The Azur 840A is the most flexible, most powerful, and best-sounding integrated amplifier that the British firm Cambridge Audio has ever built, and it even introduces a new “Class XD” mode of amplifier operation that I discuss in the sidebar, below. Briefly, Cambridge’s Class XD circuit leverages the strengths of Class A and B amplification in an innovative way, yielding lower distortion than is typically produced by traditional Class AB amplifiers. Interestingly, the 840A is also a “multizone” integrated amplifier, in that it provides dual ABUS interfaces that can send audio signals via CAT5 wiring to two remote listening zones. The 840A puts out a feisty 120Wpc, and sells for $1499.
The Azur 840A incorporates numerous touches that purist audiophiles will appreciate. For example, the amplifier provides separate power supplies for its preamplifier and power amplifier sections, and offers eight usernameable analog inputs—including one that supports both single-ended and balanced input jacks. Any of the amplifier’s inputs can be locked to fixed gain levels, making the Cambridge ideal for home-theater passthrough applications. Switch-selectable balance and tone controls are provided, as is a front-panel “Direct” control that ensures the cleanest signal path possible. Finally, to complement its low-distortion circuitry, the 840A controls output levels via a relay-controlled precision-matched resistor ladder.
Over time, I’ve heard a number of small British integrated amplifiers that to some degree fit the stereotype of sounding warm, softly focused, and polite. The 840A is not among them. Right out of the box, the 840A exhibited a big bold sound characterized by terrific midrange definition and detail, and by clean powerful bass. By comparison, the mid-priced YBA Designs YA201 amplifier I reviewed in Issue 165 was more of a contemplative sonic introvert, where Cambridge Audio Azur 840A Class XD Integrated Amplifier Playing above the grade the ebullient Cambridge puts its lively and engaging sound right out in the open for all to hear. In short, the moderately priced 840A signals from the outset that it wants to play with the big boys. And in many ways it can.
One important way in which the 840A seems to play above its pay grade is in carving the leading edges of transients with the sort of energy and definition I normally associate with more expensive amplifiers. A multifaceted musical example will help to illustrate this point. I put on Long John Hunter’s “Let’s Set The Time” from the Untapped Blues Festival 2004 Live album [Bluestopia], and I came away marveling at how vividly alive the 840A made Hunter and his band sound. If you enjoy listening to (or playing) electric guitar at moderate volume levels, then you already know how sound seems to erupt from the guitar amplifier a split second after the pick sweeps past the guitar strings. In fact, some notes can launch so hard that you might initially expect the sound to become unpleasantly loud. But when recording and playback levels are set just so, what actually happens is that individual notes cry out with gripping visceral authority, yet without ever reaching painful levels. This punchy evocative sound is exactly what the 840A achieved in reproducing Hunter’s guitar solos on “Let’s Set The Time.”
Similarly, the 840A did a spectacular job with the sound of keyboardist Tommy Washington’s electric organ. If you listen closely, you’ll observe that some electric organs (typically older Hammonds) produce a soft slightly scratchy-sounding “click” just as their keys are depressed. These clicks might actually be indicative of wear in the instrument, but many experienced blues keyboardists— Washington among them—use those key clicks to give the notes in fast-paced runs a bit more kick and definition. The Cambridge amp nailed the powerful sound of the organ, clicks and all, and it perfectly caught the eerie shimmer of the Leslie rotary speaker used to give the organ its voice (Leslie speakers feature a rotating horn tweeter whose sweep speed can be controlled by a foot pedal).
Finally, the Cambridge did a gutsy job with the sound of bassist Tracy Mortimer’s electric bass, which sounds clean, clear, and absolutely thunderous on the Untapped Blues Festival disc. Even though four-string basses don’t reach down into true low-bass territory they are still difficult to reproduce, partly because they have deceptively complex timbres, and partly because they impose abrupt large-scale power demands on amplifiers. The trick is that amplifiers must answer those demands without losing composure or detail in the midrange and treble regions. Even when I cranked up “Let’s Set The Time” to quite invigorating volume levels, the Cambridge took Mortimer’s propulsive bass lines in stride while keeping the rest of the band in sharp focus.