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Connections
What each input/output on the DAC and streamer tables can actually carry — bandwidth, max PCM/DSD, surround formats, and control. Verified against HDMI.org, IEC 60958/61937, and the USB Audio Class spec.
| Interface | Max bandwidth | Max PCM | DSD | Dolby / DTS | Compression | Control |
|---|---|---|---|---|---|---|
| HDMI ARC | ~1 Mbit/s nominal (underlying S/PDIF channel ~2.3 Mbit/s LPCM) | 2.0 (stereo) LPCM, ≤48 kHz, 16/24-bit | No | Lossy 5.1 only — Dolby Digital ≤640 kbps, DTS ≤1.5 Mbit/s. No lossless/object | 2.0 LPCM uncompressed OR lossy 5.1 | Audio on ARC/HEAC line (pin 14); enabled via HDMI-CEC |
| HDMI eARC (2.1) | ~37 Mbit/s | 192 kHz / 24-bit, up to 8ch (32ch uncompressed) | No (DSD rides the forward HDMI link, not eARC) | Lossy + lossless (TrueHD, DTS-HD MA) + object (Atmos, DTS:X) | Both uncompressed LPCM and compressed bitstreams | eARC data channel (independent of CEC) |
| HDMI 2.2 (eARC) | Same as 2.1 eARC (~37 Mbit/s audio) | Same as 2.1 eARC | No | Same as 2.1 eARC | Same as 2.1 eARC | HDMI 2.2 raises video to 96 Gbps + adds FRL/LIP lip-sync; eARC audio unchanged |
| I²S over HDMI | ~49 Mbit/s @768/32; no fixed ceiling (clock-dependent) | 768 kHz / 32-bit, 2ch (many DDCs/DACs cap at 384k) | DSD512 native typical (DSD1024 on some) | No (raw I²S, no IEC 61937 framing) | Uncompressed raw inter-IC bus | None — proprietary; pinout varies by maker (PS Audio, Denafrips, Gustard…) |
| Coax / BNC S/PDIF | ~9.2 Mbit/s payload @192k | 192 kHz / 24-bit, 2ch | DSD64 via DoP only; DSD128+ impossible | Lossy 5.1 passthrough (IEC 61937): DD ≤640 kbps, DTS ≤1.5 Mbit/s | 2ch LPCM uncompressed OR lossy 5.1 (mutually exclusive) | None (channel-status bits only) |
| Toslink optical | ~9.2 Mbit/s @192/24 (modern); ~6.1 Mbit/s @96k (legacy) | 192 kHz / 24-bit on modern modules (96 kHz on legacy/budget) | DSD64 via DoP only if the module passes ≥176.4 kHz | Lossy 5.1 (same as coax) | 2ch LPCM uncompressed OR lossy 5.1 | None (channel-status bits only) |
| USB Audio (UAC2) | USB 2.0 High-Speed 480 Mbit/s isochronous (UAC1 = 12 Mbit/s) | ≤768 kHz / 32-bit, multichannel (UAC1 ~96 kHz/24-bit) | Yes — DoP or native; DSD512 common, some DSD1024 | Possible (Type III IEC 61937) but rare in hi-fi USB DACs | Type I LPCM (the norm) + optional compressed | USB AudioControl endpoint (format via alt-setting) |
Common myths corrected
- ▸HDMI eARC does NOT carry DSD (a common myth) — DSD/SACD travels on the forward HDMI link. eARC’s real upgrade over ARC is lossless (TrueHD, DTS-HD MA) and object audio (Atmos, DTS:X).
- ▸HDMI ARC carries only 2-channel LPCM, and that stereo PCM is uncompressed (lossy applies only to the DD/DTS 5.1 path).
- ▸Toslink is not limited to 96 kHz — modern optical modules pass 192/24; 96 kHz is only the legacy/budget ceiling.
- ▸HDMI 2.2 does not change eARC audio at all — it raises video bandwidth (96 Gbps) and adds lip-sync signalling.
Sources
- HDMI.org — Enhanced Audio Return Channel (eARC) feature page; HDMI 2.2 spec announcement (CES 2025)
- IEC 60958 / 61937 (S/PDIF physical + compressed-bitstream framing)
- USB.org — USB Audio Class 2.0 (UAC2) specification