Talk about Graham Slee and you think of small phono and headphone amplifiers of excellent audio quality, if perhaps unadventurous looks. But, and many of you will know my BBC background, I remember spending many a lonely night working in Bush House sitting in front of one of the mixing desks he made whilst working as senior engineer at Audionics. In those days the BBC ushered quality and precision. Graham Slee has continued that zest for making the best since then, with his own projects under the label GSPAudio (Graham Slee Projects) with a particular emphasis on trying to get the finest possible designs using big discrete components into the small spaces. I remember all the worries he had in trying to get great audio after RoHS changed permissible chemical elements used in electrical components – including the ban on certain components and lead solder. Following that ban, despite no vicars dying due to the lead on their church roofs or Miss Scarlet dying from the lead piping in Cluedo, political correctness massacred a great deal of great audio designs. Slee frantically modified components in order to get the best possible sound whilst China could still import whatever chemical cocktails they wanted. Mr Slee never gave up trying to get a triangular peg into a square tube, and his modified electronics went as far as they possibly could to get that good sound. By the way, the idea of trying to fit a triangular peg into a square hole is something I will be returning to again later.

Since their inception in 1998, GSP Audio have continually worked on new ideas and new avenues to extend their portfolio, including improved versions of a same product and also completely new avenues such as a power amplifier, interconnect and speaker cabling, and the Bitzie and Majestic DAC, the latter which I am looking at here. At £1600 this is their most expensive and the most recent product, and largest, though at only 17.4cm x 5.7cm x 18.8cm, it is still anorexic. Packing in 3 coaxial and 3 optical digital inputs these both operate 16 and 24 bit and up to 192 kHz maximum on the coax and 96kHz Toslink optical (to be precise, frequencies allowed are 32 kHz, 44.1 kHz, 48 kHz, 88.2kHz, 96 kHz and 192 kHz). Optical input 1 can be 192kHz to special order. There is also a USB and an RCA analogue input to boot. More on these later. The unit uses the professional and highly respected Wolfson WM8804/WM8741 stereo chipset and all with a 140ps jitter, the same as on my Cambridge Audio 650C Azur CD player, which uses the Wolfson WM8740 chip. Outputs include balanced through TRS 1/4 inch jacks ideally to be connected to the balanced inputs of their Proprius monoblock power amplifiers, and a fixed-output line-level RCA connection (though this can be supplied variable level at special request). To ensure a smooth and detailed analogue sound the D-A converter is run below full scale to prevent signal clipping. It is also run in hardware mode so there is no microcontroller adding its own signature through power supply modulation or interference. Its mute function is deprecated to a manual front panel switch to remove another layer of complexity, though this does mean I have to press it to delete digital clicks every time I switch tracks or change input. The DAC uses a digital oversampling filter sending the Nyquist frequency to 364 kHz, thus allowing for a gentle roll-off and a more natural sounding analogue low pass filter. More about roll-offs later.

At first listening I set it to analogue input. Slee included an analogue input predominantly for phono, which makes me think this product would be more sellable (certainly at this price point) if it were simply a phono input, since his own phono-stage designs could easily be incorporated inside the box. For the review I connected a CD player, similarly spec’d Cambridge Audio 650C Azur. I then plugged in the separate power supply; there is no on-off button, typical of all Graham Slee products, and something I do feel a missing element especially with pulses making their way to the speaker cones. Slee suggests you leave it switched on all the time to keep components at their optimum, and so for that reason there is no switch. I used the designated Proprius mono blocks, again without on-off buttons, connected via Slee TRS stereo 1/4 inch jacks (being balanced output there are 3 connections, hence the stereo jack). I also used a stereo jack-to-XLR cable to allow direct connection to my balanced Krell KAV250a poweramp input. I was immediately impressed by the quality of sound attainable from my Cambridge Audio. Analogue output was by no means an afterthought in this preamplifier. There was full bandwidth of frequency, exceptional warmth in the lower frequencies and a very quiet noise floor. Through my LS5/9 speakers from similarly named Graham Audio, the class-AB Slee Proprius gave a rendition with aplomb, an old school rendition that is very easy to listen to and very musical at the same time. This is a good combination. The volume control is labelled in dB, which I have always wanted to see on an amplifier or preamplifier, but which is very rarely applied. At -30dB or 9 o’clock, there was sufficient audio level even into the 25watt Proprius.

