PC based digital playback basics...
Posted: May 29th, 2021, 2:58 pm
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This is NOT the place to discuss whether PC based playback is better or worse than playing from a CD/DVD/SACD transport straight into a DAC. If you want to open that can of worms, start a thread for that.
For starters, let's define some of the buzzwords we'll need to discuss this. There is often some confusion with the usage of these terms, a big part of this is because a single PC often does more than on thing....
1. Storage. If you're going to use a PC for music playback, you're going to need to have music stored somewhere. This can be on a local hard drive, a NAS, in the cloud, or a streaming service such as Tidal or Qobuz.
2. Server software. This is the piece that allows you to tell the system what music on the storage to play, and, if you have more than one destination, where to play it. This is also where the metadata (artist, track, album, artwork etc.) is collected and presented when you browse or something to play.
3. Renderer. This is where any de-compression, resampling, and format conversion (DSD->PCM for example) is done. This is generally the most CPU intensive part of the process.
4. Bridge. This is where the decompressed/resampled/converted audio gets from inside the PC(s) to an outside link that the DAC can take as an input.
5. Control point. You've got to control it all from somewhere. Many of the options can be controlled directly on the machine that's running the server software, but some can't. Also, having a monitor/keyboard/mouse hooked up to a PC in the listening room can be problematic. Most of the solutions can be remote controlled via either an IOS/Andriod app, or through a web interface.
5. DAC. This one is fairly obvious
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There are some commercial offerings where all five of the pieces are in a single box. I'm not going to discuss that option here, I'm going to assume we'll always be using a separate DAC, or a DAC that has built-in Bridge or Renderer/Bridge. So, from simplest to most complex, here are a few ways to put this together....
A. A single PC that does 1-4 (or 5) above. This is an easy solution to start with, and there are quite a few options. The PC can be running MacOS, Windows or Linux, with several options for software, such as Jriver, HQPlayer, Audirvana, daphile, ap-linux, roon. If you don't start with the very cheapest PC you can find, if/when you move to one of the more complicated solutions that follow, you should be able to re-use the PC as you move on. This is the only solution where having the PC on WiFi rather than Ethernet is acceptable, and then only if you're not streaming from the Internet.
A.5 Same as A, except the you've moved any local storage to a NAS. Having local storage on a NAS is recommended for all the following options.
B. Splitting the functions in 1-4 into multiple PCs. There are, of course, a bunch of different ways to make the split. Many consumer NAS products can have a server app installed on the NAS, but I question whether or not most dedicated NAS products have enough processing power to make effective renderers. In my system at this point, I'm running a separate NAS (FreeNAS) and two PCs, one functioning as a server/renderer, and the second one as a bridge. The engineer in me (for those who don't know, I do have a BS in computer engineering) says that's a better split than having a server only PC and a renderer/bridge PC, especially since the server PC can be outside the listening room where a small amount of fan noise is more likely to be acceptable. If your DAC is network connected, it can serve the role of the bridge PC. Network connected DACs generally CAN perform the renderer functions as well, but that's probably better performed on a more powerful PC. If you send your DAC stuff that's already been rendered, and is always in a format the DAC can handle natively, it won't have to do any rendering.
C. This is where we start getting into the esoteric, and are rapidly reaching the point of diminishing returns. Basically we're starting with B above, but building the PCs with hardware (Ethernet cards, USB cards, linear power supplies etc.) that's been specifically designed to optimize audio playback performance. The sky's the limit here, but I'll let some of the others fill in the details here as I haven't gotten this far yet
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Roscoe