My first contact with the brand name Stello was, when I tested the DAC DA100 Signature for “Audio”. Little time has passed since, and the company made a silent upgrade of the USB input, which now accepts signals up to 24/96. And this one of the few elements, that I pointed out in my review. Frankly speaking, I knew the owner of the brand – as it is the company April Music, and the Japanese from “Stereo Sound” went havoc about it. Their products seem to be nothing special – the most important product, Aura Note, is just another all-in-one system. But it differed from others with a splendid external design and fantastic sound. And an USB input, where they also pioneered. Despite this “Japanese” attention to detail, and all the mentioned before items, April Music, and their “hi-fi” brand Stello, are Korean, and not Japanese.

The tested system consists of a CD transport and a DAC. Both units are small, but splendidly made. Their external design is quite spartan, but they are graciously equipped. The drive is a top-loader, with a very readable display and many digital outputs, with an advanced circuitry driving them. The DAC is also top notch – with many inputs, switchable upsampling, RCA and XLR analog outputs. Both units can be connected with AES/EBU, RCA, TOSLINK and I2S. The last one is probably one of best ways to connect a drive with the DAC at home, but it is used surprisingly rarely. The I2S cable has five leads: Word Clock, Bit Clock, Data, Master Clock and the shield connected with ground. This means, that the clocks and control signals are transmitted separately, and not in packages with the audio signal, what results in a lower jitter. Still the left and right channel are transmitted together, but still the improvement of the sound is significant. And that despite having a well designed receiver circuit. I’ll just add, that the “100” series features also the HP100 – line preamplifier and headphone amplifier and S100 – a power amplifier.

SOUND

Discs used for testing:

• Handel Operatic Arias, Emma Bell, Linn Records, CKD 252, FLAC 24/96.
• Ben Heit Quartet, Magnetism, ACOUSENCE records, ACO80108, FLAC 24/192.
• Diorama, Child of Entertainment, Accession Records, A 119, SP CD; review HERE.
• Freddie Cole, „Waiter Ask The Man To Play The Blues”, Dot Records/Verve, DOT DLP 25316, CD.
• Geminiani, Sonatas for Violoncello & Basso Continuo, Alison McGillivray, Linn Records, CKD 251, FLAC 24/96.
• Handel, Messiah, Dunedin Consort & Players, Linn Records, CKH 312, FLAC 24/88,2.
• Jean Michel Jarre, Magnetic Fields,Epic/Sony Music, 488138 2, CD.
• John&Vangelis, The Friends Of Mr Cairo, Polydor/Universal Music Japan, UICY-9376, CD.
• June Christy, Something Cool, Capitol/EMI Music Japan, TOSJ-90033, HQCD/FLAC.
• Kings of Leon, Only By The Night, RCA/BMJ Japan, BVCP-40058, CD.
• Laurie Anderson, Homeland, Nonesuch, 524055-2, CD+DVD.
• Mills Brothers, Swing Is The King, History, 20.3039-HI, 2 x CD.
• Pink Floyd, London 1966/1967 EP, Highnote, PUC66, FLAC 16/44,1.
• Sakuro Ogyu Trio, Ballad Night, Carnival/BMG Japan, BVCJ-37532, CD.

Japanese versions of the discs available on CD Japan

Stello did not win my heart immediately. As you can see it finally did, but first it had to tell me its “story”. Like I mentioned earlier I tested the DA100 Signature DAC before, for “Audio”. The new version should differ from the old one only with the USB receiver, but I have the impression, that some other adjustments were made to it. Or maybe together with the transport, with the signal sent via the I2S bus, it sounded that way? I do not know, I did not have the older version to compare, so I can rely only on my memory. There are different theories about short term memory and others, especially with regard to music, but I rely on my experience and long term observation of musicians, conductors, composers, etc, who had the incredible ability to remember even the smallest details of expression, sonority, etc. I have seen a similar effect in myself, although on a different plane – I sometimes do not remember the symbol, name or looks, but I remember well my impressions, which accompanied the listening session. And even taking into account the changing personality of the listener (in that case me) it does not prohibit – in my opinion – to diagnose in a sufficient way the similarities and differences between devices listened in some time.