Once I switched to coaxial digital input things got even better. The speed and detail of sound was further improved, though the lower frequencies are not over emphasised, as they are slightly from the analogue output. The bass warmth from the analogue output was highly tempting, and very enjoyable. In comparison the digital was as clear as glass and open. This was not a complaint. Where the analogue was like Irish stew and dumplings the digital was just salad; much better for you but not quite so much fun! Once my ears got adjusted there was no going back. Unfortunately politics denied me to connect digital output from my SACD player. And similarly, whilst I could connect my Tivo box optical connection and get very musical audio from Radio 3 on channel 903 with bit rates of 192kbps (one of the best I have ever heard radio, I might add) and alternatively OTT compression on Classic FM on 922, HD audio at 256kbps wouldn’t be able to work. It would have been nice to watch the Proms in HD and get decent audio as well. Never mind. There are no politics with analogue.

For me to listen to my super dooper digi delights I would need to play the HD audio from my laptop. There is one problem with that. Most PCs don’t have an SPDIF or optical output, relying instead on digital output forcing itself out of the USB socket. This is where everything gets either confusing, or rather, mis-confused. Let me explain. The USB socket is not designed for audio. And also, the chip doing the D-A conversion on the laptop does not understand USB either. With an external D to A converter, all the digits for that audio will be sent out of the USB socket into the external DAC to be translated into analogue music.   USB audio class 1 (UAC1) works at a slower speed than USB Audio Class 2 (UAC2). Bear in mind these are not related to whether your USB socket is rated version 1, 2 or the latest 3. UAC1 is standard on all Microsoft laptops, and its design limits digital audio to 24bit/96kHz. OSX and Linux have a native mode USB audio class two driver (UAC2) so they can cope past 32bit/384kHz. Some, including Slee, believe that with native components and drivers digital audio exits PC laptops at only 24/48kHz maximum. For that reason Graham Slee uses;

“…plain-honest 48k adaptive isochronous, and the DAC section uses oversampling (8x) to give a very similar analogue result without all the faffing about”.

USB is converted to S/PDIF and reclocked by a Wolfson WM8804 transceiver which sends I2S to a Wolfson WM8741 balanced DAC chip. Therefore in the Slee the USB input quite literally converts the signal so it can be handled exactly the same as all the other S/PDIF and Toslink digital inputs.

There are so many discussions on the internet forums about what actually exits the USB, whether it be 24/48 or 24/96, that even I got more confused at the end than I was when I started. However, after many hours (this review has taken me longer than most), I realised that my Windows laptop played 24/96, and for those DACs playing 24/192 you can install a suitable driver on your PC (and which usually comes with the DAC itself) to convert any USB from UAC1 to UAC2. Today USB is the future of digital audio whether from your PC or mobile phone via a micro USB OTG (on the go) cable converter. SPDIF and Toslink limit you to a fixed CD or DVD Audio spinner, and in today’s world of hard-disk sourcing these elder two are disappearing as quickly as DCC did. For Slee not to allow 24bit/96kHz is, I fear, a big mistake, whether or not he believes it is possible now. His belief that the limit from a PC is 48kHz is actually shared by many others. However, whatever the specification, with many new DACs appearing each month, limiting the product will not be helpful. The Cambridge Audio DACMagic100, for example, allows 24bit/96kHz without a driver from a UAC1 USB. And their minute £100 Dacmagic XS, the size of a matchbox, will even allow UAC2 if you install the supplied driver.

The best DtoA device is a single box, because it will have the lowest amount of ‘jitter’. This is caused when the master audio clock has timing errors from the information it receives. A well-designed one-box disc player places a fixed-frequency master audio clock right next to the D/A chip for the best possible performance. My 20 year old one-box Krell KPS20i CD player has an enviable jitter of 0psec and many new DACs have little more than that. The “adaptive” isochronous USB in the Majestic, means the clock in the D/A converter “adapts” to match the rate that the computer sends out audio packets. The Slee Majestic has a reasonable 140psec, exactly the same as that of the ageing Cambridge Audio CD player. In reality, jitter-induced timing errors create artefacts that audibly degrade the music signal.

