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Transport Compact Disc

+ D/A converter/preamplifier


Manufacturer: Pro-Ject Audio Systems
Price (in Poland): 4450 PLN + 5350 PLN

Division of Audio Tuning Vertriebs GmbH  
Margaretenstrasse 98 | A-1050 Wien  

Country of origin: AUSTRIA/SLOVAKIA

he start of July was pretty much insanely hot in Poland. It wasn’t quite your 40ºC Turkish or Spanish summer, but to the inhabitant of a Central European country used to mild temperatures in summer and rather low ones in winter, it was nearly tropical. At 32ºC outside my window and little less indoors, testing and reviewing audio components turns into something out of Umberto Eco’s The Name of the Rose (Il nome della rosa, 1980). Goodness – if I at least used D-class amps, like the ones offered by Pro-Ject! But no – my powerful Soulution 710 power amp, the tube-based Ayon Audio Polaris III preamplifier with an outboard tube power supply, and more tubes in my Ancient Audio CD player. Things could only get worse if I had large tube monoblocks or solid state amplifiers working in class A.

When opening the nice-looking, classy products from the Box Design series, (the CD Box RS transport and Pre Box RS Digital, DAC and preamplifier in one), I could count on the fact that at least the source and preamplifier would generate less heat than those in my reference system. This idea had a sensible basis, even if I knew previously that the converter’s output operates in class A. But I opened the boxes while being aware of the fact that the DAC has two parallel amplification circuits in the output: a solid state one and a tube one.
And both of these products are so small and stylish! While bigger than the ones from the DS range, not to mention the lower ranges, they remain light and fresh thanks to Heinz Lichtenegger, a visionary and owner of one of the best-recognized audio companies, the Austrian manufacturer of turntables and “mini” electronics: Pro-Ject.
The nearly square in shape (72 x 206 x 200 mm) CD transport and DAC with preamplifier are the newest additions to the flagship RS series. Showcased for the very first time during last year’s High End 2013 in Munich, they had to wait a whole year to be officially launched for sale. Only this year’s audio show in the capital of Bavaria brought the ready-made products – the same ones that the delivery man brought to my house some time later.

I’ll start with the transport and not only because it’s the first link in the chain, but also because its presence was a surprise to me in the first place. It’s a Compact Disc transport, after all, and not a music file player. The company has offered the latter for the past two years, if I’m not mistaken. The second surprise was the unit’s design. Although it’s small, it’s a classic top-loader with a special chamber for the disc. In this type of product there’s no tray – the disc is placed directly on a platter attached to the motor’s axle, made secure with a clamp and closed with a lid. In terms of concept they look quite similar to the CD players from another Austrian manufacturer, Ayon Audio.
The CD Box RS has a slightly confusing name. It’s just a transport, not a fully-fledged player. Additionally, it can play CD-R/RW discs containing hi-res FLAC files, up to 24-bit and 96 kHz.

It’s equipped with several digital outputs, out of which I2S is the most interesting one, made on a JR45 (Ethernet) link, similar to Ayon. Here, however, the designer decided to make a full use of the advantages of the well-known, valued and probably no-longer available BlueTiger 100 mechanism manufactured by the Austrian company StreamUnlimited. Heinz doesn’t have to travel far to get in touch with those people, because both companies have their offices in Vienna. It’s a CD-ROM transport with an interesting system of signal transmission. If along with the I2S you connect the master clock via a digital cable (from the DAC to the transport), you can use a special system called “Sonic2” that employs the Sonic Scrambling technology. This technology aims to minimize jitter. In this mode the output signal has a 88.2 kHz sampling frequency. Sonic Scrambling, as engineers say, is especially useful when you use D/A converters of the sigma-delta type, linearizing their work at lower levels. Nowadays nearly all converters work this way.

