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Audio files transport/server

Silent Angel

Manufacturer: THUNDERDATA Co. Ltd.
Price (in Poland): 7990 PLN

RM503, Building 18, No. 1889, Huandao East
Road, Hengqin District, Zhuhai City,
Guangdong Province, CHINA


Provided for test by: AUDIO ATELIER

Historically, 'STREAMER' meant 'tape drive' - a device for transferring data from computer systems to magnetic tapes for archiving. Currently it is defined as a device used to provide multimedia data from the streaming provider to the user in an UNINTERRUPTED manner. In audio, streamers are simply TRANSPORTS (or players) of AUDIO FILES.

t seems that more and more companies with their roots in "hard" IT business are using their knowledge, combining it with their passion - audio. This is how the best products for playing and streaming audio files are developed. An example is the Japanese company I-O Data, which offers high-end file players under the brand name Fidata, as is also the case with the Chinese company ThunderData Co. Ltd., which has a product line for audiophiles under the Silent Angel brand.

ThunderData Co. Ltd. is a company founded by dr. Eric Jian Huang, former technical director at EMC China. The background of team members covers server, network communication, data management, network storage software, hardware architect engineering, and product marketing. Thunder's CTO Chorus Chuang is also a specialist in network hardware, storage software, digital communication signal, and audio grade NAS.

It is equally important that ThunderData operates in the hi-tech industry and focuses on 5G mobile networks and 8K video signal transmission. As we read on the manufacturer's website, "the Thunder team's goal to improve signals quality of computing, networking, and storage. Currently Thunder has developed 2 series of product lines: Silent Angel and Thunder Data."

"Menu" they currently offer is quite short - in a restaurant it usually suggests good cuisine, and in audio a focus particular subject. Under the Silent Data brand you will find only two complete products: file transport / music server Rhein 1 and the Bonn N8 LAN signal switch. The fact that you can rely on this company competency is evidenced by the fact that it is the ThunderData that manufactures LAN switches for ENGLISH ELECTRIC, a brand currently owned by CHORD COMPANY. You can buy switch with the logo of this British manufacturer called EE 8Switch. This is exactly the same switch as the Bonn N8.


The times when computer specialists thought that reading and distributing audio files, as well as audio signals, are no different from reading and distributing other files, for example ones sent to a printer, are behind us. These were "dark ages" which badly testify to the computer industry, which turned out to be short-sighted and - to be honest - narrow-minded.

The Rhein Z1 from Silent Data can testify to how far we have already come, starting from desktop PCs used to play music, and getting to specialized players and audio files transports (and servers in one).


There are several features of the Rhein Z1 design that attract particular attention. These are:
  • specially developed operating system: VitOS,
  • a 250 GB Silent Angel SSD used as a system disk and 1 TB Silent Angel SSD (optional) data storage disk,
  • up to 2 simultaneous zones for multi-room streaming applications,
  • high quality, rigid aluminum alloy housing,
  • ultra low power consumption SSD and isolated power circuit design inside the SSD to ensure low electrical noise emission from SSD,
  • low power consumption CPU to reduce the electrical noise emission from CPU (<6 W),
  • high quality SATA cable for more stable SSD data transmission.

Each of the above points has been ridiculed many times in the past, just like high-end USB and LAN cables, and then LAN switches. Today it is a natural choices for people working with hi-tech and dealing with the most advanced techniques of data storage and transmission. Maybe it will teach something those for whom the things that are not described in text books don’t exist.

The Rhein Z1 is primarily an audio files transport, with VitOS installed, developed by the parent company. To prevent data loss, such as when downloading a new version of the firmware, the system works in parallel on two operating systems. However, if we want, we can use the ROON software (you have to install it and pay for it yourself). On the Rhein Z1 you can download its version designed for signal sources ("core"), and control application on the smartphone or tablet.

Roon allows you to combine files from different sources in one playlist, for example from hard drives and from Tidal. It's one of the best organized programs that plays music and it is really fun to use. However, you shouldn’t count on it turning a low quality device into a high-end one. The transport or file player should work well with its own system. The test was carried out using Roon.

ThunderData | engineer

The founder of Silent Angel is Chorus Chuang. Now he is the CTO & major product designer, architecture of Thunder Data. Chorus' background was from communication company, Zyxel. Then joined Qnap left Zyxel. Also, he’s been an Audiophile for over 20 years. The beginnings of the Z1 can be traced back to the days in Qnap, a NAS(Network Attached Storage) company. We introduced a NAS product that aims at the Hi-Res music user as the DSD format needs bigger data storage capacity.

