General Information

The advanced DAC Box RS is a reference-class D/A converter for all kinds of digital stereo sound sources. It superbly acts as a superior USB audio interface for demanding computer audio, also features AES/EBU input and I²S interface for use with CD Box RS. For the engaged audiophile we provide full DSD capability (up to DSD128) over PCM. All inputs fully support 24/192kHz HD music data (optical inputs 96/24) in fully asynchronous mode.

Additionally DAC Box RS incorporates a pair of the best audio grade DAC chips, PCM 1792, which only can be found in expensive high-end designs. 2 different digital filter settings are selectable to meet your favourite sound preferences. Additionally we realized that its also depending on customers taste and type of music/recording, what technology for the outputstage is preferable. More warm and relaxed sounding with Tubes or Solid State Class A with limitless details and dynamics. The DAC Box RS has both options to select!

The whole audio circuitry design is ultra low noise and ultra linear with very low output impedance to avoid any negative interference with cables or pre-amps.

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Latest reviews

Brooko

Brooko's Reviews | Brooko's Blog

4.00 star(s)
Aug 1, 2016

Pros: Build, sample/rate support, SQ, low distortion, transparency, ability to choose SS or tube, form factor, input variety

Cons: Occasional Win 10 driver issues, price, funky power connector

For larger views of the photos (1200 x 800) - please click on the individual images

INTRODUCTION

I'm a guy who likes hearing new gear, but who is also actually pretty happy with my own set-up at the moment. My main desk-top set-up is not high end – but I can easily lose myself in the moment with music, and ultimately that's what I think we all strive for. My main system for some time has been the iFI Micro iDSD, and I sometimes choose to pair it with Little Dot MK IV, and usually with my HD600 or Beyer T1. Nowadays I run a Linux system, and have a paid copy of J River Media Center 21 for Linux.

Then in March this year, Felix from Pro-Ject Audio contacted me out of the blue to ask me if I'd like to have a listen to their Pro-Ject DAC Box RS. They describe it as a reference-class D/A converter, but with some interesting features:

Dual Texas Instruments PCM-1792 DAC chips
Selectable filters
Double DSD capable
Multiple inputs (up to 9)
Both tube and solid state output

So after a bit of discussion I agreed to give it a good run, and in late April it arrived. So through May and June I've been using it as part of my daily system. Hopefully this review will give you some information on who Pro-Ject Audio is, and my personal thoughts on the DAC Box RS.

ABOUT PRO-JECT AUDIO
I have a confession to make – before Felix contacted me, I had no idea who Pro-Ject Audio was, and that included what they made. While I was waiting for the DAC Box RS to arrive, I had plenty of time to do some research into the Company, and also to acquaint myself with what they do. My first search on their website revealed very little – just that they seem to have some pretty nice looking systems, and that they are a division of Audio Tuning Vertriebs GmbH, and are based in Austria. Time to do some more digging!

After a bit more research I found out that Pro-Ject Audio has been around for more than 25 years (started in 1990). The founder (Heinz Lichtenegger) partnered with a turntable factory in a small town called Litovel (Czechoslovakia), and set about refining a line of low-cost, well designed turntables for lovers of vinyl. They still have the same team today, and still use the same factory, and have now branched out into a full product range – which includes digital and analogue audio systems, and covers everything from budget to high-end systems. What seems to be a feature of their product lines though is simple and clean European styling, and well designed components with good measurements and equally good sound. Their philosophy is simple. Their products should be:

simple to use
have true HiFi stereo sound
be great value
have long term stability

The DAC Box RS I'm reviewing today is from their Reference Series. You can view their full product range from their website: http://www.box-designs.com/

DISCLAIMER
The DAC Box RS is a loaner review unit, and as such will be returned to Pro-Ject Audio at the completion of the review. I did not solicit the review unit – Pro-Ject Audio approached me for the review. I am not associated with them in any way, get no financial gain from the review, and this is my honest opinion of the DAC Box RS.

PREAMBLE - 'ABOUT ME'.

