What Goes into a Great Digital Coax Cable
A digital coax cable has one job: carry the signal from your streamer or CD transport to your DAC without adding anything to it. A handful of design choices decide whether it pulls that off, and one of them is the connector almost everyone gets wrong. The D-750 is built to get all of them right.
What the signal is up against
An analog interconnect barely cares about impedance. A digital signal cares a lot. It’s a very fast stream of on-off pulses, and it needs the cable to hold one steady electrical value, its impedance, from one end to the other: 75 ohms. Anywhere that value changes, part of the signal reflects back instead of reaching your DAC, blurring the clean edges the DAC has to read. Those blurred edges are what we call jitter. So the whole job is keeping that one number steady across every part of the cable.
The connector most makers skip
The connector is where the chain usually breaks. The standard RCA plug was invented in the 1940s for analog audio, and it’s wonderful at that job, but it isn’t typically built for digital. Its geometry often lands closer to 30–50 ohms and isn’t tightly controlled. Terminate a good cable with one and you’ve reintroduced, right at the connector, the mismatch the cable spent its whole length avoiding. Most digital coax on the market does this. It’s cheaper and quicker, and it quietly wastes the cable behind it.
The D-750 is finished the other way, with our own RCA-750: one of the very few RCA connectors that maintains a genuine 75-ohm impedance through the body of the connector. It’s a five-piece design where most are two, with a gold-plated pure-copper center pin, proprietary USA construction, and a 7.5 mm entry sized for real digital cable. Cable and connector both holding their impedance, so the transmission line stays continuous end to end. For gear with BNC jacks we also offer true 75-ohm BNC, which is the reference termination for this kind of signal. One honest caveat: your DAC’s jack is still an ordinary socket we can’t change. A true 75-ohm plug removes the discontinuity on the half of the interface that’s ours to control. Not a magic fix, just the part we can do properly.
RCA-750, for reference: genuine 75 Ω through the connector body · 5-piece design · gold-plated pure-copper pin · 7.5 mm cable entry · $18 each.
What goes into the cable
The rest is built into the cable itself. The center conductor is solid, silver-coated pure copper, solid for the most uniform impedance and the fewest places for reflections to start, silver-coated because at these frequencies the signal rides the surface of the conductor. It sits in our Air-PTFE Matrix dielectric at a constant of about 1.4, close to the theoretical best of 1.0 and well below the roughly 2.1 of ordinary PTFE, for the lowest loss and the most uniform behavior across frequency. A two-layer shield, aluminum-Mylar foil plus a heavy braid at 100% coverage, is wound at controlled tension to avoid the periodic impedance bumps that show up as jitter. It’s the same physics premium brands chase at many times the price. We just build it in as standard.
Why it matters now
Digital coax isn’t going anywhere. CD players and transports are still a reference source for a great many listeners, and streamers, servers, and network transports have added a new generation of gear that leans on the same connection. Together they’ve made the transport-to-DAC link one of the most-used connections in a modern system, and coax is still one of the most common ways to make it. The cleaner the edges arriving at the DAC, the less its clock recovery has to fight. The D-750 and its predecessor the D-75 have been a quiet fixture in mastering and recording rooms for the better part of three decades, the same rooms where our D-110 AES/EBU cable earns its living. Studios adopt tools that get out of the way of the work. This one does.
The specifications, published
| D-750 Digital Coax — Specifications | |
| Impedance | 75 Ω, held end to end |
| Center conductor | Solid, silver-coated pure copper |
| Dielectric | Air-PTFE Matrix, dielectric constant ≈ 1.4 |
| Shield | 2-layer: aluminum-Mylar foil + heavy braid, 100% coverage |
| Shield construction | Braid wound at controlled tension (minimizes VSWR spikes / jitter) |
| Bandwidth | Accurate to well beyond 2 GHz |
| Cable diameter | 7.6 mm |
| Termination | RCA-750 (true 75 Ω), true 75 Ω BNC, or “F” |
| Price | From ~$250 terminated · $40/ft bulk |
| RCA-750 Connector — Specifications | |
| Impedance | True 75 Ω, through the connector body |
| Center pin | Gold-plated pure copper |
| Design | 5-piece, proprietary USA construction |
| Cable entry | 7.5 mm (fits large digital jackets) |
| Price | $18 each (sold individually) |
A digital cable is a chain. The D-750 is engineered so every link holds, from the conductor to the connector, because the goal is the same one it’s always been: nothing between the music and you.
In silver, since 1992. Alachua, Florida.