At that time, the direction of the NAS product was to reduce the mechanical interference and to build the link to download music from cloud. For us, it was like the 2nd phase of MP3 player. The digital music file is not on the device carrying out the playback - the player streams the Hi-Res file from local NAS. Technology wise, we completed that, the storage capacity headache and playback by local streaming problem was solved. However, the Hi-Res file didn't not meet the excitement we expected, as Mr. Chorus could tell the difference as a audiophile. For IT processional this problem was already solved, but for an audiophile, it is only in the beginning.

Mr. Chorus showed me some "audio NAS" at that time, and pointed out which essential parts of the device needed to be modified and he started to work on his own project to build a device that could really unleash the power of HiRes music. In 2014, he founded the Silent Angel, and developed the first prototype of NAS based player. That is when the story of the Silent Angel started. Later on, some M&A took place for some strategic reasons and the Silent Angel became a brand owned by the ThunderData, and more cloud experts joined us after that.

Though we spent a lot effort re-designing and improving the components for the first few years our player was not as successful as we wanted it to be. It was considered as just another player for HiRes music available on the market. In 2018, we re-examine our approach again and reconsidered the essentials of "music streaming". We found out that we focused too much on the product itself. We used to try to build a new function into the box, to build a server with a more powerful CPU.

At that time, we sat down, trying to figure out the fundamental differences for HiFi users who shift to music streaming. For HiFi users, everyone knows that every change of only one cable impacts the sound. So instead of focusing on the device only, we draw a topology map of what’s happening even before the user hears the music - what is the signal’s path it will go through, what will impact user experience and so on. And then we looked at ourselves to see what we could do to make things better. Based Mr. Chorus’s background, we examined the network part of that equation and decided to work on the network switch. The Bonn N8 is a result of that process. We also redesigned Z1 based on our assumptions.

The idea of the Z1 came for Mr. Chorus, and we have our engineers developing Apps and our Operating System. The Cloud expert is Eric, previous EMC China CTO, audiophile as well. In out opinion the problem with hi-res files is not in their playback. The issue is the need of re-defining the publication and distribution of hi-res music by the music industry. What user likes to buy is not a HiRes music file, they like to pay for the "experience" brought by HiRes music. Under that assumption user needs a professional equipment, it is like a gateway with proprietary built hardware and operating system that is made to enhance the user experience.

Audio files | The transport can download files from a NAS, USB drives, USB sticks, or from an internal SSD disk (optional). The signal out is sent via a USB connection, which already serves "unpacked" files, i.e. an audio signal. To convert them to an analog signal, an external D/A converter with USB input is needed. There is one USB 3.0 port and two USB 2.0 ports. For diagnostic purposes, there is also an HDMI output used to connect a screen.

Transport plays files with PCM and DSD signal. For DSD files, the device supports them up to DSD256, but only in the "native" mode. If the DAC supports only DoP mode, the transport will send DSD64 signal to it. The Rhein Z1 is not equipped with an MQA decoder, in which it resembles transports offered by Fidata and I-O Data brands. Unfortunately, I did not find any more detailed information about the PCM files support - neither on the manufacturer's website, nor in the user manual. This usually means one thing - the device is capable of playing all commercially available audio file types.

Details | The device looks great. This is due to both the CNC machined chassis as well as used materials - the housing was milled from an aluminum block of "aerospace grade quality" and anodized. Black and silver colors are available. This type of housing allows you not to use any cooling fans for the processor, but also greatly reduces vibration. And vibration for devices operating at high frequencies is just as harmful to sound as tube microphonics.

The company also pays a lot of attention to details that are usually overlooked. For example, LAN cables - in the tested device these used for signal transmission have precisely selected impedance, and the power cables are made of OFC copper. Protection against high-frequency interference generated by the transport was also important. To minimize them, a special HF frequency absorbing tape is glued to the bottom of the housing. When Oyaide sent me a similar mat fifteen years ago, I wasn't sure what to do with it. It turns out that others knew ...

Power supply | Silent Angel transport is powered using an external switching power supply via a cable terminated with a 5.5 / 2.5 mm plug. This is a classic plug used in power supplies with a hole in the middle (+). The power supply resembles that used in personal computers and provides a voltage of 12 V DC/3 A. It features a detachable AC power cord. So you can replace the AC cable first, and then the entire power supply, for example with the JCAT Optimo 3 Duo.


The Rhein Z1 was tested in a very similar way to that of the I-O Data SOUNDGENIC HDL-RAS2T. The listening sessions were divided into four parts:

1| with the transport combined with in-build D/A converters of Mytek Brooklyn Bridge and Ayon Audio CD-35 HF Edition,

2| I compared the Silent Angel transport to a files player section of the Mytek Brooklyn Bridge, with the Japanese device connected to its USB input; I compared files played from Tidal, and from Silent Angel operating as server,

3| I compared the Silent Angel transport to SACDs and CDs played using Ayon; the Japanese device was connected to its USB input,

4| I compared the Silent Angel transport to TechDAS AIR FORCE III turntable with SAT LM-09 tonearm and X-Quisite ST cartridge.

