Sunday, 28 October 2012

Music Server Gapless Playback, Shielding & LPSU


Continuing A Dedicated Music Server Journey (Part 6)
My next items to address with the server are getting around to shielding the internal cables, and preparing for adding in a linear power supply to replace the existing one. However first, following on from my previous post, Vortexbox have now upgraded the install package to include an option to auto-install Squeezeplay (and disable Vortexplayer) via Yum – which is fantastic. Vortexplayer is reportedly gapless now also, however I believe that is determined more by the hardware implementation of the DAC manufacturer, and so may not be truly gapless 100% of the time. Regarding Vortexplayer being gapless, in the case of the Bel Canto series devices for example, they are very forgiving and have a longish delay when the signal drops before they react and need to relock the sample rate, etc.

As a result a small ½ second or similar gap between tracks often isn’t long enough for them to drop their existing lock – so most of the time (but not always) they don’t introduce a break in the output between tracks... However other DACs, such as my Perreaux DP32, respond virtually instantly to loss of signal (i.e. in less than ¼ of second or whatever) so even the smallest pause in the stream from the server is read as a break and the DAC has to relock onto the signal when it resumes… Regardless however the presence of Squeezeplay as a standard install package, and the fact Vortexplayer is now nominally gapless in most situations is another excellent step forward.

Perreaux DP32 DAC/Preamplifier
(32-bit AES/EBU/SPDIF/Optical & 24-bit USB)
A friend of mine has reported that shielding the cables and adding a Linear Power Supply Unit have been the two biggest items to improve the performance and sound quality of the output, and that they make such a difference for example, that in conjunction with a good quality DAC, it becomes near impossible to pick the difference between a S/PDIF (ASUS Xonar STX PCIe Sound Card) or a USB (SOtM tX-USB 3.0 PCIe Card) signal. This highlights that where people may report an appreciable difference between S/PDIF & USB, that the difference is likely due primarily to the peripheral components and/or the build of the server itself, and not an inherent benefit of any magnitude by one data stream format over the other. And keeping in mind a SOtM USB card is about double the cost of the ASUS Xonar STX it can be well worth giving serious thought to using the lower cost Xonar if you plan to add a Linear Power Supply for example, as any benefits over the Xonar from the SOtM USB may well be negligible.

Cable Shielding
So as mentioned above my next significant step is going to be dealing with shielding the cables internally – I’ve been a bit lax about addressing this for a while, so it’s time to get a move on. In the simplest form it’s about basically wrapping these with foil (as the simplest shield), providing a drain (i.e. an earth wire for the exterior of the foil), and wrapping the whole in an insulator to prevent any unintentional electrical shorting. I plan to do this soon, and will post some photos of the process when I do…

I’ll also be helping another friend assemble a server identical to mine, and will be rebuilding my server with a new Motherboard to facilitate adding an enhanced LPSU (see below) later – so I shall include some photos of the process at the same time I do the cable shielding…

Linear Power Supplies
Once the cabling has been shielded my next step will be to look into adding a Linear Power Supply to the server. This is possibly the biggest improvement one can make, but also the most costly – NZ$500 to NZ$1,000 to build a suitable power supply for an ~NZ$1,200 server – so needs careful consideration and some certainty it will add benefit. Many people may not even notice, or be able to hear, any appreciably difference by adding such a power supply. So it’s critical to determine that first before investing the time & money. Luckily I have a friend who is building one, and as he has a near identical server (in fact the reason I am switching motherboards is primarily to match the one he now has in his server) I will be able to use his LPSU to trial the effect on my set-up, and determine if it’s worth my while investing in one. I’ll post more on this latter when I do my trial.

A Warning About SOtM tX-USB Card Power
One odd thing that a friend has discovered, is the (apparently) poor implementation of the power supply in the SOtM USB Card (the SOtM card has no sensible power routing, and it appears it actually joins all the input buses together and then regulates from there, at about 2 amps, which is not a very good design concept), so if the server (or PC, or whatever) is powered on and the SOtM card does not have its dedicated power supply connected, it will (in simplistic terms) draw too much current through the PCIe slot and basically nuke it – permanently killing that PCIe. If you are ever installing a SOtM USB card always make sure you triple-check you have connected the power supply to it before you turn on the main power to the server or PC! Otherwise if you have a small low power Atom or similar board with only 1 x PCIe slot you could easily end up with a totally unusable board...

Read More: More On Music Server Cables & Shielding
  

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