Blu-ray disks often contain high-resolution audio formats. Dolby TrueHD and DTS-HD are two Blu-ray audio encoding formats that support lossless high-resolution audio. These systems support up to 8 channels of 24-bit, 96kHz audio, or up to 6 channels of 24-bit 192 kHz audio. These lossless systems combine a lossy compressed core signal with a residual signal to create a lossless transmission system. Early Blu-ray players may not fully support these formats. These early players only have access to the lossy compressed stream and are not capable of true high-resolution audio playback. Newer Blu-ray players combine the lossy stream with the residual stream to assemble lossless high-resolution audio that is bit-for-bit true to the original recording. This application note will show how to create a server that will deliver true high-resolution performance.
Blu-ray disks may seem like an ideal solution for the distribution of high-resolution audio, but there are problems. It is not easy to gain access to the high-resolution audio stored on these disks. Blu-ray players are prohibited from having high-resolution digital outputs. Users are forced to listen to the high-resolution tracks through the D/A converters that are built into the disk player. Unfortunately, these built-in D/A converters are not capable of delivering high-resolution performance. Most players cannot deliver anything better than CD quality to the analog outputs. The lossless high-resolution tracks on the Blu-ray disks may have marketing value, but they are of no benefit to most users.
This problem is not new. The DVD, DVD-A, and SACD disk formats all seemed similarly promising for the distribution of high-resolution audio. DVD video disks could deliver 24-bit, 96 kHz stereo. DVD-A disks could deliver high-resolution surround formats. SACD disks could deliver up to 6 channels of 1-bit DSD, a format that is roughly equivalent to 20-bit, 96 kHz PCM. But, like the Blu-ray players, these earlier disk formats were subject to restrictions that prohibited the inclusion of high-resolution digital outputs on the disk players. These formats also failed to deliver high-resolution audio due to the restrictions on digital outputs. In general, these disk formats have all failed to deliver high-resolution audio. The content is on the disk, but it is completely inaccessible to most users.
An examination of the digital outputs on DVD and Blu-ray players will show that the digital outputs are dumbed down to sample rates of 44.1 or 48 kHz at a bit-depth of 16 bits. These digital outputs are also limited to 2 channel PCM or lossy compressed 5.1 formats. No high-resolution audio is available at the digital outputs on any currently-available player!
One solution is to set up a music server using a PC or Mac. We wanted to play high-resolution surround sound in our listening room here at Benchmark, and we wanted to be able to demonstrate high-resolution surround sound at AXPONA 2015. Our solution was to set up a PC-based music (and video) server. We used a Blu-ray equipped PC running Windows 7 and the JRiver MediaCenter software. A multi-channel digital interface was required to send high-resolution digital audio to 3 or 4 external Benchmark DAC2 converters. We selected a Lynx AES16e PCIe card which provides 16 channels in and out at up to 192 kHz. The 16-channel I/O provided by the Lynx card is overkill given that we only need 6 output channels for 5.1 or 8 output channels for 7.1. Nevertheless, this card is one of the lowest cost options available, and it is very reliable.
Our server is a fairly ordinary desktop PC, but I will include the details of our system so that others can select components of equal or higher speed. We started with an HP Pro3500 PC with an Intel Core i5-3470 CPU operating at 3.20 GHz. This quad-core processor has the power to keep up with the demands of simultaneous high-resolution audio and video decoding. In most cases our CPU usage peaked at about 15%. Our machine is equipped with 4 GB of RAM. We removed the stock hard drive and installed two 2TB SATA hard drives in a mirrored RAID 1 configuration. We needed lots of storage space, and we wanted the redundancy of a mirrored configuration. The RAID options are built into the SATA controller on the HP motherboard and can be configured in the boot-up screens. We installed an LG WH16NS40 Blu-ray drive with a SATA interface and a 16x transfer rate. We opted to use the built-in motherboard video controller which is an Intel HD Graphics adapter with 64 MB of dedicated RAM. It supports DVI digital video outputs at 1080p. We inserted the Lynx AES16e card using one of the available PCIe slots. No other cards or hardware options are installed in our server.
We installed a fresh copy of the Windows 7 Professional 64-bit operating system. We installed Microsoft Security Essentials because it seems to provide resonable virus and spyware protection without bogging down the machine. We then navigated to Lynxstudio.com and downloaded the driver for the AES16e card. We then installed the JRiver Media Center software version 20.
We selected the "performance" power option in Windows 7 (Control Panel/Hardware and Sound/Power Options) and edited the plan's "advanced power settings" to disable all power management functions. We also disabled screen savers and system sounds.
