Perhaps surprisingly, leading cable designers will tell you: “The best cable
is no cable.”. We went to great lengths, as it were, to make sure that the
Audiophilleos could be connected directly to most DACs without using an S/PDIF
cable. Because the Audiophilleo case is just 3" x 2" x 0.75" (76 mm x 51
mm x 19 mm), its compact size along with an off-center BNC connector, it's
easy install it on almost any DAC with the provided adapters. And the display on
the Audiophilleo1 may even be “flipped” top to bottom so one can read it whether
the device is on the front or rear panel of your DAC.
The Audiophilleo is designed to produce the lowest jitter, and sound best, without the use of a cable. If you already have quality S/PDIF cables, try them out, but the sound may be even better using direct connection. Here’s why:
With an ordinary USB-S/PDIF interface, the sound may improve with a longer, or simply a different, cable, because of improved impedance matching and reflection suppression. Remember that “digital” signals are just oddly-shaped analogue waveforms; like water waves in a pool, they can reflect off the sides and create complicated interference patterns. See Why longer is generally better for an S/PDIF Digital Cable for more.
And, as a general rule, any device driving a short cable must have very fast rise-times or “edges” to avoid jitter created by interfering internal electrical reflections. The relatively slow, 25 ns transitions typical of many USB-S/PDIF devices are more compatible with longer cables, which in turn reduces these reflections and their contribution to clock jitter.
A direct connection is basically a very short cable! The total S/PDIF signal path to the DAC is only 4 inches (100 mm). Thus, the Audiophilleo must have, and has, very fast edge transitions—just 700ps— which eliminates reflection-related jitter even in such a short “cable”.
Electrical signals take about 120 ps to “travel” an inch (25 mm), and in this case, the round-trip for a reflection would be about 960 ps (4 inches x 120 ps, x two “trips”, down and back). Because the edge transition for the Audiophilleo is over in 700ps, the DAC “sees” the first reflection a relatively long time after the time it has evaluated the value of a bit; the reflection can’t contribute to jitter because the DAC has already captured the incoming data correctly.
Audiophilleo1 incorporates an advanced feature, available from the OLED display, that slows down edge transitions for “fine tuning” the sound. Even without using a physical S/PDIF cable, this allows you to experiment with the phenomena caused by different cable lengths. To find out more about cables and jitter, check out the Articles page.