streamer to amplifier: which cable, which socket, which DAC

Three sockets on a streamer all play the same album. What they're really asking is which box should turn the music into something your amplifier can use.

Turn a streamer and an amplifier round to face you and the back panels can look like a small examination. There is a pair of RCA sockets, a square optical socket, and a single coaxial one that looks like an RCA but is not, and any of the three will carry the same album between them. So most people use whichever lead came in the box, and never find out what they chose.

Here is what all three are really asking. The music leaves the streamer as data and has to become an analogue signal somewhere before it reaches your speakers, and the socket you use decides where. Choose RCA and the streamer's own converter does the work. Choose optical or coaxial and the data travels onwards to the converter inside the amplifier, or to a separate DAC sitting between them. Neither route wins on principle, whatever anyone tells you. The one to use is the connection your two boxes both actually support, with the conversion and the volume control sitting in the places you meant to put them.

the decision behind all three sockets

A streamer fetches digital data, from a subscription service, an internet radio station or a drive somewhere in the house, while your speakers at the far end need an analogue signal with real power behind it, so between those two facts a converter has to appear. You almost certainly own more than one already: every streamer with an ordinary analogue line output has a DAC inside it, and every amplifier with an optical or coaxial input has one too. People buy a third and add it to the chain without ever having established what the first two sounded like. If you have not yet settled whether you need a separate streamer at all, what is a music streamer? asks whether something already in the room does the job.

So the comparison worth making is not digital against analogue in the abstract. It is your streamer's complete analogue output against your amplifier's complete digital input, levels matched and any processing left consistent. Our full DAC guide sets out how to find the converters you already own. Get the clearest, most reliable route working first and leave the comparisons until afterwards, because a cable should never push you into an awkward control setting on the strength of somebody declaring its socket superior.

RCA, and the streamer's own converter

Take the left and right line outputs on the streamer to any ordinary analogue input on the amplifier, marked AUX, CD, LINE or simply numbered. The streamer converts the music before it leaves the box, and the amplifier receives the same sort of line-level signal it would take from a CD player. Where both boxes offer balanced sockets instead, our guide to XLR or RCA sets out when the three-pin connection solves a real problem and when it's only a bigger plug.

One input is not ordinary, and it is the one people reach for precisely because the plugs fit. Never use PHONO. A phono stage exists for the minuscule signal off a turntable cartridge, so it adds far more gain than a line-level source needs, and a streamer plugged in there arrives loud, bloated and heavily distorted. The sockets fit; the signal does not.

The WiiM Pro Plus shows the other trap, because it offers line, optical and coaxial outputs together. Choosing the RCA cable is not the same as choosing the RCA output. The control app has to be set to the matching output as well, and its line-output level has to suit the amplifier receiving it. A system can be wired perfectly and sit in silence because the streamer is quietly sending the music out of a different socket.

optical, coaxial, and handing the job over

Both of these send the data onwards and leave the conversion to whatever receives it. Optical does it with light, so there is no direct electrical path between the boxes at all, and that isolation is genuinely useful rather than a talking point when a ground loop is putting hum into the system. Coaxial carries the same data electrically, down a single 75-ohm cable wearing RCA-shaped plugs. A spare analogue interconnect will often work over a short distance, and plenty of people run one for years without knowing, but a lead made to the digital specification is the proper answer.

The Arcam A5+ takes both coaxial and optical, so either one puts its internal converter in charge. The amplifier has to be switched to the socket you actually used, and the streamer has to be sending a format the Arcam can accept. The same rule applies elsewhere, though supported resolutions and control settings vary, and our optical, coaxial and USB guide covers what each of the three can and cannot do. If those are the two boxes actually in front of you, our worked example of that system runs the whole thing from unpacking to first play.

If both routes are open to you, compare them honestly. Same recording, any unequal EQ or processing switched off, and the playback level matched as closely as you can manage. A slightly louder output almost always sounds clearer and more exciting, and that's a level difference rather than evidence that one converter is better than the other.

the volume control that catches people out

With a normal integrated amplifier, one working volume control is almost always the sane arrangement. Set the streamer to fixed output where its manufacturer recommends it and take the listening level from the amplifier. Turn the amplifier down before changing that setting, because a streamer switched to fixed may immediately send its full configured level, and the speakers will be first to tell you.

Variable output has a proper place, and it is the system where the streamer has deliberately been made the volume controller, feeding a power amplifier or active speakers that expect exactly that. Start low, and confirm the equipment downstream expects a variable signal before you turn anything up. A selectable output voltage or a volume limit helps where it exists, but it is not a substitute for reading what both manufacturers say.

Passive speakers sit outside all of this. They cannot be driven from a streamer's RCA, optical or coaxial outputs whatever the sockets seem to promise, and still need a power amplifier and a proper run of speaker cable. If you own an all-in-one streaming amplifier, the source, converter and amplification already share one box, so there's no streamer-to-amplifier cable to choose.

when everything is correct and nothing plays

Work the path in order rather than swapping cables at random, confirming which output is active in the streamer, which input is selected on the amplifier, and which volume mode the streamer is in, then reseat both ends. Optical plugs frequently still have their protective cap on and only go in one way round, which accounts for more silent systems than it ought to.

Digital clicking, silence, or repeated dropouts usually mean the receiving converter cannot handle the resolution being sent, so drop the output to a format it supports and look for any automatic sample-rate switching. Music that keeps stopping to buffer is telling you about your network rather than your cable, so try Ethernet, or improve the Wi-Fi, before replacing a lead that was never the problem. A hum that appears only once the electrical connection is made is a classic ground loop, and this is where optical earns its keep, because it breaks that path entirely. Never remove a protective mains earth to chase it. That earth is there to protect people, and no amount of silence is worth defeating it.

the two-minute checklist

Choose RCA when you want the streamer's converter doing the work, optical or coaxial when you want the amplifier's. Keep well away from PHONO. Select the matching output on the streamer and the matching input on the amplifier, then check the receiving end supports the format. With an integrated amplifier, fixed output at the streamer and volume at the amplifier is the cleanest arrangement there is, so save variable output for the systems where the streamer is genuinely in charge of level. And when nothing plays, walk the path in order before you blame the cable.

So, which cable, which socket, which DAC? The one your two boxes both support, handing the conversion to whichever converter you have decided should do it. Once that is settled, build the exact cable plan for your system and the back panel stops looking like a test. If you would rather see it decided than described, an Audiolab 7000N Play into a 7000A is a system carrying the same converter at both ends, which is the clearest case of the choice being yours to make rather than yours to get right. Happy listening.