The active Sonic2 state is indicated via a corresponding message on a large LCD screen on the transport, as well as a blue micro-LED in the DAC. The latter obviously has an I2S input as well as master clock output. Other than that, it also has eight other digital inputs: AES/EBU, 2 x RCA, 4 x optical, USB, as well as an analogue input, for a phono stage, for example. In addition to digital to analogue conversion, the Pre can also “manage” the signal, including volume control: it’s a classic analog preamplifier. If that wasn’t enough, the front of the device has a large 6.35 mm headphone jack with an output impedance selector. The USB is special. It accepts a PCM signal up to 32-bit and 384 kHz (meaning DXD), as well as DSD signal (DSD64 and DSD128). The remaining inputs accept PCM 24/192 signal.

Another one of the unit’s properties is associated with the USB input – the presence of two different digital-to-analogue converter chips. To be honest, this is the first time I’ve seen anything like it. The basis is a Texas Instruments PCM1792. It handles signals up to 24/192, although after configuring it correctly it’s possible to feed it with a higher sampling frequency signal. The company suggests to use it for all signals up to 24/192. Then there’s another Texas Instruments DAC on board – perhaps not as good, but newer. The PCM5102 is capable of decoding, in full resolution, a 32-bit signal at 384 kHz sampling frequency (DXD). It’s a DAC chip with integrated analog filters and an output buffer, which doesn’t require any extra components in the signal path. You can switch between these two converters using a little toggle-switch on the front panel.

Toggle switches are also used to select a desired digital filter and output circuit. The former is known in many other products, because a vast majority of modern DAC chips implement two filters – with a steeper roll-off characteristic and with a softer one.
I have also come across two separate output stage circuits, but this isn’t common. The user of the Pre Box RS Digital can choose between two output buffers: a solid stage one or tube-based (6922EH). You switch between them with another toggle switch. In my opinion, the toggle switches look fantastic and are one of the best and most unique parts of this series’ visual design. I have not yet seen a transport or a CD player controlled this way before, though.

A few simple words with…

Wojciech Pacuła: What, in hell’s name, inspired you to come up with a CD transport? In the 21st century?! (OK, I am a staunch CD supporter and have my doubts about audio streaming, but still...)
Heinz Lichtenegger: Firstly, the CD is going to be a niche product for audiophiles and Pro-ject has always been a niche player on the global hi-fi market. Secondly, there are many CDs out there and many CD players unfortunately break down. So somebody who has had a real audiophile CD player, which is broken, will not spend 5000 euro on it, because he is already into Hi-Res streaming. So he searches for an audiophile solution which sounds great but does not cost a fortune – hence our CD transport. Finally, since most audiophile today own a high-end DAC, they don’t need a complete CD player with another built-in DAC but they need a perfect transport.

Please describe two main functions of your transport - Sonic2 and 88.2.
Sonic Scrambling technology is a data distribution technology that improves linearity in multi-DAC designs. The idea behind Sonic Scrambling is to provide highest quality D/A conversion using two DACs per channel in differential mode. However the key is that signals sent to both DACs of a given channel (DAC+ and DAC-) are identical. They are exact sign opposites of each other with a (low level) random biasing signal which is added to DAC+ and DAC- respectively in order to de-correlate the signal’s LSBs from its content. By doing so, low level signal linearity is enhanced as these signals reproduced by the DAC will be of random nature, thus spreading possible signal related distortion effects. In fact it is a mathematical algorithm, which uses dual differential DAC in order to dig more from CD format. 88.2 is simply an internal oversampling of the 44.1 kHz signal.

When is the separate master clock active - only with the I2S?
Correct, the Sonic2 I2S requires 8 wires and we have the RJ-45 connector for it; the master clock must be separate and we use a BNC connector for it.

Will your transport be capable of sending signal via I2S to Ayon's DAC?
Good question. The CD Box RS uses unbalanced I2S with a standard TTL level. So if the Ayon or another DAC uses unbalanced I2S with the TTL level and in the same time you have a cable which fits in both products it should play. The CD Box RS transmits SD, BCK, LRCLK. 