We launched JRiver and navigated to Tools/Options/Audio Output. We then selected the the "ASIO AES16 [ASIO]" audio output device. We navigated to Tools/Options/Audio Output/Volume and selected "Internal Volume". We were now ready to play CDs, unencrypted DVDs, and unencrypted Blu-ray disks.
Many of the high-resolution audio disks produced by AIX Records are unencrypted. The Disks from other record companies are often encrypted and additional software may need to be purchased to play these disks. Recommendations are available in the JRiver help files.
It is very important to set the CD ripping encoder to a lossless format before ripping any CDs to your hard disk. We selected Windows Media Lossless under Tools/Audio/Encoding/Encoder. Other lossless formats such as FLAC and ALAC are also great choices. All will provide identical bit-accurate quality.
Enable the Media Network (Tools/Audio/Media Network). The media network allows bit-transparent DLNA transmission of audio over WiFi and ethernet connections. When properly configured, audio can be sent to or from a smartphone, tablet or PC. DLNA also supports the transmission of video and still images between devices. You can use this function to view photos from your smartphone on your computer screen.
Add the JRiver Gizmo application to your smartphone. All JRiver playback functions can also be controlled using the JRiver Gizmo application for Android devices. The Gizmo app provides a remote control with album artwork displays and is very cool. A Gizmo web interface (WebGizmo) provides the same functions without the need to download an app, but this solution is slightly less convenient. The WebGizmo web interface is currently the only option available for Apple iOS devices.
The AES16e card provides AES digital outputs on XLR connectors. Windows and JRiver assign the output channels automatically.
Channel assignments are as follows:
The Benchmark DAC2 DX converters are equipped with AES XLR inputs. The outputs from the AES16e card can be connected directly to this input on the DAC2 DX. Three DAC2 DX converters will be required for 5.1, four will be required for 7.1. All DAC2 converters will need to be set for volume control bypass (JRiver will control the volume). The DAC2 bypass function is programmable per input and can be enabled for the AES input only.
We have the following signal chain in our listening room:
We also have a Neumann KH 810 subwoofer. We use JRiver's room correction function to redirect frequencies below 80 Hz to the KH 810 subwoofer. JRiver provides the crossovers and mixes these low frequencies with the Low-Frequency Effects (LFE) channel on the surround recording.
We will be operating the following signal chain at the AXPONA 2015 show:
JRiver Server > AES16e > 3 DAC2 DX converters > 5 AHB2 mono power amplifiers > 5 Revel Salon 2 loudspeakers
The system will also include two Revel B112 subwoofers for the LFE channel.
We will be playing lossless 96 kHz 24-bit 5.1 recordings from AIX records. Most recordings will also include HD video which will be displayed on a JVC 4K projector. Our objective was to put together a multi-vendor system that uses the very best components available. Don't miss this opportunity to hear an absolutely extraordinary 5.1 system.
At Benchmark, listening is the final exam that determines if a design passes from engineering to production. When all of the measurements show that a product is working flawlessly, we spend time listening for issues that may not have shown up on the test station. If we hear something, we go back and figure out how to measure what we heard. We then add this test to our arsenal of measurements.
Benchmark's listening room is equipped with a variety of signal sources, amplifiers and loudspeakers, including the selection of nearfield monitors shown in the photo. It is also equipped with ABX switch boxes that can be used to switch sources while the music is playing.
Benchmark's lab is equipped with Audio Precision test stations that include the top-of-the-line APx555 and the older AP2722 and AP2522. We don't just use these test stations for R&D - every product must pass a full set of tests on one of our Audio Precision test stations before it ships from our factory in Syracuse, NY.
Paul Seydor of The Absolute Sound interviews John Siau, VP and chief designer at Benchmark Media Systems. The interview accompanies Paul's review of the LA4 in the December, 2020 issue of TAS.
"At Benchmark, listening is the final exam that determines if a design passes from engineering to production. But since listening tests are never perfect, it’s essential we develop measurements for each artifact we identify in a listening test. An APx555 test set has far more resolution than human hearing, but it has no intelligence. We have to tell it exactly what to measure and how to measure it. When we hear something we cannot measure, we are not doing the right measurements. If we just listen, redesign, then repeat, we may arrive at a solution that just masks the artifact with another less-objectionable artifact. But if we focus on eliminating every artifact that we can measure, we can quickly converge on a solution that approaches sonic transparency. If we can measure an artifact, we don't try to determine if it’s low enough to be inaudible, we simply try to eliminate it."
- John Siau