Cambridge Audio 751BD

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Does this new player from Cambridge Audio set standards?  Noel Keywood applies the tests.

(a more comprehensive version will appear in our September 2011 issue, comparing it with the 650BD).


The Cambridge Audio Azur 751BD plays Blu-rays and DVDs, but is also strongly purposed as a simple stereo analogue CD player, one of good quality. It has stereo outputs on the rear, where the 650BD does not. Bolstering its stereo credentials are selectable audio filters that affect the sound at these sockets. This player plays DVD-As and SACDs and outputs DSD or PCM over its HDMI line to a receiver.


It can be used as a stand-alone SACD player but PCM must be selected in the SACD set up menu to get sound at the analogue stereo output sockets. Also on the play list are HDCDs and all DVD and Blu-ray music coding formats from Dolby and DTS, including the highest quality DTS HD Master Audio and Dolby TrueHD, both used in high quality movie sound tracks and even in dedicated music Blu-rays, such as those from 2L of Norway. These streams can be sent out undecoded (i.e. bitstream) to modern receivers or transcoded down to PCM to older ones, over the HDMI line. But again those who simply want better quality analogue stereo will get it at those stereo output sockets, high resolution digital audio being mixed down to high quality analogue stereo.


There are electrical and optical S/PDIF digital audio outputs and with these 751BD offers a very low jitter digital signal our measurements showed.


Also readable are USB ‘memory sticks’ with read-only sockets on front and rear, and the unusual addition of external Serial ATA connector so a computer disc containing video (or audio) can be connected. Cambridge say only WMA and MP3 music files can be played, not AAC from Macs. I should also mention that the handbook is comprehensive, succinct and easy to understand, unlike those of Far East players. This is likely to make quite a difference to getting the best from the player as there is a lot going on here.


An ethernet connection is provided, and a wi-fi aerial for wireless connection. I set light to my wireless router long ago so connected up by reliable, secure and fast wired link. It saw my Netgear router with a DHCP handshake without difficulty. Software update is possible and the hardware MAC address is declared so you can identify the player on a network.


Cambridge say only WMA and MP3 music files can be played over the network from a server, not AAC from Macs; I found WAV played too. Unfortunately, the player locked up a lot on my wired network and had to be reset often. As Onkyo receivers pass these tests with difficulty I suspect the 751BD could be better. Cambridge told me they are awaiting new software.

I could not get it to see an external 2TB, NTFS formatted, eSATA connected self-powered hard drive either, but Cambridge say they have experienced no problems here; this could be a disc formatting issue. It did however read WMV test clips over my network, but the network's data rate could not support MPEG video which stuttered then crashed the player. Because a restart takes 30 seconds this was time consuming.


The 751BD has two HDMI outputs, to run two monitors or a 3D set-up Cambridge say. I used the Output 1 which has a Marvell QDEO video scaler to bring DVD up to Blu-ray resolution. This worked well, our Burosch DVD test discs showed; even if resolution cannot be improved in theory DVDs look better in practice.

The player did a fine job with Blu-ray high definition video, getting through our HQV Blu-ray test disc without displaying any jaggies on the dedicated tests, nor in the video sequences (and film pull downs). There was no motion trailing nor any other visible blemish. Video shot on a Red camera on the Spears & Munsil disc looked stunning, but then it does on most players. My own test sequence in HD video (1440 Mpeg2 from a Canon HV30)) of a Tiger Moth biplane at Duxford airfield showed no blemishes, but contrast was set a little high for effect. The idling propellor produced a smooth blur, as it should (this motion can break up in some players).


Current Blu-ray players usually pass all tests on available test discs and in use picture quality depends mostly upon user adjustment and original video quality rather than the player’s electronics. The 751BD turned in a faultless video performance.

Load times were much like the 650BD, 27 seconds for the Java menu of John Meyer’s ‘Where The Light Is’ and 10 seconds for a normal menu, a relatively fast performance. Recordable BD-Rs and BD-RE’s were read without problem.



Both through the Marantz SR8002 receiver and a Creek OBH-22 feeding Quad II-eighty valve amplifiers to World Audio Design KLS9 loudspeakers (and Usher S-520 Surrounds with the Marantz), the 751BD was a tidy sounding CD player, if not a ground shaking step ahead in silver disc playing, at least of the CD variety. As with other Cambridge players I heard little difference between the filters and although our tests revealed clear differences in pre and post ringing with a raised cosine pulse, it was difficult to detect real life benefit. I slightly preferred ‘Steep’ for a little less sheen and a darker, purer tonality but differences are small. So don't expect too much from the presence of these filters; whether pulses pre or post ring is what engineers obsess about! I find harder roll offs at 16kHz, as in Chord's DAC64 and the new Audiolab 8200CDQ, more subtly useful.

