Digital Cables

That got me thinking, where did the interface come from and in general what are it's advantages over traditional digital cables., so, I asked ChatGPT:

1. Fundamental design differences

I²S

• Originally an internal chip-to-chip bus
• Sends audio data and clocks on separate lines
• External use typically via HDMI connector (connector ≠ HDMI protocol)
• No formal external standard

AES/EBU

• Professional digital audio interface
• Balanced 110-ohm transmission over XLR
• Clock and data are embedded together
• True, globally standardized format

Coaxial (S/PDIF)

• Consumer digital audio interface
• Unbalanced 75-ohm transmission (RCA or BNC)
• Clock and data embedded
• Loosely standardized at the connector level (RCA is not true 75 Ω)

 

2. Clocking and jitter (the core issue)

I²S

• DAC does not recover clock from data
• Avoids PLL / ASRC stages entirely
• Lowest theoretical jitter
• Extremely sensitive to cable integrity and grounding

AES/EBU

• DAC must recover the clock
• Balanced transmission minimizes noise ingress
• Modern DACs suppress recovered jitter very effectively
• Performance is predictable and stable

Coaxial

• Also requires clock recovery
• More susceptible to ground noise
• Greater jitter sensitivity, especially with RCA connectors
• Highly dependent on cable quality and length

 

3. Noise immunity and grounding

I²S

• Moderate noise immunity
• Multiple clock lines increase exposure to interference
• Grounding between transport and DAC is critical
• Can sound exceptional—or brittle—depending on system hygiene

AES/EBU

• Excellent noise rejection due to balanced signaling
• Least sensitive to ground loops
• Designed for hostile studio environments
• Most electrically robust interface

Coaxial

• Poorest noise rejection
• Shares ground between components
• Ground noise often modulates clock recovery
• BNC improves impedance control but not grounding

 

4. Sonic tendencies (when well implemented)

I²S

• Maximum immediacy
• Strong microdynamic contrast
• Very precise imaging and spatial cues
• Can sound exposed or analytical in less optimized systems

AES/EBU

• Slightly rounder leading edges
• Greater tonal density and cohesion
• Excellent rhythmic stability
• Often perceived as more “musical” or relaxed

Coaxial

• Variable depending on cable and DAC reclocking
• Can sound excellent in short runs
• Typically less spatially stable
• Treble can be slightly grainier

 

5. Cable sensitivity

I²S

• Very high sensitivity
• Short runs preferred (often ≤1–2 m)
• Cable quality and impedance control are critical
• Interoperability issues common

AES/EBU

• Low sensitivity
• Works well over long distances
• Cable differences are subtler
• Consistent results across brands

Coaxial

• Highest sensitivity
• RCA impedance mismatch is common
• Cable length and construction matter greatly
• BNC is strongly preferred where available

 

6. Standardization and compatibility

Aspect	I²S	AES/EBU	Coax
External standard	No	Yes	Partial
Interoperability	Poor	Excellent	Good
Vendor dependence	Very high	Low	Moderate
Plug-and-play	No	Yes	Yes

 

7. Why measurements and preferences diverge

I²S often measures best because it removes clock recovery entirely.

However, AES/EBU frequently sounds more coherent in real systems because it:

• Rejects noise better
• Is less sensitive to power and grounding
• Masks implementation flaws less brutally

In practice:

• I²S maximizes resolution and truth
• AES/EBU maximizes stability and flow
• Coax maximizes compatibility and variability

 

8. Practical recommendations

Choose I²S when:

• Transport and DAC are designed to work together
• Cable run is short
• Power and grounding are excellent
• You prioritize spatial precision and microdetail

Choose AES/EBU when:

• Mixing brands
• Cable runs are longer
• You want consistent, repeatable results
• You value tonal density and musical cohesion

Choose Coaxial when:

• AES is unavailable
• DAC reclocking is excellent
• You can use true 75-ohm BNC
• Simplicity and universality matter

 

Bottom line

• I²S: highest ceiling, lowest forgiveness
• AES/EBU: most balanced and reliable
• Coaxial: most variable and cable-dependent

END

 

Sounds like a really tricky interface to use in order to get natural / musical sound. But great for detail.

@ghdprentice 

What a pity you did not get ChatGPT to include HDMI, Ethernet and USB, which presumably are non-traditional digital interconnects!

Of the three, only HDMI is purpose designed for digital audio and only HDMI does not require data to be packetised.. HDMI has four sets of twisted pairs, plus seven single wires.  15 years ago, the standard was upgraded to include 100-Mbps Ethernet using spare pins (HDMI has 19).

Maybe you could expand your query to add these?

Below is a signal-level, audiophile-centric comparison of I²S, AES/EBU, HDMI, USB, and coaxial (S/PDIF), focusing on what actually differs electrically and architecturally, and why listeners often report audible differences in high-end systems like yours.

This is not about marketing claims—it is about clocking, encoding, noise transport, and system topology.

