Product: @-tunes music streaming device
Manufacturer: @-tunes - UK
Cost: 1000 GBP - 1500 €
Reviewer: Nick Whetstone - TNT UK
Reviewed: March, 2007

I recently reviewed the Trends Audio USB audio converter and was quite impressed with the quality of sound that can be obtained from a PC based audio system. So when I had the chance to hear the @-tunes SB+ streaming music player (hereafter referred to as the SB+), I jumped at the opportunity to see if PC audio could get any better.

Music servers have been around for a while now, probably the most popular being the Slim Devices Squeezebox, now in it 'mark 3' version, the SB3. There have also been some modified versions of the Squeezebox, most well-known being those supplied by Bolder Cables and Red Wine Audio, although the latter is no longer available. It is tempting to describe the SB+ as a modified Squeezebox, but it is more accurate to call it a music streaming device, built using the Squeezebox interface (with the PC). That's because the SB+ really only uses the part of the Squeezebox that gets the music from the hard drive. The rest of the unit, ie the parts that convert the digital data to analogue sound, and then pass that to the next part of the hi-fi system, is completely new. And to supply the new circuitry, there is a very high quality power supply system with separate (multi-stage regulated) supplies for each section of the SB+. Of course, all this extra circuitry won't fit in the highly compact original casing so the SB+ comes in two new housings. All this results in a product that is much more an @-tunes product, than a (modified) Slim Devices Squeezebox!

So what exactly do you get with the SB+? Well, the first thing you notice is the attractive housings, with their smoked glass front panels. There is one case for the SB+ itself, and another for the separate power supply. This is not the original PSU but something completely new, designed and built by @-tunes, and using the very well-known, and highly respected, ALW regulators. More accurately, the regulators used are a development of the ALW/Jung regs, rather than being actual ALWSRs. Inside the SB+ player, the DAC chip has been upgraded, as has the power supply to the DAC. The original output stage is dumped, and in its place goes a new circuit. Finally, the SPDIF output is also upgraded using RF techinques, transformer isolation, and a 75 Ohm BNC connector (rather than the more common non-75 Ohm RCA).

To use one of these music streamers, you must have a personal computer (PC), with your CDs ripped to a hard drive. You connect the PC to the streaming device using either a network crossover cable, or a wireless connection (wireless router). It is generally considered that the wired connection gives superior sound, although the wireless connection is probably much more convenient. For this review, I used a cable as I don't own a wireless router. The cable I used is 10 metres long, allowing the computer to be situated well away from the hi-fi or the listening position. In fact, having made my 'music server' PC as quiet as possible I can hardly hear it when it is in the same room. And when I put the server in my hall, just outside my lounge, I just forgot about it altogether!

Originally, Patrick Dixon of @-tunes came to see me with his own music server and SB+, and I had a brief listen. Unfortunately, that morning I had hastily connected up my speakers with one of the drivers out of phase so it wasn't the best of tests. However, it was enough for me to realise the potential of the SB+ and agree to write a review. With speakers set up correctly, and my own music server in place, I looked forward to putting the SB+ through its paces. Patrick kindly helped me set up the network connection, and gave me some tuition on using SlimServer. As ever, these things look much more complicated than they actually are. But it is fair to say, that getting all this set up, particularly ripping the music to the hard drive, is a bit of a learning curve. So is it all worth the effort?

First impressions with the SB+ are of the large sound stage, it quite literally stretches from wall to wall! It's a three dimensional sound stage with good depth. The performers and instruments are quite solid and stable, and well separated. Listening to familiar material, I once again found myself hearing certain lyrics that had eluded me in the past. I also heard small details for the first time, like the sound of a finger moving across a guitar string. On one track with an Irish singer, I heard her sing the word 'throwing' but pronounced with a 'T' sound instead of 'th'. The clarity and detail are excellent. Timing is spot on, and bass is very solid. Emotion is also clearly conveyed, something that I expect of any 'good' hi-fi! Altogether, the presentation is best described as solid and impressive, perhaps just slightly inclined to dark and solid, rather than light and airy. To be honest, the SB+ clearly betters my much-modified Philips CD723 and will give any expensive CDP a run for its money!

There is a noticeable lack of grain and harshness with the SB+ and it is some way removed from the very 'digital' sound of some CD players. When you play loud, there are no nasty surprises, although as with all good hi-fi, it presents enough of the 'picture' at lower volume levels, that you don't feel the need to increase the volume to hear anything 'extra'.

I also tried the SB+ with an external DAC, well three actually! At first, it was difficult to hear much difference between the SB+ on its own, and when it was used with an external DAC. The Scott Nixon DacKit, used with the Burson buffer, came very close to the SB+ in terms of performance and sound. Listening for longer spells revealed a few differences, and does show the SB+ (through its analogue output) to be slightly superior to the DACs that I tried with it. A modified Behringer DEQ296 (when used with the Burson Buffer) was even closer to the sound of the SB+, more so when I used an earlier version of the SlimServer firmware.

Now we could be forgiven if we assumed that the ones and zeros come off the hard drive and go to the DAC (either the one in the SB+, or the external DAC) that changes them into a musical signal. And that there should be no way that a piece of software can make that signal change. But experimenting with different versions of the SlimServer firmware clearly demonstrates that not only is sound quality changed, but (IMHO) there is a flaw in some versions of the firmware that affects phase.

I first noticed the phase issue when I played the Roger Waters CD, 'Amused to Death'. This album is recorded with Q sound that enables the sound effects to 'appear' all around the listening room. But using the latest Slim Devices firmware, effects that I usually heard immediately to my left, ie on the same plane as my listening position, were instead manifesting immediately in front of the speaker. Nearly all the effects on the album were in a line, level with the two speakers. However, when I played the album while using an external DAC, the sound effects were restored to their 'proper' locations around the room.

