Low-cost, high-performance Ethernet audio
![[Low-cost, high-performance Ethernet audio]](../jpg/ethernet_audio.jpg)
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Reviewer: Richard Varey - TNT New Zealand
Reviewed: June, 2018
This unit has a super-compact metal case with RPi and DAC+ Pro ($ 40, bundle $ 135), running Volumio. The smallest of those I tried, truly credit card sized, it's the second lightest of those included here. With ultra-low-jitter clocks and gold-plated connectors, it's easy to use and sound quality is excellent. These units are so small that they can easily be tucked away out of sight. There's not much more to say - the website isn't forthcoming.
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I included this vendor because they have an extensive range, including a Sabre ES9038PRO DAC coming soon. I auditioned a sample of their HiFiMe USB DAC ($ 42) which provides a combined 3.5 mm audio jack and optical output (S/PDIF), so it worked well with my desktop music system, but was not suitable as an audiophile component in my main listening system. At just 55 x 35 x 15 mm, it's a surprisingly good DAC.
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The JustBoom range is sold as a stylish way to enjoy HQ music reproduction, and the promise of affordable high definition audio is delivered for sure.
I tried their DAC HAT Kit (£ 115), comprising a RaspberryPi 3 Model B (supplied by RS Components under licence from the RaspberryPi Foundation), a JustBoom DAC HAT, DAC HAT case, JustBoom Player OS SD card (a rebranded copy of Volumio), an Official RaspberryPi Power Supply (supplied with a set of interchangeable international plug pins), and a rather neat RCA cable. The kit also included a 30-day free trial of the Max2Play operating system for RPI, and a 60-day complimentary membership of Roon network music player.
The JustBoom DAC HAT has impressive specifications: Burr-Brown / Texas Instruments PCM5122 DAC chip - 384kHz / 32 bit (due to Linux driver restrictions, max frequency is limited to 192 kHz on the Raspberry Pi); Texas Instruments TPA6133A2 headphone amplifier - 138 mW; fully integrated hardware volume mixing via “alsamixer” or any ALSA compatible application; Integrated EEPROM for automatic Raspberry Pi devicetree driver configuration and fully HAT compatible; Optional Vishay TSOP4838 IR receiver included in package (solder yourself if required); 112 dB signal to noise ratio (SNR) and -93 dB total harmonic distortion (THD +N at -1 dB) for best-in-class audio; Advanced ESD protection on both headphone and RCA outputs; Ultra low noise voltage regulator for the best audio output (LDO 10 μVrms).
At switch-on, it just boots quickly, and the sound quality is truly excellent.
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The 502DAC Pro ($ 129) is, according to the vendor, arguably the most advanced DAC board for the RaspberryPi. with high-resolution analogue output, balanced, single-ended and optical digital transport, and a powerful headphone amplifier. This DAC board converts the RPi's I2S output to high resolution “pro-audio” in both analogue and digital simultaneously. The vendor claims it produces the best digital sound, and analogue sound to match the best alternatives.
Their 502HTA ($ 159) is a high-resolution hybrid tube DAC/amplifier that sits on an RPi streaming audio unit and converts digital audio to analogue for hi-fi headphone listening, with class-leading lowest noise and THD, and “sweet tube” sound. The dual-triode tube amplifies the signal which is then routed to the Class-A solid state buffer to provide the power needed to drive a wide variety of headphones, with selectable attenuation and output impedance.
This unit can also be used as a standalone line amplifier/buffer to properly connect low-drive sources such as smartphones, music players, and LP record players, to an audio system.
High quality components are used from leading manufacturers: Nichicon and Panasonic Audio Capacitors, ALPS Volume Control, Bourns Precision Trimpots, C&K and ALPS Switches and NEC relays. This enables an industry-leading limited 3 year warranty (the tube is guaranteed for 1 year).
Both units deliver superb sound quality, and have operated faultlessly from first boot up.
