When the zeros and ones of digital audio are as correct as possible and — where relevant — the timing is as good as you can get it still isn’t all over!
Ted Smith has mentioned galvanic isolation a few times: it clearly matters to him. Electrical interference can get into your DAC via any of the electrical connections. Galvanic isolation is about getting rid of electrically conductive connections to avoid that kind of interference. I’m interested in ways of achieving it for my DirectStream Junior; I dare say that the same solutions will be applicable to the DirectStream ‘Senior’.
We can’t provide galvanic isolation for the main power input though we can clean up the power as best we can. I use a dedicated mains spur from the house’s distribution unit (US, breaker box) and clean the power going to my audiophile source and power amp using a PS Audio power plant.
This uses electrical conductors. I’ve never heard of another way of getting the signal in although those that use it can take heart from the fact that I²S sources are almost always going to be of audiophile quality.
I believe there’s a way of using an optical cable by Corning to get the signal in but I’m not clear whether it achieves full galvanic isolation. There’s a thread about this. From what I’ve read reliability is an issue.
SPDIF — electrical (phono plugs on a co-axial interconnect)
This uses electrical conductors.
SPDIF — optical often known as TosLink
There’s no electrical connection, so whoopee! However there are technical limitations. It would be good for somebody to summarise those limitations here.
Again there are electrical conductors. Also there are devices that generate electrical noise — computers and switches — along the route from the server’s drive to the DirectStream. Also Ethernet cables may be long which is great for putting a perhaps acoustically noisy server in another room but increases the chance of the cable acting as an aerial for interference.
The wireless cousin of Ethernet is often eschewed by audiophiles because of concerns about data throughput, especially when the domestic WiFi is likely shared by family members watching streamed video. However I’m interested in setting up a WiFi channel dedicated to getting music files from server to DirectStream. The DirectStream has no WiFi connectivity (unlike, for example, the old but much-loved Logitech Transporter [originally Slim Devices Transporter] which had a couple of aerials on the back). However I’m sure there’s a WiFi expert out there who could advise us how to use WiFi access points or range extenders or some such to overcome that.
Finally we all use electrical connections to get the analogue out of our DirectStreams. I suppose there’s an opportunity for electrical interference to get in by that route, along the neutral connection.
I hope I’ve summarised the issue correctly. If electronic engineers need to correct me I welcome it. I now hope to see some discussion about ways of achieving galvanic isolation.