Being after the listening session I can say, that the Stello has a very pronounced personal character, correcting the sound in a clear way. So description was not difficult – the problem was to evaluate what we heard, interpret it and relate it to the price. The Stello sounds mostly with the midrange. The treble is withdrawn, and the bass not so dynamic as in the reference system. But this is not a warm sound. Much warmer sounds for example the player ISEM eGo, tested in this issue of “High Fidelity”. Initially this threw me off track, because usually, when the midrange is favored, then this is usually related to warming of the sound, and “pushing” out the midrange is the result of this distortion. Here it is different. I started the session with two discs - Only By The Night Kings of Leon and Magnetic Fields Jean Michel Jarre. The first one is a classy, splendid rock sound, the second – electronics. Both were reproduced by the Korean player very nicely, but it was immediately clear, that the sound is not overly dynamic or resolved. Everything seemed OK, but the percussion hits of KoL, and the low passages of Jarre’s synthesizers, were softened, and not so perceivable, not so physical, as from my reference system, but also not as from other, inexpensive players, like the Cambridge Audio Azur 840C, to which I will return later. You have to know, that Stello will not reproduce the bass in such a way, that it will represent the might of a live concert, or to create a higher pressure, that would influence the whole body, and not only the ear.

Like I said, I was off track, because I thought, that the DAC itself, with another drive, sounded more dynamical, that the disc Big Band Chet Baker sounded stronger, fuller. To verify this, I connected the CDT100 and DA100 with the concentric (S/PDIF) cable. I chose a quality cable for that, one of the best digital cables I know, the 7N-A2500 Mexcel from Acrolink – the same I used for the tests of the DACs for Audio. And then I started to understand, then I got what it is all about. The S/PDIF link had a softer, more washed out sound than the I2S. I am just after exchanging correspondence with one of the readers – very interesting for me – who addresses digital transmission differently to me. To make it short – he claims, that a well made receiver, with re-tacting, etc, can handle any jitter, regardless of the way the transmission is made. I respect this opinion, this is solid engineers knowledge, but I have a completely different opinion on that topic, and Stello provided me with more arguments. Looking at the inside I know, that the receiver part is really splendid, starting with anti-jitter circuits, and ending with splendid clocks. Now because the transmitter part is also splendid in the Stello, I assume, that everything is OK on both sides. I can be wrong, but have to rely on something. And in direct comparison between the S/PDIF and I2S, the latter wins without problems. The sound is fuller, lower, better focused and with deeper stage. I was struck first with the slightly trembling edges of instruments from S/PDIF. It was not bad with this connection, I liked it, but it was enough to have one listen with the I2S cable, to not to return to the first one. And what would happen, if the I2S was a classy cable? Like the one used in the Stello test by Srajan Ebaen in “6moons.com” (HERE)? I can only guess.

I didn’t devote so much time to the links by coincidence – switching from one to the other was going from hi-fi to the introduction to hi-end. I told you in the beginning, that I had problems interpreting what I hear – and it was mostly because I needed to set that back against the price of the device. And this price places it next to the fantastic CD-07 Ayon Audio. And it is a tough contender. But it turned out, that there are different niches in the market, and the Korean system exploited it brilliantly. This is not such a dynamic and expansive sound as from the Ayon. In longer listening sessions, in more expensive surrounding, its sound seems more balanced. Ayon is superb with everything up to a dozen thousand zlotys – there it is the champion. The Stello offers a deeper insight into the musical pieces, more balanced. So we can choose what suits us better. Like I said, the most important aspect of the sound is the midrange. The vocal of June Christy from the disc Something Cool had splendid dimensions and volume. Although the pressing technology of the disc I have – HiQualityCD – goes in that direction, supporting the players, Stello used it potential splendidly, what does not happen so often. The modulations of her voice were nicely audible, her breath, etc. I also liked the presentation of the brothers Mills from the disc Swing Is The King, because despite it being mono recordings, they had depth, the voices had a clear edge and were shown on the background with instruments and the noise of the shellac disc, from which the recordings were copied.