Please tell us a little more about the two DACs inside the Pre Box RS – what are they for?
The basic one is the DAC using two PCM1792 in differential mode. Such circuit is necessary for Sonic2, but it also has benefits for other inputs. It can lower the noise floor and extract more detail. Its dynamic range is up to 132dB. The PCM1792 is a monolithic CMOS integrated circuit that includes a stereo digital-to-analogue converter and support circuitry. The data converters use TI’s advanced segment DAC architecture to achieve excellent dynamic performance and improved tolerance to clock jitter. The PCM1792 provides balanced current outputs, allowing the user to optimize analog performance externally. The PCM1792 accepts PCM and DSD audio data formats.
The PCM5102-based DAC is here mainly for processing audio data from USB with sampling frequency higher than 192 kHz (up to 384 kHz) and bit depth up to 32 bits. This DAC doesn’t support DSD playback. Of course, it can be used for all the inputs, except for Sonic2, if its sonic character better suits listener’s taste than the PCM1792-based DAC.

Who exactly designed these products? Each product has its own design engineer, doesn’t it?
Of course – these two have been designed by our engineer, Marian Mlčoch.

Why is there no single remote control for both units?
We will work on a stylish, metal remote as a separate item.

Pro-Ject in “High Fidelity”
• REVIEW: Pro-Ject 1XPRESSION CARBON CLASSIC + Ortofon M SILVER - turntable + phono cartridge, see HERE
• REVIEW: Pro-Ject Box CD SE + DAC Box FL - CD player+ D/A converter, see HERE
• REVIEW: Pro-Ject ART-1 (+ Denon DL-A100) - turntable (+ phono cartridge), see HERE
• REVIEW: Pro-Ject RPM6 SB + PRO-JECT PHONO BOX SE - turntable + phono stage, see HERE
• REVIEW: Pro-Ject 2XPERIENCE - turntable, see HERE
• REVIEW: Pro-Ject RPM5 SUPERPACK - turntable, see HERE
• REVIEW: Pro-Ject HEAD BOX MkII – headphone amplifier, see HERE

Albums auditioned during this review

  • Anita Lipnicka, Vena Amoris, Mystic Production MYSTCD 244, CD (2013).
  • Billie Holiday, “Billie Holiday”, Clef/UMG Recordings UCCV-9470, „David Stone Martin 10 inch Collector’s Selection”, CD (1954/2013).
  • Branford Marsalis, Hot House Flowers, Sony Records (Japan) SRCS-9213, „Master Sound”, CD (1984/1997).
  • Charlie Parker & Dizzy Gillespie,Bird & Diz, Mercury/UMG Recordings UCCV-9466, „David Stone Martin 10 inch Collector’s Selection”, CD (1952/2013).
  • David Roth, Will You Come Home, Stockfisch SFR 357.4079.2, SACD/CD (2014).
  • Eric Clapton, Journeyman, Warner Bros. Records/Audio Fidelity AFZ 180, „Limited Edition No, 0281”, SACD/CD (1989/2014).
  • John Coltrane, Lush Life, Prestige/Universal Music (Japan), „Jazz The Best. Legendary 100, No. 55”, CD (1961/2008).
  • Kenny Burrell, “Soul Call”, Prestige/JVC JVCXR-0210-2, XRCD2 (1964/?).
  • Laurie Allyn, Paradise, Mode Records/V.S.O.P. Records MZCS-1124, „Mode Vocal Collection”, CD (1957/2007).
  • Martyna Jakubowicz, Burzliwy błękit Joanny, Universal Music Polska 376 131 8, CD (2013);
  • Nina Simone, „Silk & Soul”, RCA/BMG UK & Ireland 2876596202, CD (1967/2004).
  • Patrik Nolan, Piano Gathering Light, Naim naimcd011, CD (1994).
  • Shamek Farrah, First Impressions, Strata-East Records/Bomba Records BOM2402, CD (1074/2006).
  • ShowBand, Punkt styku, GAD Records GAD CD 013, CD (2014);
  • Soundgarden, Superunknown, A&M Records 3778183, „Deluxe Edition”, 2 x CD (1994/2014).
  • Tangerine Dream, Phaedra, Virgin Records/EMI Music JapanVJCP-68667, CD (1974/2004).
  • The Cure, Disintegration, Fiction Records 8393532, CD (1989).
Japanese CD editions are available from