As usual, between analogue, HDMI and S/PDIF (optical) feeds I preferred the latter for pure clarity, at least working into the Marantz receiver.


Both DTS HD Master Audio and Dolby TrueHD in highest definition 24/192 form were successfully read from Blu-ray music disc and sent out in native form or converted internally to PCM our checks showed, using 2L’s ‘Divertimenti’ disc that carries both, in addition to PCM. Results were impressive, but of course decoding takes place in the receiver in this situation. With 24/192 you get intense filigree detail and crystalline clarity, if not the silky smoothness of SACD; PCM always has a harder quality, even at maximum resolution.


I played a wide range of music from 2L at 24/192 resolution and the 751BD gave a full bodied and dense sound field with more texture than ordinary AV purposed Blu-ray players, helped by the ability to switch off displays on the player, as you can on Marantz receivers in Pure Direct mode.


Spinning live concerts like John Meyer’s well recorded ‘Where The Light Is’ (24/96) reinforced the 751BD’s solid sound, with plenty of heft to kick drum at the start of ‘Vultures’ and a clear bass line stepping along in the background.  The Who ‘Live at Kilburn’ is technically not  HD but a wonderfully restored time-piece from 1977 with high quality analogue video and audio for the benefit of an invited audience and the 751BD did a great job in getting the band’s energy across, Pete Townshend’s crashing guitar chords and John Entwhistle’s bass line at the start of Baba O’Riley thundered around my lounge impressively. The ‘751 told me data rate was a mere 47Mbps by the way, close to the limit for Blu-ray! The player’s firm digital grip on audio and good picture quality gave great results from this DTS HD Master Audio encoded video.


I suspect AV enthusiasts will wonder why Cambridge Audio charge double for a player that offers analogue stereo. It’s a good question. But you also get many other twiddly bits, like e-SATA input not available on the less costly 650BD and that would swing it for me as it allows computer stored high definition video to be played through the system without burning a Blu-ray or hooking up the camcorder direct.


As an analogue stereo CD player for serious audio use I wasn’t overly impressed, preferring quality from S/PDIF. But as a high quality Blu-ray player of tremendous ability able to play just about anything except LP, there’s little to touch the 751BD. It has a great performance, more ability and facilities than most players out there and a handbook able to explain it all in reasonably understandable English. And that is unique!


verdict five globes

Superbly capable player with extraordinary range of abilities and a great all round performance. An audiophile dream, but expensive.



Cambridge Audio

Tel: +44 (0)845 900 1230



- plays all silver discs

- solid, stable sound

- fine video quality



- dull styling

- small display panel

- erratic network performance



Frequency response of CD via the analogue outputs, shown in our analysis, was flat to 20kHz whichever filter was selected. Because there is no onboard DSD convertor PCM must be selected to output SACD, forcing DSD to be converted to PCM before going through the DACs. There was still benefit though, SACD frequency response reaching out to 32kHz before rolling away slowly, analogue fashion - see our analysis below. With high resolution 24/192 PCM the analogue outputs reached 48kHz (see our analysis below), so again high sampling rates are done justice.

Linearity of the onboard DACs was a bit below top rate CD players as is to be expected, since this is not a dedicated analogue player, but 0.29% at -60dB via the analogue outputs is still a good result and this allowed a good EIAJ Dynamic Range value of 98dB to be achieved. With high resolution 24bit PCM distortion dropped to 0.15% at -60dB (see our analysis below), against 0.02% or so possible, so there’s improvment over 16bit. Similarly, SACD gave 0.21% at -60dB so measured better than CD, and at -90dB just 0.6% - but DSD code is very linear at low levels, hence SACD’s smoothness.

Random jitter on the digital signal measured less than 20pS above 100Hz (see our analysis below). Signal related jitter was 80pS on a -60dB, 1kHz test tone, a very good result. There was a little low rate clock wander but it was not high at around 200pS maximum. All in all the 751BD was as clean in this area as the 650BD and will give fine sound quality through an external S/PDIF connected DAC.

The 751BD measured well through its analogue outputs and via its S/PDIF digital output. It provides audio of good quality. NK


Frequency response (-1dB)

CD          2Hz-20kHz

SACD     2Hz-32kHz

Blu-ray    2Hz- 48kHz


Distortion (%)

0dB       0.0008

-6dB      0.0008

-60dB    0.29    (24bit  0.15)

-80dB    3.8

Separation (1kHz)    108dB

Noise (IEC A)         -111dB

Dynamic range        98dB

Output                    2.0V


FREQUENCY RESPONSE, 192kHz PCM    (what it means)



FREQUENCY RESPONSE, CD    (what it means)



FREQUENCY RESPONSE, SACD   (what it means)



DISTORTION, 24 bit, -60dB     (what it means)



JITTER    (what it means)