The bass was deep and full, but had no “stiff” attack, it had a slightly rounded front. But because the midrange was most important, you did not pay attention to that part of the sound spectrum, at least not as much as you should. Ayon and Cyrus CD6 SE show the contrabass in a clearer way, they play with it, underlining it. The Stello seems to be more balanced and will not draw attention to the bass. Please understand me well – I am not talking about the withdrawal of this subrange. The sound is quite full and deep. The strong rock of Kings Of Leon had a nice breath. This was not fully “hardcore”, but it is not always the goal of listening, and not everybody will like that.

The Stello sounded very nice, very competent. But it was audibly worse than the – five times more expensive - Lektor Air Ancient Audio. The differences were mostly in terms of resolution, clarity and differentiation. The more I was surprised when I listened to the Korean system with the Leben CS-300 XS (SP) and the Sennheiser HD800 headphones. That was it! I was searching a long time for a device, that would not be overly expensive, and would be a worthy partner for that amplifier. Now I have it – the Stello sounded brilliant with headphones! Really not much worse than the Lektor. Well, maybe much, but it was subjectively different. It was mostly about a climate, this device could generate, the depth and breathtaking sound stage. I really liked it much. And it is not only about music. During the test, I started to view the first season of the TV series Stargate Universe w HD (2009, dir. Andy Mikita) using my Dune Prime 3.0. Because I have time for that only deep in the night (earlier I am preparing tests for “High Fidelity” and “Audio”…), I watch using headphones. How well did it sound! In the HD version the SGU sound is coded in AC3, so it is nothing special, but it still sounded incredibly well. Finally I made some tests with hi-res files and USB. Yes, it sounds like it should. The earlier version was OK, but it had all the limitations of old type receivers – weak dynamics and washed out virtual sources. Now everything returned to normal. It was still not the same as playing the files via S/PDIF (from the Dune), but the difference between those connections was not as big as I had expected.

DESCRIPTION

CDT100

The Stello devices are of the same size as the Cyrus, but are lower. Both are placed on small, glued on feet. Nothing special. Their enclosures were made from classic, bent sheets – the bottom one is steel, the top and sides are aluminum. The front panel is also an aluminum one. I must say, that this aesthetics is to my liking. It is simple and functional, while not devoted from a certain beauty. In the middle there is big, well readable display, red, and made on LED modules. Because it is bigger than in my Lektor Air, I appreciate it in a double way. To the right there are four small buttons operating the drive, to the left a standby switch and a button to read the TOC from the disc. Normally this function is handled by a microswitch in the tray, but here is no tray – this is a top-loader. I say even more – there is no classic cover, which could work the same way. This is the reason you need a separate button to do that – exactly the same as in my Air. In the Stello it is easier – this button is repeated in the remote control, something, that is not there in the Lektor. And this is a problem of the applied transport – the Stello uses a different one than in the Polish player. Let me just add, that there is a multitude of digital outputs on the back panel – there is AES/EBU using XLR, S/PDIF using RCA and TOSLINK and I2S using computer type sockets, similar to those for mice or keyboards. We do get a fitting cable in the package, although it does not look very well. The disc is placed directly on the motor shaft and clamped with a rather light puck, which has magnets inside, helping in securing it. The name CDT100 does not change, but the unit does. We received for testing the latest version, that differs in some minor details from their predecessors. The most visible change is the cover of the disc slot – now it is a wooden one, while earlier it was made from acryl with a metal handle. However, from my experience, it is best to leave it off while listeining.