I'm a 49 year old music lover. I don't say audiophile – I just love my music. Over the last couple of years, I have slowly changed from cheaper listening set-ups to my current set-up. I vary my listening from portables (including the FiiO X5ii, X3ii, X7, LP5 Pro and L3, and iPhone 5S) to my desk-top's set-up (PC > USB > iFi iDSD). Dpending on my mood I also use my LD MK IV. I also use a portable set-up at work – usually either X3ii/X7/L3 > HP, or PC > E17K > HP. My main full sized headphones at the time of writing are the Beyerdynamic T1, Sennheiser HD600 & HD630VB, and AKG K553. Most of my portable listening is done with IEMs, and lately it has mainly been with the Jays q-Jays, Alclair Curve2 and Adel U6. A full list of the gear I have owned (past and present is listed in my Head-Fi profile).

I have very eclectic music tastes listening to a variety from classical/opera and jazz, to grunge and general rock. I listen to a lot of blues, jazz, folk music, classic rock, indie and alternative rock. I am particularly fond of female vocals. I generally tend toward cans that are relatively neutral/balanced, but I do have a fondness for clarity, and suspect I might have slight ‘treble-head’ preferences. I am not treble sensitive (at all), and in the past have really enjoyed headphones like the K701, SR325i, and of course the T1 and DT880. I have a specific sensitivity to the 2-3 kHz frequency area (most humans do) but my sensitivity is particularly strong, and I tend to like a relatively flat mid-range with slight elevation in the upper-mids around this area.

I have extensively tested myself (ABX) and I find aac256 or higher to be completely transparent. I do use exclusively red-book 16/44.1 if space is not an issue. All of my music is legally purchased (mostly CD – the rest FLAC purchased on-line). I tend to be sceptical about audiophile ‘claims’, don’t generally believe in burn-in, have never heard a difference with different cables, and would rather test myself blind on perceived differences. I am not a ‘golden eared listener’. I suffer from mild tinnitus, and at 49, my hearing is less than perfect (it only extends to around 14 kHz nowadays).

I’ve used the DAC Box RS mainly with my Linux PC System, primarily with the HD600, and mostly using either my LD MKIV OTL Tube amp, or VE's Enterprise tube amp (another review unit). I also used the DAC Box RS with my Windows 10 system and using digital DAPs as transports. For comparison purposes I primarily used my iFi iDSD – both as a competitive device, and also utilising it's excellent amp section to further evaluate the DAC Box RS.

This is a purely subjective review - my gear, my ears, and my experience. Please take it all with a grain of salt - especially if it does not match your own experience.

THE REVIEW

PACKAGING AND ACCESSORIES
The DAC Box RS came in a large white corrugated cardboard packing/shipping box measuring 300 x 387 x 153mm. Inside this was two perfectly fitting secondary boxes. The smaller contained the plugs and accessories – while the larger contained the DAC Box RS. Both were beautifully lined with heavy duty foam to ensure the unit arrives in pristine condition.

		[size=inherit][/size]
Very plain but appropriate packaging	The excellent foam padding	Very securely packed DAC Box RS

The full list of contents includes:

DAC Box RS
Power cord and AC/DC adaptor unit
Infrared remote control unit
Single sheet explaining front panel layout and rear inputs/outputs


Even the cords are well padded	The power cord and converter	Mini XLR power connector

My understanding is that normally there would be a driver CD for Windows use, but this wasn't included for the review unit. The Windows DAC drivers are easily found on Pro-Ject's website. All in all a little sparse as far as contents go – but functional. I would have liked at least to have had a USB cable included, but fortunately I had my choice of USB, coaxial or optical cables on hand.


Included documentation is clear	and very easy to understand.	The remote control

TECHNICAL SPECIFICATIONS & FEATURES
(From Pro-Ject)