 

1. I²S (Inter-IC Sound)

What it is

• Native internal audio bus, originally designed to move audio inside a device
• Carries separate lines for:
  • Bit clock (BCLK)
  • Word clock (LRCLK)
  • Data
  • Optional master clock (MCLK)

Why audiophiles care

• No encoding or packetization
• No clock recovery required
• DAC receives audio in its original timing structure

Strengths

• Lowest theoretical jitter
• No embedded clock extraction
• No protocol overhead
• Often the most direct sounding: clarity, micro-dynamics, spatial precision

Weaknesses

• No standard pinout
• Poor noise immunity over distance
• Depends heavily on implementation quality
• Usually limited to short cable runs

HDMI-style I²S (important distinction)

• Uses HDMI cables only as a physical carrier
• Not HDMI audio
• Just repurposes the differential pairs for I²S signals

In a well-matched DAC/transport combo, I²S is usually the sonic reference.

 

2. AES/EBU (AES3)

What it is

• Professional digital audio standard
• Balanced 110-ohm XLR
• Encodes audio + clock together (biphase mark coding)

Strengths

• Excellent noise rejection
• Long cable runs (100m+ in studios)
• Electrically robust and predictable
• Less ground noise than coax or USB

Weaknesses

• Clock must be recovered
• Encoding adds timing uncertainty
• Not sample-accurate in the way I²S is

Sonic character (commonly reported)

• Solid, stable, neutral
• Slightly less micro-detail than I²S
• Often superior to coax in resolving systems

AES is the most honest “traditional” digital interface when properly implemented.

 

3. HDMI (Standard Consumer HDMI Audio)

What it is

• Packetized, video-centric interface
• Audio embedded within video clock domains
• Uses TMDS packet framing

Strengths

• High bandwidth
• Multichannel support
• Consumer convenience

Weaknesses

• Not audio-centric
• Heavy protocol overhead
• Clock domains optimized for video, not audio
• Requires reclocking and buffering

Sonic implications

• Often sounds flatter or less refined
• Dependent on downstream reclocking quality

HDMI audio is not designed for audiophile playback—even if the cable quality is high.

 

4. USB Audio

What it is

• Packet-based computer interface
• Asynchronous USB Audio Class 2.0 is the modern standard
• DAC controls the clock, not the source

Strengths

• Supports very high sample rates
• Good isolation possible with modern DACs
• Widely compatible

Weaknesses

• Electrical noise from computers
• Packet timing unrelated to audio clock
• Requires buffering, reclocking, and error handling

Sonic character (system-dependent)

• Can be excellent with top DACs
• Often benefits from:
  • USB isolators
  • Linear power supplies
  • Dedicated streamers

USB is only as good as the DAC’s input stage—great implementations exist, mediocre ones abound.

 

5. Coaxial (S/PDIF over RCA or BNC)

What it is

• Consumer version of AES
• 75-ohm single-ended transmission
• Audio and clock embedded together

Strengths

• Simple
• Ubiquitous
• Can sound excellent over short runs

Weaknesses

• Ground noise
• Impedance mismatches (especially RCA)
• Clock recovery required
• More susceptible to jitter than AES

Sonic character

• Often warm or slightly softened
• Less spatial precision than AES or I²S
• Quality varies dramatically with cable and termination

 

Comparative Summary (Audiophile Perspective)

Interface	Clock Handling	Encoding	Noise Immunity	Implementation Sensitivity	Typical Sonic Rank
I²S	Native, no recovery	None	Low	Very high	🥇 Best
AES/EBU	Recovered	Yes	Very high	Medium	🥈
USB (Async)	DAC-controlled	Packetized	Medium	Very high	🥉 (variable)
Coax (S/PDIF)	Recovered	Yes	Low–Medium	Medium	4th
HDMI Audio	Video-clocked	Heavy	Medium	High	Last

 

Why I²S Often Sounds “Different”

Philosophically, I²S avoids the central compromise of digital audio interfaces:

Every other interface embeds audio timing inside a structure not designed for pure audio.

I²S does not.

That alone explains why many listeners report:

• Better micro-timing
• More precise imaging
• Greater low-level resolution

Not because of magic—because clock recovery is eliminated.

 

Bottom Line (High-End Systems)

• I²S: Best when transport and DAC are purpose-matched
• AES/EBU: Best universal “serious” interface
• USB: Potentially excellent, but implementation-dependent
• Coax: Legacy-friendly, but technically inferior
• HDMI audio: Convenience, not purity

If you’d like, I can map this directly onto your own gear (DAC, streamer, transport) and identify which interface is most likely to be sonically optimal in your system.

Awesome info!! I'm going from a Node N130 to a Denafrips Iris to a Denafrips Pontus 2. My plan is to use USB from the Node to the Iris and then I²S from Iris to Pontus 2. 

Ok just an update. Ive purchased the Denafrips I²S cable for the connection between the IRIS and the Pontus II. I didn't know that they made their own I²S umbilical until today.