After removing the top cover we can see very nice things inside. The drive is a Samsung one – very simple, but also quite solid. To decouple it from the environment it is not bolted tight to the enclosure, but placed on elastic elements. Its servo is placed on the back, below the digital PCB. And this circuitry is really very nice. As we can read in the company materials, the outputs are decoupled with transformers, which help in keeping the required output impedance. There is also a nice, thermally stabilized clock. To the side there is the power supply, with a small transformer and two different power lines for the drive and the digital section. The remote controller is ugly and not very handy. It can be used to dim or switch off the display. This is a system remote, so it can also be used to control the Stello amplifier. Interestingly the DAC does not react to the commands, and although the remote has a switch for changing the upsampling frequency, it does nothing, and you have to do it manually…

DA100 Signature USB 96/24

Because I prepared the description of this device for “Audio” I will use the same material (I see no reason for multiplying…). The full name of the Stello DA100 Signature is amended with “24/192 D/A Converter”. As you will see shortly, this is mostly true. But first a few words about its looks. The DA100 is quite big – although it has 1U height and only half the width of standard gear, the depth is significant.

On the front there is a knob, that changes the input, a green LED signaling locking, a button with a LED for activating upsampling and a standby button with a corresponding indicator. Upsampling value is indicated with a LED. If it is off – then the circuit is not active, is it green – 96/24, and is it red – 192/24. A mechanical power switch is in the back, next to the IEC socket. But before I go to the back plate, I want to mention the very nice font used for the logo and button descriptions. I noticed also a small, but very important difference between the old and new version of the unit – in the middle of the front panel we can read: 96/24 USB. The back is really crowded. Looking from left we see a pair of analog RCA outputs, using really solid, Cardas sockets, balanced analog outputs, with Neutrik XLR sockets and five digital inputs. We have AES/EBU, RCA and TOSLINK (both S/PDIF), USB and I2S. All sockets – including USB – accept signals up to 24 bits and 96 kHz. So we can clearly see, that this is NOT a 24/192 DAC. This last value tells something else – it has an upsampling circuit, which can convert the input signals to the 24/192 form, in which it is converted to analog.

When we take off the top cover, we’ll see a perfectly ordered circuit on a printed board. The signal is chosen with an integrated switch and runs to the front of the DAC for initial processing. The USB signal has a slightly longer path. We have here a modern USB receiver, using the DSP from Tenor, exactly the same as in the CD-2s Ayon Audio. Before we go further, I will just add, that the DA100 Signature does not have ASIO drivers, what can be a problem when using the Windows XP operating system. There will be no problems with Vista or Windows 7, however.

I talked about the initial processing of the digital signal. Behind the power supply, close to the front panel we have a very worked out digital section, with two splendid, mechanically and thermally protected clocks – one for the 44.1kHz frequency and its multiplicity, and one for 48kHz and derivatives. However on the input we have the AKM AK4117 IC. Interestingly, this is a 24/192 receiver, so the limit of the Stello input to 96kHz must come from different considerations. After the receiver there is an asynchronous upsampler Analog Devices AD1896, with 128 oversampling, changing every input signal to 24/96 or 24/192. As you know from the front panel, it can be bypassed. The heart of the DAC is the AKM AK4395 converter, a delta-sigma 24/192 unit, with 120dB dynamics. From there we go to the analog section, which takes over about a half of the insides. It is built using integrated circuits, with one notable exception – the output circuit, working in class A and using big transistors in push-pull setting. On the balanced output there is a single chip working as a driver for long connections. The power supply is built around a medium sized transformer with two output sections – one for the digital and one for the analog part of the DAC. It is accompanied by Nichicon capacitors. The PCB is extremely solid, with gold plated traces. Comparing it to other devices you should note the output voltage being slightly higher than the standard – 2.4V.

Technical data (according to manufacturer):

• Dynamics: 110dB
• Digital filter: 6. order
• S/N: 120dB
• Distortion: 0.003% (at 10kHz)
• Frequency response: 10Hz – 45kHz
• Output voltage: 2.4Vrms
• Receiver: up to 24 bits and 96kHz
• Dimensions: 212(W) x 55(H) x 290(D)
• Weight: 3,5 kg