Building a new server for multichannel processing
by, 10-10-2016 at 07:03 PM (1086 Views)
I wanted to build a server that is capable of running multichannel pipeline matrix processing (including convolution) and upsampling to the 8-channel exaSound e28 DAC at DSD256.
One challenge was finding a nice CPU for the task. When the new Broadwell-E generation of CPUs became available the choice became easier. Either 8-core i7 6900K with 3.2 GHz base frequency, or 10-core i7 6950X with 3.0 GHz base frequency. I ended up selecting the 6950X because then there's a core per channel and two extra cores for other tasks like running the OS, Roon, etc. These also have four memory channels for DDR4 2400 RAM to keep the CPU employed.
Next I wanted to select a GPU. Since the GeForce GTX 1080 (check the full specs) based on the newest Pascal architecture became available recently, it was a natural choice. The newest Titan X and Quadro P-series were not yet available. Since I was earlier happy with ASUS Strix-series GTX 980, I picked up GTX 1080 from the same series. Luckily I didn't choose anything bigger, as you'll see later, this is already a monster. Strix-series has three large fans and a large heatsink, making it fairly quiet because the fans then run at slower speeds making less air noise.
Next interesting task was to select a motherboard for the system. I wanted something that was available, and some of the features in Gigabyte's G1 Gaming series are interesting. For example the DAC-UP USB interfaces that have noise filtering and also possibility to turn off the +5V supply from BIOS settings!
Since the microATX size X99M-Gaming5 model had all the necessary features (including UltraDurable), no wireless components and was well available it ended up being selected.
I wanted the computer look like normal audio gear, so I wanted a HTPC case with brushed aluminum front panel and typical measures. Based on previous good experiences, one from Fractal Design's range was a natural choice the Node 605. Now this choice started to place some interesting constraints. For example based on the specs, the graphics card wasn't even supposed to fit...
Now it was necessary to find a PSU that could power all this and be silent as possible. The Corsair RM850x matched my requirements, was available in the store and based on the specs would also fit in the case.
As last items, I selected storage for the OS (music is on a network server) and RAM. For storage, I knew I wanted something extremely fast. Samsung 950PRO M.2 NVMe fit the bill exactly. As an additional bonus it nicely fits on the motherboard which was good since I knew I'd need to remove all the HDD cages from the case to fit the GTX 1080 card. For RAM I ordered fastest spec matching RAM I could get and that was Kingston HyperX Predator DDR4 2400 with CL12 (not available anymore, but similar part is now available in the Savage-series with smaller heatsinks).
Since this module had long delivery time and large heatsinks I wasn't sure if it's going to fit, I also purchased more regular Crucial Ballistix Sport DDR4 2400 with CL16.
For CPU cooler, the only suitable one, that was both expected to be quiet and also fit the case was Noctua NH-U9B that I already had in storage, now replaced in the product portfolio by slightly updated NH-U9S model. The newer model directly supports LGA2011-3, for the older model I took mounting kit from the NH-D15 cooler kit I'm anyway going to use on another machine with LGA1511 socket.
Getting started with the installation, the PSU just fit the case, one millimeter bigger and it wouldn't have fit there.
Looking at the motherboard...
This one has kind of "hifi" sound card on-board, with shielding on the DAC (box saying "AMP-UP Audio"), Nichicon audio caps, adjustable output gain and swappable op-amp (default is TI/BB OPA2134). I'm not going to use it, but there it is anyway... The board looks pretty neat overall.
Then installing the CPU, cooler, RAM and the SSD. Here those parts installed, with the Crucial Ballistix RAM modules. Taller RAM modules would get pretty close to the cooler, I don't know yet if the HyperX Predator modules are going to fit or not.
And then, everything goes into the case. This wasn't easy, I knew it was going to be tight with the Strix-series GTX 1080. In addition to the HDD cages, I had to remove the front panel USB/FW/audio connector board and even then bend top of the rear panel steel for the duration of installation, otherwise the card didn't fit in. But it doesn't matter, because those connectors would be behind front-panel lid and I don't need those anyway. The middle case stiffening rod will need to be left out.
And at last, the machine running, still with lid open. You can see that only middle GPU fan is running because there's no real load on the GPU yet. Fancy led stripes on the motherboard and graphics card that can be adjusted to do different stuff. Not going to be visible in this case...
Here are load figures from the first test run. Source is 5.1 channel 48/16 DVD-rip, upsampled to 12.3 MHz DSD256 using full poly-sinc-short-mp and ASDM7. CUDA offload is being used.