Asking Heinz Lichtenegger, why on earth he offers a CD transport in the second decade of the twenty-first century, I did not mean to suggest that he does not know what he’s doing, let alone express my indignation. I was merely interested in the point of view of a man who has done more for affordable vinyl than anyone else, and over the past twenty years made it possible for thousands - hundreds of thousands - of music lovers to enjoy the music. Almost the entire time of the Box series’ existence, except for the initial phase, when they were just turntable "accessories," Pro-Ject lineup included CD players. But when music file players appeared on the horizon, quickly adapted by Pro-Ject to its needs, it might have seem that nobody serious would ever think about a digital physical medium, except maybe myself and a few other madmen. But something's still up. Listening to CDs, one after another, anyone who has a pair of ears and a brain between them should understand what it is.
The Pro-Ject system offers a very friendly side of digitally encoded music. Not warm or muddy, but just friendly. While not very precise, this term is very helpful in the description of the sound in that it doesn’t so much depict the sound itself but rather how it is received; it generalizes rather than specifies. "Friendliness" in this case means something like an "invitation" to listening; not just to a short demo but to longer auditions. It also means not being too discriminating in the selection of musical material. The Pro-Ject has it all: you can use it to listen to music for hours and it does not matter what you are listening to, provided that it is something you like and identify with. Still, I feel a little uncomfortable proposing this term, generalizing and thus "marking" the sound for good. The reason for the latter is that in the audio literature the category of "friendliness" is associated with a "tube" and "analog" sound. Both are obvious simplifications and in fact constitute stereotypes. For a start, it is sufficient for our purposes to say that the Pro-Ject sounds neither "tube" nor "analog" in the stereotypical sense, and yet you can listen to it for hours.


The number of settings in the transport and DAC is almost overwhelming. The transport can be hooked up via one of several available connectors. But let me say this one thing: it is no coincidence that the company turns our attention primarily to I2S. In addition to word clock being sent over a separate cable, the Sonic Scrambling mode offers a much fuller, smoother and saturated sound. If you have friends who believe that "a bit is a bit", do them a favor and let them try out for themselves. The DAC can work with two types of filters, of which almost every time better sounding was filter No. 2. It basically did the same thing as the I2S link. That was enough. Choosing between the two DAC chips proved more difficult and the choice depended on the type of input signal. In the case of CD, I preferred Texas Instruments PCM1792, mostly because of its superior resolution and differentiation. However, with hi-res signal it was no longer so clear.

The choice of output circuit, i.e. solid state or tube-based, will depend on the sonic character of the rest of your system. It is not true that tubes always sound warmer. This is not the story here. On the contrary – it is the solid-state output that is darker and smoother. Hence, it will be a better choice (together with the Texas Instruments PCM5102 DAC chip) if your system has a tendency to sounding slightly dry or bright. This output seems darker, because it is also less sonorous and not as deep as the tube buffer. And it was the way of building up the body (deeper), showing decay (longer) and bottom end energy (higher) that made me carry out the auditions using the tube output. But this was my choice and it should not be considered the only one and "holy."

The sound of the system is open and delicate rather than imposing. A proper selection of individual settings makes it also deep and sonorous. It also has its own character, to which I will come back later. Here and now, the most important is that we get a very clear presentation. And this results in "friendliness" and "openness." Things that are usually mutually exclusive not just coexist here on an equal footing, because that would suggest their incompatibility and artificial joining, but simply "work together."

Spinning any CD you will hear lots of detail, built up on something greater. The unit is very rhythmical. It does not emphasize the attack, so there is no impression of sound’s hardening or contouring. That could adversely affect its melodiousness, given its open sound.
The resolution is pretty good, although the Pro-Ject is not the kind of audio system to display holographic three-dimensional bodies on the soundstage, let alone reveal the hidden secrets of the mixing and mastering engineer. It's more sort of a one-package-sound, even and simply making sense. The density of the sound, which we get with good recordings, results from clarity and low distortion, and not from boosting a certain frequency range.