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This is another serious audiophile unit. The TauDAC-DM101 ($ 399) is an ultra-high performance I2S DAC for the RPi, which delivered some of the best listening in this project! It uses two WM8741 DACs in dual differential mono mode, with ultra-low phase noise oscillators, and ultra-low noise linear regulators. It has separate power supplies for the DACs and the master clock, and it powers the RaspberryPi on which it sits. The design has high quality (tantalum) decoupling capacitors.
The TauOUT-TP101 ($ 249) is a high performance passive output stage for the TauDAC-DM101. The module features Lundahl transformers for summing the differential outputs of the DACs and for galvanic isolation. High-level Lundahl line output transformers provide galvanic isolation between the left and the right channels and between the DAC and the power amplifier, to greatly improve immunity to external noise sources. The massive high-quality RCA connectors are made of non-magnetic, eutectic brass, rhodium over silver plate. The DC power connector is shielded.
Also of note is that the RCA and the DC power connectors are at the same side as the USB and Ethernet connectors of the RaspberryPi, so unlike the other models, the assembly can be cased with all required connectors on the back panel. For some hobbyists, the location of sockets on two faces of the RPi is a frustration of the design. A single 6.3 - 9.1 V DC and at least 1.5 A power supply is needed to power the RaspberryPi and the TauDAC through the TauOUT board. The vendor recommends a high quality power supply, such as a BOTW P&P ECO 9 V from Sbooster, or the iPower 9 V from iFi Audio. The former was supplied with the sample, so I look at it in Part 3.
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This vendor is currently supplying some very interesting evaluation kits for two modules, the ZERO open Linux (PolyOS) board for audio streaming, and the AMP1 amplifier.
Both are very small - the ZERO (€ 39), which is a Pi Zero alternative, is just 65 x 30 x 20 mm - and each has wooden panels instead of the predictable Perspex. The ZERO is a tiny stripped-down cheaper alternative to the RPi and includes analogue output and optical TOSLINK transmitter, and USB-A connector. Connector positions are optimised for audio use. The AMP1 (€ 79) is a 2x35 W fully digital Class-D amplifier, just 65 x 56 x 20 mm! It features optical TOSLINK receiver, analogue line-in, integrated 5 GHz wireless LAN, 1 GHz processor with DDR3 RAM, and embedded DSP.
I imagine that these units will be popular for integration into media player/server projects.
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I also stumbled on the WD PiDrive from WDLabs (part of Western Digital), which combines SD card and USB drive, and one version has a RaspberryPi SBC attached to a WD hard drive. I didn't audition any of these units.
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The Wolfson Audio Card also came to my attention. It extends RPi audio to HD at 24-bit 192 kHz, and is offered as an alternative to a PC soundcard. I didn't get to audition this one, which is a shame as I know Wolfson Audio's reputation.
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The Terra-BerryDAC2+ is available from Terratechnos in Japan, but I didn't audition this unit for this survey. It uses an AKM AK4490 DAC, providing PCM up to 768 kHz 32-bit, and DSD up to 11.2 MHz.
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The NanoSound media player from Hong Kong based Nanomesher.com has a digital transport and DAC, with optional amplifier and speakers. This Kickstarter project is 5 Star rated by the Official RapsberryPi Magazine.
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Whilst researching this survey, I also requested review samples from IQAudio, Pimoroni, and DFRobot, but these companies didn't reply. They also have products that would seem to sit in my high-performance at low-cost consideration set.
Hot off the press! Just as I was completing my write-up, the folks at Etalon alerted me to their server/streamer products.
The StrEamer (€ 550) is a mini server for home network connection, incorporating RJ45 and USB connection, and precision volume control. It's compatible with Logitech Media Server and DLNA, as well as Airplay. It'll play PCM up to 384 kHz 24-bit and DSD 64/128/254. I connected an external harddrive and played superb quality sound to my system.
The musicServer is the high-end big brother, supplied with a custom linear power supply, and their network Isolator built-in. Another outstanding performer.
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In Part 3, I also look at various software options, some of which were supplied pre-installed by vendors. I also consider some enhancement accessories for the RPi and Ethernet connection.
Previous Parts
Part 1
Copyright © 2018 Richard Varey - richard@tnt-audio.com - www.tnt-audio.com
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