Product	DAC Box RS – Digital to Analog converter
RRP	USD 1099
DAC Chipset	Dual Texas Instruments PCM-1792
PCM	Up to 24bit/192kHz asynchronous USB (XMOS technology)
Oversampling?	Up to 8X
PCM rates	2/44,1/48/88,2/96/176,2/192 kHz,(optical up to 96kHz)
DSD	Single or double DSD (up to DSD 128) over PCM
Filters	2 selectable digital filters (optimum frequency & optimum phase)
Balanced?	Fully balanced analogue audio circuitry
Freq Response	20Hz - 50kHz (+0/-1dB)
THD	0.005% solid state out 0.25% tube out
SNR	100 dB
Output stage	Selectable 6922 tube or solid state
Inputs	2x coax (S/PDIF), 4x optical ,1x USB B, 1x AES/EBU, 1x I²S
Outputs	RCA, XLR (balanced), Clock Out (for other Pro-Ject products)
Dimensions	205 x 200 x 70mm
Weight	1.01 kg
Casing	Anodised aluminium frame and casing

BUILD QUALITY / DESIGN
The DAC Box RS is a simple but elegant looking unit. The fit and finish is exceptional – very clean lines, and everything fits precisely. It looks as though it should be quite weighty, but is surprisingly light (1 Kg), but still give the feel of solidity and precision. The case has slightly rounded corners on the primary sides, and any printing is quite easy to read.


Left front panel on/off & infra-red	Input indicators and sample rates	Toggles to change input, filter and SS or tube

The front face (left to right) consists of:

on/off switch
IR receiver port
(top row) DSD indicator, then PCM sample rate indicator (44/48/88/96/176/192)
(bottom row) source input (1-9)
source selection toggle switch
digital filter toggle switch (steep/sharp or slow/optimum phase)
output toggle switch (tube or solid state)


Remote next to infrared indicator	Entire front panel	Corner view showing excellent fitting of panels

The LED lights are a soft blue and quite small. They are easy to see but at the same time are quite unobtrusive. The toggle switches are firm but also very stable.

The side panels are plain and just have a series of ventilation slots.


Entire rear panel	Closer look at inputs on the left	Closer look at inputs on the right

The rear panel from left to right consists of jacks and sockets for the various inputs and outputs. These are (from left to right):

(top) input 1 = USB connection (USB B socket)
(bottom) input 2 = sonic connector (for Pro-Ject products)
(bottom) input 3 = S/PDIF connector AES/EBU
(top) = power connector – 20V 3 pin mini XLR type connector
(top) = clock output (for Pro-Ject products)
(bottom) inputs 4 and 5 = two standard RCA coaxial connectors
(bottom) inputs 6 to 9 – 4 standard optical inputs
(top) R and L analog RCA outputs
(bottom) R and L balanced XLR outputs

So far I have tested only the USB, coaxial, and optical inputs – and had success with everything. For output, I have only been able to use the standard RCA analogue outputs as I don't have fully balanced topology to test with.


Side panels and ventilation	Underneath	Sitting next to my monitor

The power supply consists of a walwart, 20V/3A DC converter and cord which is long enough for the converter to sit on the floor while the power cable runs up to the DAC with plenty of length to spare (1.4m from plug to converter and another 1.4m from converter to power plug). One of my few issues with this unit though is the mini XLR power connector with this sample unit. It is very hard to remove (I think the actual jack is faulty). Not something to judge to harshly as I'm sure Pro-Ject would replace it with no questions asked.

All in all the externals are pretty much faultless – and a myriad of connection options. If there was one thing I would have loved though, it would have been a second set of standard RCA outputs, and the ability to switch or toggle between them. This would be ideal for someone with a dual amp set-up and perhaps might be a design option for Pro-Ject Audio to consider at some stage.

INTERNAL DESIGN
Taking a peak inside the chassis, the entire layout is very clean and quite impressive. The single main board occupies the entire floor area of the chassis. At the front left are the two 6922 tubes housed on two individual daughter boards.


Looking from front to rear	Looking from left to right side	Dual DAC daughter card

There are two ribbon cables – one from left front panel and one from the right front panel, both connecting to the mainboard close to center-right. These will house the IR circuitry, selector switch signals and of course the LED circuitry. There is a single large twisted pair of cables from the power input to the front of the board.

Apart from that the main board consists of mainly discreet circuitry, caps and transistors – very cleanly laid out, and unobstructed. To the right of the main board are 4 daughter boards mounted vertically, and these house some of the USB interface and also the actual dual DAC chips (so it is a full balanced DAC design).


