First... What is a “Transporter”
Basically you have your music on the cloud or on your PC/NAS. If it’s on the cloud , you will use your smartphone to access your account and play. From your smartphone, in order to send the music to your DAC (DACs have USB and/or S/PDIF inputs) you need a transporter that will be visible (to your smartphone / tablet /PC) as an Airplay device (iOS ) or UPNP/DLNA (Android/PC).
We started designing a digital (S/PDIF) transporter for RPI with one goal in mind: Absolut best S/PDIF output.
Now let me explain… behind the grandiose wording there is an exact science. Since this is a digital stream the most important aspect for “absolut best” is jitter. Jitter in digital domain directly translates into analog errors. Second, is noise. Lowering the noise that’s injected in your DAC will produce some (small-to-none) improvements.
Then we went to work.
10 LDOs, 12 LPF, DC/DC convertors, galvanic isolator, WM8805, flip flops, buffers, NDK oscillators.
Optical had to go… by definition it has a jitter of 4ns. That’s 4000ps. We simply removed it. However, optical has galvanic isolation so we took the decision to use a digital isolator instead that separates the outputs from both RPI and WM8805.
DigiOne has 2 outputs: BNC and plain RCA (coaxial). On both, we have achieved jitter of 0.6ps (1 picosecond – time taken by light in a vacuum to travel approximately 0.30 mm).
Noise. 50uV (batteries have about 12uV of noise).
What we achieved, in our opinion and based on public measurements, is the best transporter at any price point (yes, even when compared with 5k USD/EUR transporters).