44.1 kHz, 48 kHz	32 kHz, 44.1 kHz, 48 kHz
Audio bit depth	24-bit	24-bit
Audio channels	up to 2	up to 2
Audio encoding	Linear PCM, biphase mark coded	Linear PCM, or a compressed bitstream carried transparently

AES3, audio: Two channels in one subframe pair. Later revisions add higher rates, and the consumer variant of the same electrical idea is S/PDIF.

S/PDIF, audio: The consumer form of AES3. It also carries compressed multichannel bitstreams unchanged, which is why a receiver can be handed something it cannot decode and simply produce nothing.

What goes wrong with AES3

The cable is 110 Ω, not the 45–75 Ω of a normal mic line. A standard XLR cable often works over a short run and then fails as the run gets longer, which makes it one of the more misleading intermittent faults on a stage.

It is self-clocking, so the receiver locks to the sender. Two devices that are both trying to be clock master produce dropouts rather than an error.

S/PDIF carries the same data format on 75 Ω coax at a much lower voltage. They interconvert, but not by rewiring a connector.

Plugging AES3 into an analogue input sends a wideband square wave into a preamp. It is loud, it is unpleasant, and on some systems it is expensive.

What goes wrong with S/PDIF

Nominal 0.5 V peak-to-peak on 75 Ω, against AES3's several volts on 110 Ω. The data survives a converter; it does not survive a soldered adaptor.

Practical coax runs are short — around 10 m is the usual working figure. TOSLINK is shorter still and intolerant of tight bends.

Consumer channel-status bits carry copy-protection flags that some professional receivers act on and others ignore.

Sources

AES3 — Serial transmission format for two-channel linearly represented digital audio data — Audio Engineering Society primary
Interfacing AES3 and S/PDIF (RaneNote 149) — Rane Corporation
IEC 60958 — Digital audio interface — International Electrotechnical Commission primary

Disagree with any of this?

Every claim above comes from one of the two entries and carries a source. If one is wrong, correcting it is a single file and it fixes this page automatically. Edit AES3 or edit S/PDIF.