Music in the Round #27
In the years since, we've seen the coming of other multichannel analog preamps—and the going of some of the most aggressively priced ones, such as the Sony and the Audio Refinement Pre5 ($995). This makes some sense. Multichannel sources are digital; the only buyers likely to insist on an analog multichannel preamp are high-enders concerned with maintaining the purity of their analog sources. Hey, I've been in that camp from the get-go.
But the ground is changing under our feet. Nowadays we must accommodate multiple and evolving digital inputs. How to deal with those digital sources while keeping our analog sources pristine? The common approach is to relegate all digital decoding and processing to the source devices, then feed them to an analog preamp—which leaves the signal subject to the limited processing included in most source devices. Another way is to build an analog preamplifier into a digital preamplifier-processor, as Bryston does in their SP-2 that I wrote about in September 2006. Now there's a third way.
Atoll Electronique PR5.1 multichannel preamplifier
Musical Sounds is the US distributor of a number of interesting European manufacturers, including Atoll Electronique. Atoll's IN100 integrated amplifier ($1500) so impressed Sam Tellig when he reviewed it in April 2003 (Vol.26 No.4) that he nominated it for Budget Product of the Year. Buried among Atoll's wide array of two-channel products is the PR5.1 ($2500), a pure analog preamplifier with two six-channel and four stereo inputs. Like all Atoll Electronique products, the PR5.1 is made in France, mostly by hand, and is styled with simple grace.
Although the PR5.1 is superficially like the Sony TA-P9000ES, all of its inputs are controlled by its volume and balance controls, and there's even an option to convert one input to a phono stage. Unlike the McCormack MAP-1, the Atoll has no surround synthesis mode, and unlike the McIntosh C45, it has no tone controls. In fact, the Atoll is, operationally, most akin to my reference Bel Canto Pre6 (reviewed in December 2003) and the recently reviewed Audio Research MP1 (September 2007), at a much lower price.
All that would be sufficient justification for our interest, but the Atoll has one feature that distinguishes it from all other models: For an extra $375, Atoll will graft onto the PR5.1 what it calls "the DSP Option." This adds three digital inputs and one digital output (all as optical and coax), three video inputs and one video output (all as composite and S-video), and some swift software that integrates all the new functions without disturbing the classic operations of the basic analog preamplifier. The D/A section is specified as using Burr-Brown "24-bit/96kHz" converters. Amazingly, the main analog PCB remains completely unchanged; the two circuit boards comprising the DSP Option are mounted on existing headers. Of necessity, additional holes are added to the rear panel.
You can see the segregation of the basic analog preamp from the DSP add-on by just looking at the rear panel. All analog ins and outs are organized in two tidy rows along the lower half of the panel, all digital and video ins/outs in the upper half. In fact, from the front panel, the only hint of the DSP Option's presence is a single LED indicating the selection of a source numerique (digital). The PR5.1 accepts and decodes Dolby Digital, DTS, MPEG (2.0 to 5.1 channel), and, of course, S/PDIF. It's still an analog preamp—not a digital preamp with an analog bypass. Or perhaps it's more accurate to call it an analog preamp with a built-in A/V pre-pro.
The PR5.1's front panel displays the volume level and the source (by name). This display is also used in setup, as there's no video output for any sort of onscreen display—not with the DSP Option, and certainly not without it. Below the display are seven buttons: Display (on/off), Mode (surround/stereo), Config (accesses setup menus), Mute (on/off), A/V (switches between the original analog input banks and those added with the DSP Option), Num (switches between the digital or analog source for a given input), and Standby. To the right of the display are up-and-down pairs of Vol (volume) and Sel (select) buttons to step through those choices. Obviously, some of these choices are of no significance without the DSP Option; surprisingly, Config is not one of them. Even in the pure analog-preamp edition of the PR5.1, Config lets you control the relative levels of all six channels. Add the DSP Option and you gain the ability to control channel delay (calibrated in meters), speaker size (for bass management), and dynamic range control (DRC), which I disdain. The bass-management crossover is a single selection for speakers designated Small and the options are 40, 60, 80, 100, and 120Hz. The clean, compact remote control gives access to all of the functions listed above, as well as very useful direct access to sources.