I have mentioned unit’s own sonic character. It shows in a slight emphasis around 600-800 Hz, which is exactly the center of audio frequency range. Since the upper midrange is very nicely shaped, and not imposing, the midrange seems to be the number one player. This was confirmed by John Coltrane’s saxophone on his album Lush Life, sounding very nice, with meaty foundation and plenty of detail. Also, the vocals of Anita Lipnicka and Martyna Jakubowicz on their commercial albums, i.e. those produced (in terms of their recording and mastering) mainly for radio station exposure. They are not at all bad and may be considered nearly reference for this type of projects. Some things, such as gentle reverb and softness, are somewhat lacking, though. The Pro-Ject with filter No. 2, I2S connection, master clock and DAC No. 1, had no problem with that. My point is that these shortcomings did not affect the way the discs were played. Of course, moving over to the wonderful Laurie Allyn showed what real vocals are, but it was not the unit’s fault.

The Pro-Ject is not just about midrange, though. While midrange is the first to draw attention, it is not dominant. Midbass is also very, very pleasant. The sense of rhythm I spoke about didn’t come out of nowhere. Of course, it’s most evident with recordings that didn’t seem to show it earlier, like The Cure Disintegration, a rather dark and sonically dirty album, on which the Pro-Ject best showed what it’s so good at: capturing tempo changes and bringing out details that are usually “under the dust.” This can be done quite easily by sharpening and thinning out the sound. The Austrian system does not go that way. It is selective and refined at the same time. Hence, we have a very nice edge and delicate, tasteful body. As I said, it’s easiest to see on this type of recordings.

But perhaps what stuck most in my memory was the album I listened to at the beginning of my auditions, and then again at the end: Patrick Noland’s Piano Gathering Light. I have probably already said that, but let me repeat it from time to time, because it's important for me: meeting a person, creator, artist, makes you look at what he does in a quite different way. First of all, it allows to better focus on that. If we know who we are talking about because we met him closer, we are able to devote more time to his “work” or “composition," whatever it is. We can also better understand what he does through conversation or reading.
Recently, such important "meetings" for me were Zdzisław and Tomasz Beksiński, on account of reading a book Beksińscy. Portret podwójny (“Beksińscy. A double portrait”), and interviews with John Marks (of "Stereophile" fame, see HERE) and Ken Christianson (Pro Musica and Naim Label, see HERE). The latter, creator of the True Stereo recording system, had earlier gained my attention and respect, as I had a lot of Naim albums that I liked both musically- and sonically-wise. But it was my conversation with Ken and our exchange of emails that encouraged me to calmly audition more albums produced by him, to compare them with other productions and to look again at discs that earlier seemed boring to me. Noland’s Piano… was one of them. I am, at the moment, after five or six full listening sessions and I just can’t get enough of it. This is a very early release from Naim Label (then simply Naim), with Julian Vereker, owner of the company, handling mastering duties. The sound is extremely natural, which makes it so endearing. Soft and reserved, yet as close as within hand’s reach. I immediately started buying early Naim releases available at, both jazz and classical music – they’re worth it!
The Pro-Ject slightly withdrew the piano, showing a lot of air around it; this is how it builds up the soundstage. It is not the master of background, as it brings closer the events further down the soundstage. But by focusing on the foreground and a slight distance to it at the same time, it gives it breath and perspective.


Describing the Pro-Ject system I focused on the sound of CDs. I think it's normal. After all, the CD transport is its key ingredient. I am, however, aware that the other system component, i.e. the Pre Box RS Digital, is something completely different.
It does really well as a preamp. Hooking up the system to the high-end Ayon Audio Polaris III [Custom Version] preamp we get a deeper bass and better focus, but at the expense of soundstage width and breath, which are so important in creating the sound from this system. I would therefore say that in this case an external preamplifier is not a good idea.
Headphone amplifier is equally interesting. It has a slightly light sound, which makes the kind of headphones like the Ultrasone Edition 5 or HiFiMAN HE-6 lose some of their great body they show with an external headphone amplifier. But these are extreme examples. With classic headphones from Beyerdynamic and AKG the sound will be very pleasant. Maybe not as resolving as from the analog output, but really cool nevertheless. I'm not sure if an external headphone amplifier from a matching price range, can improve things enough to justify the additional cost. This money can be spent much better, for example on a good anti-vibration platform, power supplies, power cords or isolation boards under the components.
It's hard to pass by the USB input. First of all, because it is so modern but also because with the 32/384 signal we can use a completely different DAC chip. I do not have many of these recordings, perhaps three albums from the 2L label. They sounded delicious on the Pro-Ject. But DSD files were even more fun. It confirmed something I’d noticed over a year ago listening to the Marantz NA-11S1. A DSD recording, as long as it’s "native" and not converted from PCM, is so smooth with a good DAC, so clean and unimposing that it reminds vinyl. Here, the USB sounded very well and I preferred to use it with DAC No. 2, which gave a slightly darker, warmer sound. It was not as resolving as with CDs and DAC No. 1, but it didn’t bother me in the slightest.


