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Cambridge Audio Stream Magic 6
Sound Quality
Conclusion
Measured Performance
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Cambridge Audio Stream Magic 6


 

FAST STREAM

 

stream_magic 6

 


With fast upsampling convertors able to handle full high-definition audio, the Stream Magic 6 Network Player offers massive performance at a great price, says Noel Keywood.

 

Network players are the latest big thing; new ones are tumbling onto the market in a modern electronic avalanche. With many coming from China and Taiwan prices are keen, Logitech’s Squeezebox costing just £200 or so, for example. UK manufacturers charge more, but you also get more, including a better user interface from Cyrus and Naim, for example with Naim offering top quality 24/192 resolution if you have pockets deep enough.

 

Cambridge Audio are in on this gold rush and they’re determined not to get left behind. First came the NP30 and recently the new Stream Magic 6 Upsampling network player was released. It offers top quality audio and a slew of natty options, at a price of £699 – below most UK and European manufacturers, if a little above Far Eastern product.

 

 

As a network player the Stream Magic 6 is designed to plug into a home computer network, so it can play music from computers or storage devices on the network, and also access the internet to get internet radio and streaming services. It will also play music files from a memory stick, sockets being available on both front and rear.

 

I prefer to use a high speed memory stick because it avoids a slew of jitter and noise problems, not to mention the limitation of computer music players like iTunes. However, the Stream Magic 6 cannot play 24/192 from a USB memory stick; 24/96 is the maximum quoted rate and my 24/192 WAV test file on a high speed LaCie Whizkey stuttered badly, being effectively unplayable.

 

Since at present 24/192 music files are uncommon this isn’t much of a imitation in practical terms, but I was surprised all the same, because on the test bench it was obvious that Cambridge have gone to some length to exploit high definition replay through the dual Wolfson WM8740 24/192 DACs, more of which later.

 

Because network players must turn digital to analogue through internal convertors, in order to feed an ordinary stereo amplifier, it is easy to elaborate on this arrangement and this is what Cambridge Audio have done. Not only are there phono socket analogue outputs, but balanced XLR outputs too for those that have an amplifier equipped with XLR inputs. Unsurprisingly, Cambridge Audio’s own amplifiers now come with a set of XLR inputs. Sound quality is usually better – clearer, a bit sharper and better focussed – than that of the usual phono lead. This is especially the case when leads longer than 1 metre are used.

 

Another elaboration is to add a digital input so the unit can be used as a high quality Digital-to-Analogue convertor and the Stream Magic 6 has both electrical and optical S/PDIF inputs. I see Cambridge Audio carefully quote a sample rate of 192kHz for the electrical input (via phono sockets), but just 96kHz for the optical input, when in fact our measurements showed both successfully handle 192kHz. However, a lot optical hardware still does not work at 192kHz so in practice making a connection via TOSLINK optical may not work, but not because the Stream Magic 6 cannot handle full data rate (9Mbps) through this input.

 

There are two S/PDIF digital outputs, optical and electrical, for those who prefer to use an external DAC and I tend to prefer to use a digital link in preference to analogue, in conjunction with a good DAC in the receiving amplifier. However, because Cambridge equip this player with a wide bandwidth, high quality on-board DAC, rather than a cheap get-you-by, it isn’t necessarily the best option. Analogue connection via the balanced XLR outputs may well sound better.

 

Although the Stream Magic 6 connects into a wired home network through the usual RJ45 socket at rear. it also sports a wi-fi aerial and will link through wi-fi, albeit with reduced data rate. However, another reason for wi-fi is to connect wirelessly to an iPad or iPhone so the unit can be controlled more easily from a settee. And this is useful, because as with most network players the on-board display is barely big enough to be legible across a lounge; I strained to read the unit much past 10ft away. With the free iPhone App however, I could easily sit back and dial up music at leisure, with only the ‘phone’s Passcode Lock constantly trying to deny me access to the hi-fi.

 

The App provides control of volume from the phone, if the Stream Magic’s digital volume control is selected in its Advanced setup menu. However, digital volume controls reduce resolution and are best not used if an analogue alternative is available. In one system I used, a Marantz remote control operated the Stream Magic’s digital volume control as well as volume on an SR8002 Marantz AV receiver, turning both down in unison, another reason for not implementing digital volume control.

 

As if all this was not enough Cambridge also add another option, a Bluetooth link using aptX or A2DP protocols. This allows music stored on a portable device like an iPad or iPhone, to be played wirelessly through the Stream Magic 6. Quality is limited to that from CD ( 44.1kHz and 16bit) because Bluetooth cannot currently handle higher data rates, but it is a nice, simple way of playing music. It took many attempts to get my iPhone 4S to pair with the Cambridge Audio BT100 receiver (they exchange security keys) but they decided to talk to each other in the end and then I could watch Sharon den Adel singing ‘Angels’ on my iPhone whilst listening to her through the hi-fi – oh heaven!