Looking from rear to front panel	Looking from right to left side	Close up of the tubes on their daughter board

The DACs used are dual PCM 1792 which are among the best that TI produces and have exceptionally low noise and high SNR capabilities. They are capable of sample rates for PCM of up to 24/192, and also up to double DSD. Optical input is “limited” at 24/96. The dual DACs also have 8 x oversampling ability, and a choice of filters. At position 1 the filter is phase optimised (or sharp roll-off), and at position 2 the filter is frequency optimised (or slow roll off). The filters are applied for both PCM and DSD playback.

DRIVERS / USAGE / REMOTE
Windows 10
The DAC Box RS is pretty easy to set-up and use. For Windows 10 it was just a matter of downloading the driver from the ProJect website, a quick install, set the sample rate in the Windows mixer, and away you go. I also set-up Foobar 2000 for the DSD usage -both native and upsampling, and it was a pretty easy and painless process (helped that I had done it before). About the only issue I very occasionally encountered with Windows was that maybe 3 times so far I have booted into Windows and the DAC Box RS hasn't been recognised at all. This was a simple matter of a reboot to get it to reappear. More likely to be a Windows issue than the DAC Box RS – but I shall note it anyway.

Linux (Mint/Debian)
I switched back to Linux for my main system around 6 months ago – and it is now the environment I do most of my testing and reviewing on. The DAC Box RS is completely driver-less under Linux (they are already written into the kernel). It was recognised as soon as plugged, and the only thing I had to do (just once so it now stays this way) was run ALSO configuration and permanently un-mute it (thanks to Felix for helping me through this). For my audio player, I've been using J-River's Media Center 21 for Linux. I know there are free options – but I like the ease of use of upsampling, and it was a pretty cheap investment for such a good programme. I've had zero issues with Linux and the DAC Box RS, and for the last 3 months have often been rocking out with it, the VE Enterprise, and my HD600s.

Remote / Usage
Usage is simple with my Linux set-up. Boot up, turn the DAC Box RS on with the small remote which is supplied (with it you can control power, source input, and mute). The remote does have volume controls – but I'm guess that is for use with a ProJect amp in tandem. If you're going to be using the tube output – wait for the tubes to warm up, select source, choose your amp, plug your headphones and press play on your media player. I've tested the DAC Box RS primarily with the computers USB, but I also used an optical feed direct from my motherboard, and also digital out from my FiiO players (X3ii and X5ii). In each case, playback was flawless, and there was no issues with drop-outs or quality issues. Most of the time though, I've stuck with USB – simply because it has handled everything I've thrown at it from redbook to DSD.

MEASUREMENTS
My kit isn't good enough to measure high quality DACs. The limiting factor is my external sound card. Most of the DACs I try to measure simply have a noise floor lower than my sound card – so I end up effectively measuring my sound card. But I do use it for measuring an approximate frequency response, for measuring the effects of filters, and to at least take THD measurements (to check that there is nothing wrong)

Filters
I've engaged the filters and flicked them back and forth quite a few times trying to hear a difference between the phase optimised (or sharp roll-off) and frequency optimised (or slow roll off). If you're playing DSD, it is immediately noticeable, but that is simply because there is a volume difference between the two settings. For the PCM – they appear to be exactly volume matched, and although I've tried, I can't detect anything. Because my hearing tops out at 14-15 kHz, I suspect if there was difference I wouldn't notice it anyway. So I borrowed my daughters almost perfect hearing (she can still hear all the way to 20 kHz – which amazes me) – and she couldn't detect anything either. So onto the loopback – and using both tube or SS output, both graphs show almost identical output. Essentially you may hear something if your hearing is perfect (this could manifest itself in distortion) – but I think most of us will conclude that both filters sound the same.

Freq Response
Now if you've seen the first two graphs you're going to be saying “what's that roll-off!!”. Well its what shows on my equipment, and while I use is as an indicator, it may not be perfect. So I also measured the E17K's DAC – which I know is close to ruler flat, and also the X7 – which I know has a slow shallow roll from about 10K. On the same equipment and same settings, the DAC Box RS appears to roll off earlier, and also in greater volume. I have no reason to expect this measurement is false. As far as effective delta goes, my gear is showing a 10dB roll-off at about 16kHz or so. I'll talk more about this when I get to sound.