The Pro-Ject system is extremely functional. The Pre Box RS Digital is like a "deluxe" version of Swiss Army knife for a Marine officer. It sounds very consistent, clean and deep. The transport is equally interesting, although it is a "closed" system. Connected via I2S, it offers a very credible sound, which you can listen to for a long time without fatigue, but also without falling asleep. Better transports provide lower, more focused bass and better sonority across the whole frequency range. The difference is not large, though, and you will have to pay two or three times more.
We get a system that on the one hand is terribly old-fashioned, because the CD is today synonymous with backwardness, but on the other is extremely modern, thanks to the USB input. Give CDs a try and listen to them the way they deserve it, and you will see what you lose ripping every disc that comes your way. In my opinion, there is no comparison and the CD Box RS wins 10:1. The DAC sounds almost as good on well-prepared high-resolution files, offering even more breath and even more delicate phrasing. Focus is not on the same level, though. The Pro-Ject is like a small gift from someone who loves us.

Pro-Ject’s aluminum enclosures look perfect. I am not sure if the Boxes are still made in the Slovak city of Prešov, as they once were (in an old Edgar factory), but I have to admit that the finish quality is world class. So well anodized aluminum in such large quantities is a big problem. And yet it is just perfect here.
The components are available in silver or in black finish, as the ones under review. Both finish versions sport small, silver toggle switches, often found in professional audio equipment, and for some time in the 1970s also in home audio. The enclosures are made of bolted aluminum panels. The faceplate uses the thickest, 10 mm panel.


This is a top-loader type of transport, with the CD disc inserted from the top. The round cutout is slightly too small to operate the disc comfortably. You need some time to master it. The disc is secured with an aluminum clamp and large aluminum lid. The latter might have a slightly different shape for more convenient operation. As I found out just before the publication of this review, all new units come with these components improved – and apparently they look even prettier.
Unusually for a CD transport, the front panel sports a large color LCD display, the same as used in the music file players from this manufacturer. It displays time and track number, the type of encoding (MP3, WMA or FLAC), as well as CD-Text information, if available. It’s a pity that it so rarely is. Surprisingly, the newest albums from Martyna Jakubowicz and Anita Lipnicka are CD-Text capable. As are, of course, most hybrid SACDs. The many times more expensive Boulder CD player handles it in a similar way to CD ripping software: it is connected to the Internet and downloads the necessary data during disc playback.

The digital signal can be fed out in four ways: via RCA (S/PDIF), TOSLINK (S/PDIF), AES/EBU and RJ45 (I2S) connectors. There is also a BNC input, for external master clock. The unit uses a small external switching power supply. 20 V DC voltage is supplied by cable terminated with a solid mini-XLR connector, similar to that used in AKG headphones. All connectors have gold-plated contact pins.

The transport drive and control board are bought from Vienna-based StreamUnlimited. These are the same specialists who had previously worked with similar designs for Philips, to mention the CD-Pro2, for example. The control circuit is based on a large DSP chip from Analog Devices. The drive is mounted in a thoughtful way on an aluminum platform and pressed from the top with another aluminum plate. The mechanism "floats" on rubber absorbers compressed between aluminum discs. The output stage PCB has been designed in-house by Pro-Ject.
The transport is controlled with a small and not particularly handsome remote control unit. Since it can also be used to operate the music file player, only a few buttons are dedicated to the CD transport. Interestingly, remote control can be used to change the LCD display color.