Recordings used for the test (a selec- tion)

  • Alice In Chains, Greatest Hits, Columbia CS 85922, DSD64/rip (2001)
  • Cannonball Adderley, Somethin’ Else, Blue Note/Esoteric ESSB-90125, SACD/CD (1958/2015) in: 6 Great Jazz, „MasterSound Works”, Blue Note/Esoteric ESSB-90122/7, 6 x SACD/CD
  • Dead Can Dance, Into The Labyrinth, 4AD/Beggars Japan WPCB-10076, „Audiophile Edition”, SACD/CD (1994/2008)
  • Dead Can Dance, Into The Labyrinth, 4AD/Mobile Fidelity MoFi-2-001, “Silver Line Special Limited Edition | No. 1545”, 2 x 140 g LP (1993/2010)
  • Dead Can Dance, Into The Labyrinth, 4AD/Mobile Fidelity, DSD64/rip (1993/2010)
  • Tame Impala, The Slow Rush, Island Records, Interscope Records, Fiction Records, Caroline International/Tidal, MQA Master 24/44,1 (2020)
  • The Jimi Hendrix Experience, Axis: Bold as Love, Track Records/Legacy | Analogue Production AUHQR 0001, 200 g LP (1967/2018)
  • The Jimi Hendrix Experience, Axis: Bold as Love, Track Records/Legacy | Analogue Production, DSD64 (1967/2018)

High quality, acclaimed transports and file players are divided into those that offer high quality sound and those that are great to listen to. Theoretically they should be the same, but in practice they are two different things. In the first case, the point is that the sound is reproduced in the most precise, resolving and selective way. Everything is at a high level and you get the impression that everything has been pushed to the extremes.

The second way is to provide audio material so that the listener has the greatest comfort in musics perception. This requires knowledge of psycho-acoustics, as well as making some important decisions. For example - is it better to let the cymbals shine, but at the expense of highlighting the music material weaknesses, also highlighting the problems encountered when playing music files, or is it better to round them slightly? Or whether to fill in the bass by creating a large sound volume, adding mass to it, or is it better to let the device clearly differentiate recordings, although at the cost of drying the sound in some cases.

In the most expensive and best files transports (and players) these two philosophies are combined and we get some of this and some of that. Some companies - like Linn - focus on one thing, i.e. precision at all cost, while others - like Fidata - on the other, that is, how to bring the sound as close as possible to what we consider "natural", but at the expense of ultimate precision. The Silent Angel Rhein Z1 transport is closer to the second way of thinking. On the other hand, it is not too far from the first. That is why it is such an interesting device.

Its sound is well-balanced. When the recording is dominated by cymbals, like, say, John Coltrane's Blue Train or a contemporary recording in which they form an important part of the track, like, for example, in the Rooster by Alice in Chains, originally released on the Dirt album, they will sound strong and dense. The treble as presented by this device has something in it that resembles playing music using a good SACD player and a good turntable. It’s not as resolving, nor do they have the same weight, not to mention the three-dimensionality, but - for a files transport - they sound really great.

Thanks to them the sound is open, but not too "boosted up" at the top. The device also differentiates very well the weight and energy of the treble, because it showed exactly what the difference was between the open, saturated with long reverb sound in the This Is How (We Want You to Get High) by George Michael, released on the single with the same title, and - for example - Dreamland by the Pet Shop Boys duo from the Hotspot with a dull, blurred treble. Rhein Z1 is really good at it.

So there is a strong and slightly rounded treble. It is resolving, but also has a slightly closed decay. At this price level it is simply great, and what I am saying refers to a comparison with a four times more expensive (from the Silent Angel + Mytek system) SACD player and several times more expensive turntable - I would like it to be clear about it. But comparing it to the file transport section in Mytek you can hear how the Silent Angel outperforms it.

The other end of the band, i.e. the bass, is slightly boosted and emphasized in the tested device. The sound is delivered with momentum and large phantom images on the sound stage. It's a sound based on strong medium bass and boosted in a lower midrange. Each recording that I played was presented with a close foreground. Sinatra, Billie Holiday, Dua Lipa, Carole King vocals - they simply "ruled". They were dense, in a word - natural.

But this is of course the "naturalness" of the recording we are used to. Rhein Z1 does not have the ambition to reach every corner of the recording, to every subtlety placed somewhere deep there by the producer. I didn't have any problem with that, because it did not affect the listening experience. The music is played by this device in an extremely pleasant way, the recordings are well differentiated, and what I am talking about is just another layer of interpretation that the device imposes on the recordings.

