Just how much do we need to spend to acquire a decent integrated amplifier? A budget of, say £1,000, will net a large number of candidates. But if we also want bona-fide high-end sonic credentials, then the number of options becomes markedly smaller. Readers who have read my short bio here on The Ear will already be familiar with what a device needs to deliver in order to satisfy my ears – a balanced measure of each of the four key musical pillars; dynamic expression, dynamic agility, tonal quality and timing. The same goes if a device is £500, £5,000 or £50,000. No amount of casework bling, or backstory in which the company makes frequent use of the word ‘passionate’, cuts any ice. A device either supports the four musical pillars or not.
Even today when the art and science of audio design might be assumed to have advanced to universally lofty heights, we can still find devices which fail miserably in the four pillars test. Some of them boast test bench measurements so impeccable that they almost defy electronic science, yet they lack dynamic expression. This matters profoundly, because of the four pillars, dynamic expression is the musical quality that above all others tells our brain that we are in the presence of a live performance. Dynamic expression allows us to feel in our chests and our heads the air-compressing energy generated, for example, by the un-amplified human voice, a double bass, or a piccolo. Take that energy away and all we are left with is so much musical wallpaper; detailed and pretty perhaps, but ultimately uninvolving and unconvincing.
This is quite a different matter to volume or SPLs (sound pressure levels). Amplifiers that lack dynamic expression might still go very loud. And it’s certainly not about cost either. There are amplifiers with price tickets in the multiple thousands that fail the four pillars test. That’s why the Cambridge Audio CAX61 integrated amplifier and DAC comes as such a breath of fresh air. It has a retail price £100 less than our notional budget.
It’s an inoffensive-looking package, the CXA61; a matt pewter-grey box with a volume knob, source selection buttons and a 3.5mm headphone socket on the front panel. Around the back are four analogue inputs, plus S/PDIF, two Toslink and one USB socket. It decodes PCM up to 32-bit/384kHz and DSD256, and there’s in-built support for Bluetooth aptX HD too. Two sets of speaker terminals allow dual-room/four speaker operation and we also get a pair of pre-out RCA sockets, and a sub-out.
With the lid off, it becomes clear that it’s quite crowded in there. The amplification at the heart of this flexible package delivers 60 Watts into an 8 Ohm load. It’s technically a Class A/B design, but outputs all but the first few milliwatts in Class B, with current delivery of five Amps RMS and a peak of seven. The centrally located toroidal mains transformer is flanked by finned heatsinks that cool the output devices, while either side of the heatsinks are the amplification boards, one each per channel. At the back sits the digital board, logically, but not physically, centred around an ESS Sabre SE9010K2M DAC chip.
Design engineers normally get little credit for their work, and so I’m going to invite Cambridge Audio’s Stephen Tizzard to take a bow for his work on the CXA61. What Tizzard has achieved here, within the physical constraints of the chassis, and the boundaries of component and manufacturing cost set by Cambridge Audio, is noteworthy; a subjectively low-noise, low-distortion device that offers buyers a generous measure of high-end musical performance for not a lot of money.
Tizzard is clearly one who listens to the results of his design efforts and knows how to manipulate component choices and values to achieve a particular sound, in this case a well-judged and even balance of our four musical pillars. I fed the CXA61 analogue signals from a PS Audio Stellar phono stage and a Mola Mola Tambaqui DAC, as well as digital from a Jay’s Audio CDT3-MK3 CD transport via S/PDIF, and from a MacBook Pro via USB. The speaker terminals were first connected to the PMC MB2se speakers, then Triangle’s excellent Borea BR09 floorstanders, this latter arrangement a much more likely real-world pairing since the BR09s come in at around £1,100 rather than the £26,000 of the PMCs.
Vinyl, CD or PC, it did not matter what source was chosen – the sonic results in each case were nothing less than properly satisfactory; the Triangles and the Cambridge transcribing recordings to a standard that when benchmarked against the four musical pillars was judged to achieve quality results quite out of proportion to the relatively modest cost of combined the boxes.
To keep things fair, I used the Tambaqui DAC only for an hour or so, before connecting the CD transport direct to the CXA61, thus using the amplifier’s internal DAC. As might be expected, there was a reduction in audio quality, but, in the grand scheme of things, not an especially huge one. Does that make the Tambaqui poor value? Nope. But it does illustrate the law of diminishing returns, and underscores what a fine job Cambridge has done with the CXA61, mitigating to a large extent the typically etched, bright and digital nature of the ESS delta-sigma DAC chip to give a sonic result that is somehow, whisper it, unexpectedly natural, approaching analogue.
With the CXA61 driving the Borea BR09s, on CD and via the S/PDIF input, I played White Winds, Andreas Vollenweider’s suite for concert harp; a well-recorded tone poem that makes the most of the richness and depth of the starring instrument, supported by an assorted cast of sound effects including percussive chimes, dripping oar blades and ethereal voices. On a high-end system it’s a properly immersive, almost full-body experience. Despite their low combined cost, the CXA61 and the BR09s still pulled me deeply into the sonic labyrinth created by Vollenweider, standing up the concert harp in the listening space with satisfying tonal density and dynamic weight, while the noises off were rendered with a level of transparency and detail that informed, but didn’t become distractingly intrusive.
From Qobuz and via the CXA61’s USB input, I played Apostolis Anthimos Live 29.01.2011, the Polish fusion guitarist with Cameroonian bass player Etienne M’Bappe and English drummer/pianist Gary Husband. The astute voicing of the CXA61, and its strong transparency, rendered M’Bappe’s bass with suitable dynamic bite and weight, and with generous tonal density. M’Bappe’s timing, right in the pocket with Husband’s percussion, was convincingly shown in counterpoint to Anthimos’s sometimes deliberately wayward shredding. Some much more costly amplifiers have made a hash of this material, but the CXA61 nailed it, delivering the driving rhythms with confidence and foot-tapping elan. It went loud too, only losing its composure when wound up to a frankly very un-neighbourly gain setting.
This review is going to come over to some readers as rather gushing, but I’d argue that context matters a lot. We might reasonably expect an amplifier costing four, five, six times as much to exhibit such a generous and balanced measure of the four key musical pillars, but the CXA61 does it for less than a grand.
No, 60 Watts per channel is not a lot, but the level of dynamic expression achieved by designer Stephen Tizzard provides strong compensation, meaning that the CXA61 doesn’t need to be played especially loud in order to create satisfying in-room pressure. With the CXA61 driving the 92.5dB Borea BR09s in my four by six metre listening room I was not left feeling short-changed. Agile, with expressive dynamics, tonally informative and with fine timing, the Cambridge Audio CXA61 is a genuine taste of high-end audio, without the high price-ticket.