DAC Box RS vs X7 vs E17K	Filter comparison (close up)	Tube vs SS (close up)

Distortion
I know the DAC Box RS SS output measures below the capability of my sound card, so this experiment was simply to check and see if I could see the difference in the harmonic distortion between SS and tube output. And the measurements show this pretty clearly. The tube output had a SNR difference of about 10dB and a THD measurement one order higher. What surprised me though was how clean the tube setting measured. This is pretty impressive, and the noise floor does indeed seem to be around 100 dB down – eve on my inferior equipment.


SS distortion measurement	Tube distortion measurement

SOUND QUALITY (SUBJECTIVE)
The following is what I hear from the DAC Box RS. YMMV – and probably will – as my tastes are likely different to yours (read the preamble I gave earlier for a baseline). For my testing I've used a variety of headphones and amps – but for the completely critical test I used the E17K as amp (due its linearity), and also as a DAC for comparison for the same reasons. For headphones for critical listening I used the HD630VB sealed headphones – mainly because they are a benign load for the E17K, and also because they are a very good pair of headphones for evaluation – essentially having a pretty flat frequency response (once dialed in).
I choose not to comment on bass, mids, treble, and most definitely not sound-stage – simply because IMO when we are talking about an amp or DAC – they shouldn’t be discussed. An DAC's job is to decode the signal with as low distortion as possible, and output as linear signal as possible. If it is doing its job properly, there is no effect on bass, mids, or treble. And IME a DAC does not affect soundstage (unless there is DSP or crossfeed in play) – that is solely the realm of the transducers and the actual recording.

Tracks used were across a variety of genres – and most can be viewed in this list http://www.head-fi.org/a/brookos-test-tracks.

The DAC Box RS (via the linear E17K) is simply a really nice combo to listen to. With music I know really well (eg test tracks like Sultans of Swing) the measurable roll-off is showing no loss in detail, the opposite is in fact true. Detailing is crisp and clear, and I'm able to very clear hear the shimmery decay of cymbals and minute clicks and taps of the drum sticks. And I guess this may well be the low distortion at work because the lingering impression is one of a rich and well balanced sound signature. The DAC is in effect getting out of the way and allowing the music to shine.

Switching between tube and solid state, and there is a very slight softening in overall tonality, almost as though the top end has been rolled a little more. But there is no muddiness or masking when going to tube – this really is a linear output, and the differences are very small when flicking between the two. Emma notices a little more than me (her significantly better hearing in play) – she says one sounds bit brighter, but she prefers the tube output. Me – I can't really tell the difference apart from that very slight softening, and it really depends on which amp I have paired as to my preferences. With the E17K it is the tube output. With the LD MKIV or Enterprise, I usually switch to the SS.

With the right kind of music, it is very easy to lose track of what you're trying to concentrate on – and that for me says more about this DAC than anything else. Any device which helps me lose my way in the music is a good DAC.

COMPARISONS
Again this will be pretty subjective. I've chose to compare the DAC output against the E17K and also iDSD – using the E17ks amp output each time and sticking to the HD630VB. It's pretty hard to compare – as each change takes about 30 seconds, it is completely sighted, and subject to all of my limitations and bias.

DAC Box RS Vs E17K
It took me quite a bit of back and forth, and this should have probably been the easiest to pick – but the delays in switching took a while. The main difference between the two appears to be that the E17K simply sounds a little more crisp and brighter, where the DAC Box RS is tonally a little warmer and smoother. And the funny thing here is that despite loving neutrality, I'm drawn into the music just a little more with the DAC Box RS. There is again no loss off detail, but the presentation of that detail is subjectively presented subtly different. With the E17K its as if there is more of white light which is exposing any flaws, and the DAC Box RS has one of those slightly coloured “warm tone” lights – giving the same output, but a slightly more relaxed setting. As much as I love the E17K's no-nonsense presentation, I'm enjoying the DAC Box RS a little more.