 

Control of volume is digital again, on the phone this time, and the Bluetooth link just streams music; it has no advantage over using the App and in fact has the drawback that it does not control the Stream Magic 6. It does, however, allow an iPad or iPhone loaded with music to play it remotely through the hi-fi.

 

Music can be streamed from a computer via USB rather than Ethernet, bypassing the need for a UPnP server. Connecting up a MacBook Pro laptop running OS-X 10.7.3 (Lion) the Sound output Audio panel came up with a 192kHz sample rate output option by default. This surprised me because I thought core audio was 96kHz sample rate maximum on a Mac. However, Cambridge confirmed it was not and a Mac can natively handle 192kHz, but a PC cannot. So I live and learn! To get a PC to send 192kHz sample rate audio via USB, Cambridge offer a free PC USB driver as a download.

 

When the USB input of the Stream Magic 6 is selected, no digital output is available – a pity. When USB Media is selected, however, a digital output is available.

 

From the Mac, the Trondheim Soloists played ‘Divertimenti’ in full 24/192 resolution (WAV file) without a hitch and the performance sounded richly textured and relatively smooth from what is usually a slightly thin and bright, if intensely detailed recording from the Blu-ray (I often use this recording when reviewing AV components like Blu-ray players and receivers). Experience is beginning to suggest to me that silver discs seem more prone to a bright and coarse sound than streamed audio and, since silver discs measure well from our specialised Philips and Rohde & Schwarz test discs, I suspect degradation of their sound enters in the mastering process. All of which suggests that modern computer based audio processed through devices like the Stream Magic 6 has more potential than that from silver discs, even if it does all seem fearsomely complicated at present!

 

Talking of quality brings me to the fact that the Stream Magic 6 Upsamples internally to 384kHz and applies a ‘polynomial curve fitting interpolation’ licensed from Anagram Technologies of Switzerland. This gives greater freedom in applying filtering and indeed Cambridge Audio exploit this by offering three different digital filters on the Stream Magic 6: Linear phase, Minimum Phase and Steep. I have listened to this filter set many times and can barely detect differences; my preference is always for the very slightly darker and more stable sound of Steep. And I’m pleased to note that our new Rohde & Schwarz UPV digital analyser shows there is truly little difference in either pass band or stop band behaviour of these filters, up to 250kHz, so my ears don’t deceive me! Having selectable filters is a nice touch, but don’t expect to hear big differences. The changes in phase and elimination of pulse pre-ringing are subtle effects.

 

Finally, internet radio was beautifully catalogued on my iPhone and an iPad is even better, making listening to internet radio easy. Countries are identified by their national flag and there are 203 of them. The UK comes up between Uganda and Ukraine – and even the Gaza Strip is represented. An alphabetical index down the side makes access quick and easy, to what totals around 14,000 stations globally. In most menu schemes internet radio is difficult to access, but via Cambridge Audio’s App it was a doddle. And there are Streaming services like BBC iPlayer Radio, Pandora and Rhapsody, some of which need registration before use.





SOUND QUALITY

Sound quality from 24/96 files played from my USB Whizkey was exactly as expected, with no addition or subtraction. Echo from around the drum kit and the snap of snare was beautifully displayed on ‘Misery’, from Dave’s True Story, a Chesky demo track. The Stream Magic 6 painted up a capacious sound stage; bass sounded solidly punchy but treble was delicate and detailed, gentle brush stokes on cymbals coming across with delicious presence. As usual there was no digital harshness or glare of the sort common to CD, and even Blu-ray.


stream_magic_6-rear-site



To emphasise this point ‘Divertimenti” from the Trondheim Soloists in full 24/192, played via USB from a computer, sounded full bodied, richly detailed and yet gently portrayed across the treble regions. Violins were clearly separated, one from another, and there was little of the monotonality, or loss of timbre, associated with digital. Upper frequencies sounded pure and sweet. What was surprising about this is the download file I was playing at full 192kHz sample rate via the Stream Magic 6 was much more convincingly balanced, meaning smoother, denser and less screechy, than the Blu-ray version I use repeatedly as a review test track. So it’s a track I know well and what I heard from the Mac Book Pro playing this file via iTunes was obviously better than the version I have on Blu-ray and, by the highest current standards, of utterly superb quality. I am finally beginning to like digital!