So there is treble, but also bass - low, full, slightly warm - what about the midrange? Although one would expect it to dominate the presentation, it doesn’t. This is not a "warm" presentation, in the sense that the vocals are boosted, or that the band’s extremes are withdrawn. As, I hope, I showed you - this is a "wide" sound, a full-range sound, with a very good differentiation. The fact that eventually vocals and instruments operating in this band’s area - for example, the guitar of Barney Kessel from the Billie Holiday’s album titled Body & Soul - seem stronger, is a results of the emphasis in the bass area, I mentioned. But it is not about "pushing" the midrange forward.

Because it's a really well-organized, cool, "swinging" sound. Dynamics is subordinated to tonality, which is why we perceive the presentation as refined, elegant, well-thought-out. Any recordings will benefit from it, because the already mentioned Alice in Chains, and Bill Evans concert from Montreaux, and Tame Impaal from the last album benefit from it. Silent Angel transport is not "focused" on any style, on one type of sound. It has its own way of interpreting played recordings, but does not try to „push” everything into them, but rather reproduced them adding a little of its own polish or finish on top.

It is a resolving sound. Once again you will hear why the files played from local storage sound better than the same files played from any streaming service. Tidal sounded nice, but listening to albums stored on the local disc resulted in a much more resolving, more dynamic and more natural sound.


Silent Angel is a device that price-wise sits somewhere between I-O Data and Fidata transports. Its sound is not as smooth and as three-dimensional as the Fidata’s, but this is not a big difference. In turn, it is much more resolving than the sound offered by I-O Data transports. In fact, it offers its own way to play music, I mean a set of features that is unique and very attractive.

On the one hand, it's an open sound. There is room here for a lot of treble, for cymbals etc. On the other, it does not allow strong sibilants to dominate the performance, and if the upper midrange in vocals is too strong, as in Holiday's voice, it smooths it out. The lower part of the band is powerful and large, which gives the recordings a very good sense of scale and creates an impression of communing with real instruments, not their toy versions. It's just a very nicely organized sound presentation. With the Rhein Z1 one will be able to listen to any album with pleasure - whether it comes from a disc or streaming service. Good job Silent Angel!


Reference system 2018

1) Loudspeakers: HARBETH M40.1 |REVIEW|
2) Line preamplifier: AYON AUDIO Spheris III Linestage |REVIEW|
3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
4) Stands (loudspeakers): ACOUSTIC REVIVE (custom) |ABOUT|
5) Power amplifier: SOULUTION 710
6) Loudspeaker filter: SPEC REAL-SOUND PROCESSOR RSP-AZ9EX (prototype) |REVIEW|
7) Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|


Analog interconnect SACD Player - Line preamplifier: SILTECH Triple Crown (1 m) |ABOUT|
Analog interconnect Line preamplifier - Power amplifier: ACOUSTIC REVIVE RCA-1.0 Absolute-FM (1 m) |REVIEW|
Speaker cable: SILTECH Triple Crown (2.5 m) |ABOUT|

AC Power

Power cable | Mains Power Distribution Block - SACD Player: SILTECH Triple Crown
Power (2 m) |ARTICLE|
Power cable | Mains Power Distribution Block - Line preamplifier - ACOUSTIC REVIVE
Power Reference Triple-C (2 m) |REVIEW|
Power cable | Mains Power Distribution Block - Power amplifier - ACROLINK Mexcel 7N-PC9500 |ARTICLE|
Power cable | Power Receptacle - Mains Power Distribution Block: ACROLINK Mexcel 7N-PC9500 (2 m) |ARTICLE|
Power Receptacle: Acoustic Revive RTP-4eu ULTIMATE |REVIEW|
Anti-vibration platform under Acoustic Revive RTP-4eu ULTIMATE: Asura QUALITY RECOVERY SYSTEM Level 1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RPC-1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RAS-14 Triple-C |REVIEW|
Passive filter EMI/RFI: VERICTUM Block |REVIEW|


Speaker stands: ACOUSTIC REVIVE (custom)
Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|
Anti-vibration platforms: ACOUSTIC REVIVE RAF-48H |ARTICLE|

  • HARMONIX TU-666M "BeauTone" MILLION MAESTRO 20th Anniversary Edition |REVIEW|


Phono preamplifier: Phono cartridges: Tonearm (12"): Reed 3P |REVIEW|

Clamp: PATHE WINGS Titanium PW-Ti 770 | Limited Edition

Record mats:


Headphone amplifier: AYON AUDIO HA-3 |REVIEW|

Headphones: Headphone Cables: Forza AudioWorks NOIR HYBRID HPC