DAC Box RS vs iFi Micro iDSD
This took me a long time and track after track. I had the iDSD's IEM match set to off, and filter set to bit-perfect. Like the E17K, the iDSD sounds slightly clearer, crisper, brighter – but this time it is a marginal, and the differences a lot more subtle. And I'm not really sure if the differences I'm hearing are there at all. The iDSD (to me anyway) sounds very similar to the DAC Box RS – and if anything that is a big thumbs up to the RS, as I happen to think the iDSD has a wonderful DAC. I get lost in the music frequently with both.

SPECIAL PAIRING
I would be remiss in mentioning the pairing that I have listened to a lot over the last few months. On the odd occasions I have had free time, I have combined the DAC Box RS with my PC (via USB), and then to the Venture Electronics Enterprise tube amp. Usually I use my HD600s, and the media player of choice has been J-River's Media Center 21. With the DAC Box RS, I can choose to run bit perfect, or upsample – and the nice thing is that I can do this without having to jump through hoops with daemon settings within the ALSA or Pulse stacks.

I know from my testing that the real magic with this combo has been the Enterprise itself, but the entire system matches extremely well together, and I have had more unexpected “wow” moments in the last 3 months with this combo than in the last 1-2 years. I could see myself calling it quits with a system like this. Its pretty close to end-game for me.

DAC Box RS – SUMMARY

My time with the DAC Box RS has been a thoroughly enjoyable one, and I should probably apologise to Felix for taking so long with it. I really appreciate his patience – they have never pushed me.

As far as build, aesthetics and size goes, the DAC Box is a premium little rack unit with a classy (timeless) simplicity which really appeals to the minimalist in me. Everything is well laid out and easy to read and control. One of the things I would pick at (and it could just be this unit) is the mini XLR plug (for power) being difficult to remove, but lets face it, most of the time you'll be plugging this unit and then forgetting it anyway.
Usage is easy, and it is quite versatile with the options of tube or solid state output.

The amount of inputs (9) is quite staggering and to be honest I wasn't able to do justice to full use of it – but as a DAC at the heart of a home media center the RS would be an ideal solution. One thing I would have personally loved to have seen would have been an extra set of RCA outputs and the ability to switch output between the two. I'm not sure if I'm the only one who would use two amps and like to be able to switch without swapping cables – but it might be something to consider. Oh, the DAC Box RS also has true balanced output also for those who need it.

As far as audio performance goes, it subjectively delivers a rich, smooth, but still detailed and highly immersive experience. Objectively the upper registers are rolled off a little – but it does not seem to detract from presentation of detail. At a retail price of around USD 1100, the DAC Box RS is not cheap, and for a straight desktop solution there will be cheaper options out there which may appeal more (especially as far as size goes). On performance, it was at least as good as my iDSD – but my iDSD is considerably cheaper, and contains a very good amplifier.

Where the DAC Box RS shines though is at the heart of a media system – and when our teenagers eventually leave the nest in another 6-8 years, this type of device is exactly the sort of unit I would be looking for.
So how to rate it? Well given I'd really like one (just not for my current needs), you can probably tell I really enjoyed this unit. For its intended use (which is more media-center oriented than desktop) it is an easy recommendation. Yes you can probably get cheaper solutions if you're on a tighter budget. But it doesn't stop this particular device being an easy 4 stars. The only real caveat is the price.

FINAL THOUGHTS
I'd just like to give a late shout out to Felix and thank him for the use of this unit. I'll try to get it back to the distributors quickly. Felix, if you have something with similar performance, but which combines a DAC and amp in similar form factor, I think it would be a fantastic desktop solution. I've loved every minute with this unit, and will be genuinely sad to see it go.

EDIT : Felix has contacted and they do have a combined unit (DAC/amp) - the Pre Box RS Digital, and for a cheaper option - the MaiA so I'll definitely be checking them out at some stage!

Reactions: zjx1017, pedalhead, Fearless1 and 7 others

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KDS315

Be aware that ONLY the XLR-outputs are volume controlled, the RCA outputs are FIXED volume!

B

Benef

KDS315 Jesteś w błędzie. W DAC Box RS wyjścia RCA i XLR mają stały poziom i nie można ich regulować.

B

Benef

Wyjścia xlr i rca są nieregulowane.

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Pro-Ject Audio DAC Box RS