What was a little intriguing here is that with the Mac Book Pro set to 192kHz sample rate, the Stream Magic 6 flagged up 192kHz, even when 96kHz or 48kHz files were played. As Mac fans know, the Audio utility in OS-X sets a fixed output rate and up or down samples to it. This was the first time, however, I have encountered 192kHz as a fixed output option. Even 44.1kHz CD derived files were sent at 192kHz – but no, they did not sound better!  So ‘Stairway to the Skies’, a Within Temptation iTunes+ download (44.1kHz sample rate, 256kbps data rate) had Sharon den Adel singing from a somewhat muddled sound stage as usual, even when upsampled to 192kHz sample rate by the Mac and processed via the Stream Magic 6.


However, I also use many tracks from the Eagles album ‘Long Road out of Eden’ album, ripped from CD, as test material and these sounded cleaner than the original CD. The slowly sung ‘I Love to Watch a Woman Dance’ was purer via the Stream Magic 6, with less harshness than the CD and greater insight too. In other words, this CD at least sounded better when processed through the system and I can only suspect re-clocking and jitter reduction are the mechanisms responsible. Why didn’t the Within Temptation album The Unforgiving sound better? Probably because its sonic problems are different, lying within the original recording or AAC compression, neither of which can be lessened by subsequent digital processing.

I would not say there was more to be heard from CD, only that it was better balanced and more purely conveyed from the Mac through the Stream Magic 6.


Digital processing is a horribly technical and convoluted subject at present but the final results are very promising, fidelity wise. Classical music fans would drool over the Trondheim Soloists ‘Divertimenti’ download playing at full 24/192 resolution through the Stream Magic 6, for example.


CONCLUSION

The Stream Magic 6 is quite a box of tricks – and very easy to use from an iPhone or iPad communicating through a domestic wi-fi link. Only security passwording frustrates this process a little so it’s best to use an iPad that is not passworded.


The Stream Magic’s own display isn’t so great, being usable but not very friendly in its sequential layout, in comparison to an Apple screen. All current network players suffer this (Cyrus apart), but the Stream Magic 6 on-board display is still rudimentary.


Balancing this is a great range of abilities and enormous processing power, if with a few limitations here and there, like its peculiar inability to read 24/192 from a USB memory stick. However, performance of its on-board Wolfson DACs was superb and sound quality from the analogue outputs beyond criticism. I was taken aback at some of what I heard, such as full 24/192 replay from a Mac Book Pro. The Stream Magic 6 is a “must have” irrespective of my minor criticisms, it does so much so well, making great digital sound quality available at a very affordable price.

 

 

VERDICT

 

A complicated Network Player, but  one of wide ability and advanced performance. Great sound at a reasonable price.

 

 

FOR

- clean hi-def sound

- many inputs & outputs

- internet radio

AGAINST

- no 24/192 from USB key

- no digital output, USB in

- mediocre display panel

CAMBRIDGE AUDIO  STREAM MAGIC 6    £699


www.cambridgeaudio.com


 

upv-large-site

 

Rohde & Schwarz UPV audio analyser, used for all measurements.

 

 

MEASURED PERFORMANCE

Frequency response measured flat to 22kHz with a  48kHz sample rate test signal and to 40kHz (-1dB) with a 192kHz sample rate test signal from our Rohde & Schwarz UPV signal analyser, via both electrical and optical S/PDIF inputs. Our response graph shows a slow roll off up to 85kHz (-5dB) then a steep decline imposed by anti-alias filtering above 90kHz.

The three filter settings made little difference to this result, although Steep had a very minor effect, but it neither altered pass band nor stop band amplitude characteristics in any significant way (they alter phase and pulse pre-ringing). Output was free from spuriae up to 250kHz whatever filter was selected. The unbalanced phono socket output delivered 2.1V and the XLR balanced output 4.2V.


Distortion at -60dB was 0.22% with a 16bit signal, as expected, and 0.04% with a 24bit signal, both very good results showing the Stream Magic 6 is linear. Our distortion analysis clearly shows second harmonic predominates too, with 24bit resolution.


Noise was low with 24bit and Dynamic Range very high at 114.5dB, using a -60dB test tone notched out to lift output muting. In fact, noise sinks no lower with digital zero output muting, with 24bit, but 16bit quantisation generates 14dB of noise.


The Stream Magic 6 DACs resolve high definition audio fully, giving a very good measured performance in every area. NK

Frequency response (-1dB)       2Hz-40kHz

Distortion (24bit)   %

0dB                 0.0008

-60dB                 0.04

Separation (1kHz)               135dB

Noise (IEC A)                    -114dB

Dynamic range (24bit)         114dB

Output (phono/XLR)         2.1/4.2V

 


FREQUENCY RESPONSE, 24/192, S/PDIF

 

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DISTORTION, -60dB, 24bit

 

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