It is reported on various forums that a particular version (V15) of the Slim Devices firmware for the SB sounds better than the others so I downloaded it, together with a useful piece of software called 'Squeezebox Firmware Selector' that allows us to easily switch between different firmware versions. With V15 installed, I tried the 'Amused to Death' album again, and this time the sound effects were played correctly. In addition, I noticed a slight tightening up of the bass, although overall the sound is not quite so 'smooth'. This makes some music sound better and some not so, although we are talking nuances here. However, my point is, if the later versions of the firmware don't play the Q sound effects properly, this indicates a phase problem, not absolute phase that could be rectified by swapping the speaker leads, but something that means the sounds are not played back correctly. This isn't apparent in the sound quality of the SB+ unless you are playing something with the Q sound effects, and when using the standard SB it would perhaps be nit-picking to mention it. But the SB+ is clearly an audiophile product and as such, this issue is something that potential customers should be aware of.

For now, I recommend any SB+ user using the V15 firmware. You appear to get the correct phase, and overall sound quality is neither better nor worse. The only other issue is the volume control which is not as good as with the latest version of firmware (I believe that it is more akin to a linear control than a log) but it's one of those things that once you get used to it, isn't a problem.

At first, the 'extras' like remote control went mainly unnoticed as I concentrated on the superb sound quality. But as the days went by, I found myself liking the convenience of remote control more and more. The supplier recommends using the volume control in the SB+ as this allows us to do away with an analogue volume control and/or pre amp. In practice, I found that the SB+ will work fine straight into the power amplifier. I tried using both the volume control in the SB+, a separate active pre-amp, and a passive volume control. I could hear no advantage in any one so my recommendation would be to go without a pre amp or external volume control as it is one less component (and set of interconnects) in the system. Things are slightly different with a DAC however! The 16-bit DACs that I tried were definitely better when the digital volume control in SlimServer was disabled, and a volume control placed between the Burson Buffer and the power amplifier. Patrick Dixon informs me that with 24-bit DACs, the digital output control works a lot better.

Next I played with the SlimServer itself. Apart from allowing you to select the music that you want to play, by album name, artist, genre etc, you can also select to have SlimServer play tracks at random, an excellent feature if you just can't decide what to put on yourself. This random mix can even be confined to certain genres. So you could, for instance, play a random mix of classical tracks, or restrict the choice to folk music, jazz etc. Watch out for some interesting segues too; at times you will swear that your PC fancies itself as a DJ!

If you like to keep track of your music collection, SlimServer will also tell you how many albums you have, how many different artists are featured, and how many songs (tracks) are on those albums. I'm sure that there are many more features just waiting to be found but perhaps I am already moving away from the review of the SB+ as a music playing device!

Don't forget, you will need a computer to use the SB+ with, PC, MAC, Windows, Linux, it doesn't really matter! But you will need to rip your music collection to the hard drive and this involves something of a learning curve as regards the software involved. But once you have the hang of it, it is not really difficult or complicated. It's a one-off job and although you will want to add new music to your collection occasionally, it only takes around 10-30 minutes to add a new CD (this depends on the CD and the speed of your PC). Take my advice though, get a second hard drive to back up your music, ripping several hundred CDs to a hard drive is something that you won't want to do more than once! It is worth mentioning that @-tunes also offer a ripping service if you don't fancy the job yourself!

Patrick Dixon was kind enough to come and demonstrate a basic SB3 along side the SB+ and it is quite clear that in standard form, the SB3 is no audiophile source! However, it is approximately one fifth the price of the SB+ so is the SB+ worth its asking price? The answer is a resounding yes. Remember the SB+ is hand built and not made on a production line in the Far East! You are getting two hand-made cases, most of the circuitry rebuilt, and top-quality components used through out. Even the umbilical lead connecting the PSU to the SB+ uses high quality multipole connectors not usually seen on domestic hi-fi! The sound of the SB+ does justify the higher price, in fact it is the best sounding PC audio device that I have heard to date.

In conclusion, I like the SB+ very much, enough to go out and buy one if I could afford too! After my encounters with the SB+, and USB audio converter, (and hearing a sound card based system) I am convinced that PC based audio is the way to move ahead. I can tell that with the SB+ I am listening to something very good, something that takes all the useful features of the Squeezebox and then improves the sound quality to an audiophile level. Is this the best music streaming device? I can't honestly say but I would be very surprised if owners of the SB+ thought about upgrading for a very long time!

If you are thinking about upgrading your digital source, do yourself a favour and try to audition the SB+ to. @-tunes offer a 30 day money-back trial and so far nobody has asked for a refund! The SB+ has every right to stand along side the best of CDPs. Even if you weren't thinking of an upgrade, I urge you to try the SB+. But be warned - you almost certainly won't want to return it!

So does this herald the end of the CDP? Twenty-five years on from the arrival of CD technology, there are still may turntables in use. But it can be argued that the sound quality of a good turntable is better than a CDP so its survival is no surprise! The same doesn't hold true for the CDP against PC audio sources. Of course, not everybody will want to rely on a PC to hold their music, and a CDP for them will continue to be the best option. Portable devices will continue to be attractive to those who have a large CD collection and want to listen to music on the move. But even the portable CDPs are under threat from MP3 players that are more compact, store more music, and are not so susceptible to the problems caused by sudden movement. In short, I reckon we will see a decline in CDPs now, with PC audio devices become increasingly popular amongst both the audiophile market, and those who just like the incredible convenience! Had it been a mass-produced item, perhaps the SB+ would have gone down in hi-fi history as one of those 'landmark' products that marked a significant change in our hi-fi systems!