Despite the cursory nature of Atoll's owner's manual, installing the PR5.1 in my weekend system was about the easiest multichannel preamp swap I've done. While the manual describes every input and lists every option in the Configuration menus, it offers only one connection diagram, the figures are small and of limited resolution, and some of the English seems stiffly translated from the French. Anyone who's installed a pre-pro should have no trouble, but beginners might need a little help. I did like the use of shading to highlight the functions added with the DSP Option and clearly distinguish them from the basic analog operations.
I connected my Denon DV-3910 universal player and Pioneer Elite BDP-HD1 Blu-ray player to the PR5.1 by both six analog and by coaxial S/PDIF cables. (I didn't use any of the PR5.1's video inputs—in these days of component, DVI, and HDMI, its limited composite and S-video options are almost quaint.) I set the front three channels to Large and the rear channels to Small, crossing over to the subwoofer at 60Hz, both in the players (for their analog audio outputs) and in the Atoll (for its digital audio inputs). The PR5.1 applies its channel-level settings to all sources, analog or digital, in its analog circuits, which meant that I had to delete such settings in the Denon. Of course, since the PR5.1's channel delay and bass management are applied only to its digital inputs, this left the Blu-ray player the only source deprived of proper distance/delay, which were marginally audible in direct comparisons with the Denon.
Otherwise, everything worked as one would like: The operation of the PR5.1 was faultless, with no switching transients, noises, or dropouts. It seemed to lock on to and decode a digital input as swiftly as it did analog inputs. Using the PR5.1, new converts to surround sound will have no difficulty making the transition from two-channel.
The sound, too, was excellent, with good center fill and surprisingly good spectral balance from plain old S/PDIF data from CDs or cable music channels. In fact, as with the Cary Cinema 11 that preceded the PR5.1, I never found it necessary or desirable to impose signal processing, such as Dolby Pro Logic II, on two-channel sources, which already sounded full and spacious. Comparisons of the S/PDIF inputs with their companion analog sources—in other words, comparisons of the DACs in the sources with the DACs in the PR5.1—yielded varying outcomes. The stereo analog feed from the cable box was flatter in depth and less dynamic-sounding than the S/PDIF feed decoded by the PR5.1.
However, I wasn't so sure about my relative preference for the Denon DV-3910 when playing CDs, or DD or DTS music discs. Diego Amador's Piano Jondo (CD, World Village 468071) is a deft amalgam of flamenco and jazz in which Amador's piano replaces the usual guitar. In addition to presenting the accompanying bass, percussion, dance, and palmas with detail and punctuation, the PR5.1 delivered the piano (and the occasional guitar) with warmth and richness. Piano Jondo didn't sound much better than through the Denon's analog outputs, but the PR5.1's Burr-Brown DACs were clearly capable of swimming with the audiophile sharks.
With good discrete multichannel sources—eg, Hánssler Classic's recent releases of Schoenberg's Gurrelieder (see sidebar, "Recordings in the Round") or the Berlioz Requiem (SACD 93.131)—the PR5.1 acquitted itself handsomely, providing a broad, deep soundstage well integrated with the surrounding ambience. The frequency balance was on the light side, but with decent, full bass as required. The PR5.1 performed as well at high volume levels as at normal ones, but seemed to thin out a bit at low levels. I could have patched that up by invoking the dynamic range control, but for the purposes of this review I preferred to tweak the system by running all speakers as Small and bumping the subwoofer level up by 3dB. Fortunately, I seldom have to listen at low levels. At just normal levels, I could hear both the attacks and the decays as they propagate through the large studio room on the wonderfully atmospheric Sinestre: Late Piano Works: the young Péter Tóth playing Liszt (SACD, Stockfisch SFR 357.4040.2).