Cambridge Audio Azur 851E Preamplifier & 851W Stereo Power Amplifier Review

Separates have a certain cachet in the audiophile world; yes, we recognize that you can run a stereo from an A/V receiver, but in many circles you’re simply not considered serious about music until you make that leap. There are various reasons for this, the most relevant being that the amplifier sections in most receivers can’t match a meaty external amplifier in output capability, particularly into low impedance loads. Naturally, the logic then follows that if separates are good, the flagship models from an esteemed manufacturer like Cambridge Audio must be the key to audiophile nirvana. Enter the Azur 851E preamplifier and Azur 851W power amplifier. Priced at $1,849 and $2,499 respectively, Cambridge is claiming to offer audio purity along at a reasonable price. Curious to see what’s underneath the hood of the Azurs’ understated chassis? Keep reading (and watching)…

Cambridge Audio 851 Separates Video Review

Azur 851E Stereo Preamp

Cambridge Audio’s line on the Azur 851E preamp is that it delivers so little harmonic distortion and noise to the signal, they can barely measure it. As you might guess, rated THD is vanishingly low at <0.00045% at 1kHz, while the unweighted SNR is rated <110dBr, <90dBu. The 851E also puts out excellent numbers in terms of crosstalk, rated at >110dB at 1kHz, and frequency response, specified at 10Hz-100kHz ±0.1dB. Output capabilities are also substantial for a preamplifier, stated to be 8V RMS via unbalanced RCA outputs, and 8V+8V RMS from the balanced XLR jacks; for those keeping track, this is more than adequate to drive any power amplifier on the market to full power.

In terms of connectivity, the 851E is an analog only creature. A total of eight pairs of analog inputs are provided, three of which can utilize balanced XLR connections. As implied earlier, pre-outs include unbalanced RCA and balanced XLR jacks, and a subwoofer output is also provided. The 851E does offer some semblance of bass management, with the option to apply a 12dB/octave filter at 200Hz; unfortunately, this is a bit too high in frequency to be of much use. Typically, subwoofers are crossed over around the 80Hz mark using a steep 24dB/octave filter to minimize the possibility of localization.

Azur 851W Stereo Power Amp

Looking to the brawn of the operation we find the Azur 851W, a two channel amplifier capable of delivering 200W into an 8 ohm load (500W bridged), 350W into 4 ohms (800W bridged). The first thing one is likely to note about the 851W is that it’s touted to be a “Class XD amplifier”, which Cambridge claims to eliminate crossover distortion like a Class A amplifier while retaining the efficiency of Class A/B. While it sounds fancy, glancing at the literature it appears that “Class XD” is simply a good old fashioned Class A/B design which operates in pure Class A mode under low demand conditions.

In terms of rated performance, the 851W appears to be clean as a whistle, much like its preamplifier sibling. THD is rated at <0.005% from 20Hz-20kHz, with unweighted SNR specified at >90dB with 1W into an 8 ohm load. Frequency response is rated from 5Hz-80kHz, though no tolerance is provided, limiting the utility of the specification. Similarly, damping factor is rated at >110, but the spec is provided at 1kHz as opposed to a more useful range like 20Hz-500Hz. Last but not least, input sensitivity is rated at 1.5V RMS unbalanced / 1.5V + 1.5V RMS balanced, which as noted above, will be no problem for the 851E.

A Few Thoughts

Going down a spec sheet is all fine and good, but what did we actually think of this duo? Aesthetically speaking, the silver units we received look amazing (the 851’s also come in black). A remote is provided, though it does have much functionality outside of volume control. Most of the buttons on it are designed to control other Cambridge Audio devices. One oddity we found was that the Source Direct button, which was supposed to switch the unit in and out of Direct mode, instead toggled source inputs.

Of course, in the end, it's all about how these separates sound. Noise floor, as the measurements promised, was non-existent. We connected the Azur duo to a number of speakers including the Aperion Audio Verus Grand towers. Unsurprisingly, they powered the Verus Grands effortlessly, with no hint of distortion or clipping regardless of volume level. One thing worth noting is that the Azur 851W runs very hot. Most of the press images from Cambridge show the amp on top of the pre-amp, and that is with good reason. After moderate listening sessions (just an hour or two), the combination was very hot to the touch. You'll want to make sure you give these plenty of ventilation.

Conclusion

For some folks, receivers are great; for others, it’s a dirty word. If you fall into the latter camp, Cambridge Audio’s Azur 851E and 851W might be right up your alley. Naturally, offerings of this caliber aren’t inexpensive, though we wouldn’t qualify the total price tag of $4,350 as stratospheric either. Both specified and real world performance live up to the promises made by Cambridge, namely freedom from noise and distortion. There are of course a few foibles: we’d like better low pass filter for the subwoofer output as an example. However, for those looking to build a top shelf two channel system, there’s little doubt that the Azur 851E and 851W will both look and sound the part.

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.