Pre Box RS Digital

D/A converter/preamplifier sports the same little charming toggle switches as the transport. They are used to turn on the unit, change the headphone amplifier output impedance (5-50-20 Ω), and change the DAC input, filter and type of output. In the center we have a small, aluminum volume knob and adjacent to it a 6.35 mm headphone jack. Tiny blue (unfortunately) LEDs indicate the sampling frequency of the input signal, including DSD, as well as the selected input. The latter are described with numbers rather than symbols. You must therefore remember their order. Number 1 is the USB input, and number 2 is I2S. The analog input is number 10. All connectors have gold-plated contact pins. There are nine digital inputs and one unbalanced analog input. There are also two analog outputs - balanced XLR and unbalanced RCA. The power supply is the same as in the transport.

The whole unit’s interior is packed with electronics. A large printed circuit board is mounted to the bottom of the enclosure, with no less than six auxiliary boards and two small boards with tube sockets plugged in to it. The first board houses the USB input circuit. The converter is based on the XMOS SK1220L chip. Adjacent to it is a board with two very nice clock oscillators, separate for both sampling frequency families (44.1 and 48 kHz). There is also a separate clock for the XMOS circuit. Next we have two boards with the proper digital-to-analog converters. The more important one uses two stereo Burr Brown PCM1792 chips, one for each channel. The next board houses a single Burr-Brown PCM5102 chip. The latter does not require external I/U conversion and filters, because they are all build in. This makes the work of designers easier, but does not allow to create a higher quality audio path. Such as the one used by the PCM1792. Here, the conversion circuit and filters use NE5534 opamps and polypropylene capacitors. DAC outputs are switched by small relay switches.

The preamplifier is built using the same opamps. Signal attenuation is handled by a black Japanese Alps motorized potentiometer (Pro-Ject literature says it’s a blue Alps). Adjacent to it, near the headphone jack, is a large headphone amplifier board. It looks very nice. The circuit is based on BCP52+BCP55 bipolar transistor pairs, working in push-pull class A. There are two different preamplifier output stages. One uses two Electro-Harmonix 6922EH tubes, one per channel; the other one sports IRF510S MOSFETs. A two-track potentiometer already suggested it, but now it can be seen clearly that the circuit has an unbalanced topology. Hence, it is better to first try RCA inputs and then the XLRs. The output coupling capacitors are nice-looking Wimas. It needs to be added that a large part of the interior, including one of the auxiliary boards, is occupied by power supply circuits. Remote control unit is tiny, with membrane buttons. It is used to select the input and change volume level.

Specifications (according to the manufacturer)

Supported types of discs: CD, CD-R, CD-RW and Hybrid-SACD
Digital outputs:
• 1x I²S via RJ45 (for use with DAC Box RS or Pre Box RS Digital))
• 1x AES/EBU (XLR)
• 1x co-axial (S/PDIF)
• 1x optical Toslink
External clock interface: BNC (for use with DAC Box RS or Pre Box RS Digital)
Outboard power supply: 20 V/3000 mA DC; 100-240 V, 50/60 Hz
Standby power consumption: < 1 W
Power consumption: 600 mA max/90 mA
Dimension H x W x D: 72 x 206 x 200 (240) mm (D with sockets)
Weight: 3200 g (without power supply)

Pre Box RS Digital
• DAC1 – 2 x PCM1792 24/192
• DAC2 – PCM5102 32/384
Tube complement: 2x Electro-Harmonics 6922EH
Digital inputs:
• 1 x USB 2.0 Audio 32/384 + DoP-DSD 64/128
• 1 x RJ45 Sonic I2S for CD Box RS in Sonic Mode
• 2 x S/PDIF 24/192, 4 x S/PDIF TOSLINK 24/96
• 1x AES/EBU 24/192
Line-level input: 1x RCA
Input impedance: 33 kΩ
Analog outputs: Pre-out (XLR & RCA), Headphone (6.35 mm jack)
Headphone impedance: 5/20/50 Ω switchable
Analog input sensitivity: 1.6 V RMS
Frequency response: 20 Hz – 50 kHz (+ 0/- 0.1 dB)
Signal to noise ratio: -100 dB (IEC-A)
THD: 0,005% - solid state output | 0.25% - tube output
Master clock output: 16.9344 MHz for CD Box RS in Sonic Mode
Outboard power supply: 20 V/3 A DC
Power consumption: 300 mA – solid state | 850 mA – tube | 90 mA - standby
Dimensions W x H x D: 206 x 72 x 200 mm (210 with sockets)
Weight: 1950 g (without power supply)