USB files played through this DAC were extremely musical, with no apparent degradation of signal, nor losses in top end frequencies, and the 24 bit noise floor being used fairly well (theoretically there are 120dB, and this DAC read just under a 100dB). Ravel Piano Concerto in G (Julius Katchen, with Istvan Kerytesz conducting the London Symphony Orchestra) was very controlled with the piano sounding very real indeed, something that really surprised me in view of the hardly exciting specification. Similarly, J.S.Bach Concerto for Four Harpsichords (Karl Ristenpart, Orchestra of the Sarre) was very precise with no lack of control or clipping. Slee’s attempt to fit a triangular peg into a square hole was perhaps not in vein after all.

For me to take full advantage of the Slee statistics I would need, however, to record my excellent audio onto DVD Audio and play via S/PDIF through the Slee. Boy, does that sound musical. Top frequencies are tight and well controlled, as are the lower frequencies through my Krell/Wilson Benesch Arc and Torus duet. Resolution, detail and dynamics are excellent and this unit gives out a commanding feeling of authority and control. Classical, jazz and popular recordings are of equal musicality in terms of soundstage, speed, and pure openness and clarity. If you are happy with its limitations on paper, and no Bluetooth or wifi, then this machine is definitely something well worth listening to.  Its technical limits are in some respects its ace card. Just like the Legato Link “curves” adopted on many Pioneer CD players/recorders to make CD almost human, and the fact that some of the oldest CD players actually sound more musical than later ones as they weren’t trying too hard to be too clever in the processing. Some folk might consider that conversion circuitry for frequencies us mere humans cannot hear (ie anything above 20,000Hz and therefore anything above the 24bit/48kHz maximum) will only add their own artefacts, such as intermodulation distortion, to infect the audio quality in the bits we humans can hear. However, I know that even a trumpet has some very very quiet harmonics at 80,000Hz (see abstracts from authors such as James Boyk), and that even I can hear different frequency patterns from the same trumpet recording on a CD and on vinyl. The fact that the Slee makes grand pianos sound so amazingly lifelike makes me wonder what magic the Majestic is doing. It also made me wonder how many of those 24/192 downloads are actually that, rather than upsampled CDs or from master reel to reel tapes that have a 30kHz roof? Even using the frequency curves on some of my digital downloads show very little actually getting past 20Khz, which is of course no concern for the Majestic, since the DAC’s analogue output is limited to 11Hz-36kHz (-3dB) from Coax input and only 11Hz-20kHz (-3dB) from the USB. However, and I reiterate however, this DAC is one hell of a musical experience. It might sit miles behind others in terms of specification, but in terms of audio musicality it hits the same spot as do many of their other products, and many preamplifiers of considerably more cost. Plugged into the Proprius mono-blocks, it makes listening to music very enjoyable. And plugged into the Krell KAV25a Wilson Benesch Arc/Torus combo ‘Walking On The Moon’ by the Yuri Honing trio eschewed double bass authority and percussion with dynamics and bite. All frequencies were in control and fast. Wynton Marsalis ‘New Orleans Bump’ was more open and fun than I have heard it in a long time. Even the analogue input from the Cambridge Audio CD player gave a very respectable rendition. Dee Bridgewater was only very slightly not in control in her loudest yells in Cotton Tail, but the bass line was full and I was in the audience. No, I was in with the musicians. I was that close to the details. This DAC-come-preamp thingummy could handle almost anything I threw at it as long as the digits were no higher than 24bit/48kHz. Whether you can live with this disability on paper is up to you, but if you want to hear pure musicality then this is a surprisingly good competitor. In terms of audio sound quality this DAC was one of the most enjoyable for ages.

Conclusion. For £1600 you might not get all mod cons like 24bit/192kHz USB, Bluetooth or wifi, and it may well not look as exciting as some at the same price or cheaper, but this DAC is not intended to be a Bugatti Veyron. This is a Rolls or Bentley with real wood veneer not carbon fibre, and super soft suspension, not spine shattering hardness. This product oozes quality and musicality with a useful analogue input thrown in. Yes, there are cheaper DACs out there, but this one is musical where many out there might just be telling you fibs.

Janine Elliott

Sound quality 8.45

Build quality 8.3

Value for money 8.2 (in terms of sound quality/£)

Total 8.28