- Turntable: AVID HIFI Acutus SP [Custom Version]
- Cartridges: Miyajima Laboratory KANSUI, review HERE | Miyajima Laboratory SHILABE, review HERE | Miyajima Laboratory ZERO (mono) | Denon DL-103SA, review HERE
- Phono stage: RCM Audio Sensor Prelude IC, review HERE
- Compact Disc Player: Ancient Audio AIR V-edition, review HERE
- Multiformat Player: Cambridge Audio Azur 752BD
- Line Preamplifier: Polaris III [Custom Version] + AC Regenerator, regular version review (in Polish) HERE
- Power amplifier: Soulution 710
- Integrated Amplifier: Leben CS300XS Custom Version, review HERE
- Stand mount Loudspeakers: Harbeth M40.1 Domestic, review HERE
- Stands for Harbeths: Acoustic Revive Custom Series Loudspeaker Stands
- Real-Sound Processor: SPEC RSP-101/GL
- Integrated Amplifier/Headphone amplifier: Leben CS300XS Custom Version, review HERE
- Headphones: HIFIMAN HE-6, review HERE | HIFIMAN HE-500, review HERE | HIFIMAN HE-300, review HERE | Sennheiser HD800 | AKG K701, review (in Polish) HERE | Ultrasone PROLine 2500, Beyerdynamic DT-990 Pro, version 600 - reviews (in Polish): HERE, HERE, HERE
- Headphone Stands: Klutz Design CanCans (x 3), review (in Polish) HERE
- Headphone Cables: Entreq Konstantin 2010/Sennheiser HD800/HIFIMAN HE-500, review HERE
System I
- Interconnects: Acrolink Mexcel 7N-DA6300, review HERE | preamplifier-power amplifier: Acrolink 8N-A2080III Evo, review HERE
- Loudspeaker Cables: Tara Labs Omega Onyx, review (in Polish) HERE
System II
- Interconnects: Acoustic Revive RCA-1.0PA | XLR-1.0PA II
- Loudspeaker Cables: Acoustic Revive SPC-PA
System I
- Power Cables: Acrolink Mexcel 7N-PC9300, all system, review HERE
- Power Distributor: Acoustic Revive RTP-4eu Ultimate, review HERE
- Power Line: fuse &#8211; power cable Oyaide Tunami Nigo (6m) &#8211; wall sockets 3 x Furutech FT-SWS (R)
System II
- Power Cables: Harmonix X-DC350M2R Improved-Version, review (in Polish) HERE | Oyaide GPX-R (x 4 ), review HERE
- Power Distributor: Oyaide MTS-4e, review HERE
- Portable Player: HIFIMAN HM-801
- USB Cables: Acoustic Revive USB-1.0SP (1 m) | Acoustic Revive USB-5.0PL (5 m), review HERE
- LAN Cables: Acoustic Revive LAN-1.0 PA (kable ) | RLI-1 (filtry), review HERE
- Router: Liksys WAG320N
- NAS: Synology DS410j/8 TB
- Stolik: SolidBase IV Custom, read HERE/all system
- Anti-vibration Platforms: Acoustic Revive RAF-48H, review HERE/digital sources | Pro Audio Bono [Custom Version]/headphone amplifier/integrated amplifier, review HERE | Acoustic Revive RST-38H/loudspeakers under review/stands for loudspeakers under review
- Anti-vibration Feets: Franc Audio Accessories Ceramic Disc/ CD Player/Ayon Polaris II Power Supply /products under review, review HERE | Finite Elemente CeraPuc/ products under review, review HERE | Audio Replas OPT-30HG-SC/PL HR Quartz, review HERE
- Anti-vibration accsories: Audio Replas CNS-7000SZ/power cable, review HERE
- Quartz Isolators: Acoustic Revive RIQ-5010/CP-4
- FM Radio: Tivoli Audio Model One