Digital amplifiers have been hailed as the next big thing in audio amplifier design.
Of course, this claim has been made for at least the last 15 years, during which time the technology has consistently failed to attract audiophile interest. But increasingly they have found a niche in compact, all-in-one systems, where they deliver both slimline aesthetics and a financial edge.
Newer implementations have hinted that there is more to digital amplification than modern music centres - Sony's go-for-broke TA-DA9000ES being perhaps the most ambitious of its ilk to date - but we've waited some time to see a demonstrable quality jump. Could the SA-XR55 be the missing digital link?
Panasonic has been making digital home cinema receivers for a considerable period, mostly low-cost and relatively low-spec. The SA-XR55 reviewed here, though, breaks that mould. While still qualifying for budget status - it typically sells for around £260 - it is surprisingly well specified.
The amplifier is a 7.1 channel design, which is rated by Panasonic at 100W/channel DIN 1kHz into 6ohms, which in real money corresponds to 90W into 8ohms in stereo mode, dropping only to 85W with five channels driven (results courtesy of our independent Tech Labs).
Some of this grunt comes via a dualamp drive system which doubles up the amplifier current drive when listening in stereo; this is achieved without resorting to biwiring the speakers, and is selected automatically with two-channel sources. The front speakers can also be biamplified (that is, powering the bass drivers and the tweeters with separate power amplifiers when the speaker is biwired), adding even more brawn to the sound.
Build quality is good. I was pleased to note that all seven speaker channels are served by 4mm binding posts, where previous Panasonic models have been stuck with cheapo spring terminals for some of the channels. In some ways the design isn't as forward-thinking as I might have liked. A nice refinement would have been a 'display off' feature with audio direct in order to defeat the video circuitry when listening to audio only discs.
Sky and plasma users might also have appreciated an adjustable audio delay feature, but this would have required extra internal memory and therefore increased the cost. In fact, there are remarkably few toys of the kind that make most AV amps and receivers so endlessly confusing, but you do get a 30 preset FM-RDS/MW tuner.
Naturally, the SA-XR55 is equipped with all the expected surround sound codecs and the maker claims that the amplifier is DVD-Audio ready by virtue of a 88kHz power bandwidth. This claim should be taken with a pinch of salt.
The frequency response of DVD-Audio extends to 88kHz only for stereo recordings, but in practice you'll find it hard to find recordings that are not multichannel, and therefore limited to 44kHz at the top end.
More to the point, there are questions about this Panasonic's high frequency performance. The response shape is not exactly linear even within the 20kHz-ish limits associated with compact disc and DVD-Video, and the signal/noise performance is on a steep decline towards the top of the so-called audio frequency band.
Included with the package is a well designed (and well packed) remote control whose internal codes and external controls can be used to operate most TVs, VCRs and DVD players/recorders, even from other brands. The rear panel is sensibly laid out and easy to get to grips with, and the simple front panel controls make day-to-day operation a breeze.
There is no way of avoiding this: previous generations of Panasonic digital amplifiers have been disappointing. They were ultra affordable, though, which reduced the pain. This one is clearly cut from a different cloth.
It has an immediacy and clarity which is quite out of the norm for the price point. The SA-XR55's sound remains remarkably clean and tactile, provided the volume levels are kept in check. In many ways, sound quality improves the lower the volume is set. Crank it up and you'll discover a rather brash, edgy tonality. This is not an amplifier that relishes being driven hard.
Within normal tolerances, though, I found it dynamic and exciting. Multichannel film scores, like that on Finding Nemo, enjoy strong resolution and fine detail. The Panasonic had no problems with the subtle and complex surround effects on this recording.
The receiver was generally at its best with soundtracks that don't depend for their effect on the kind of overall statement that is necessary, for example, in Kill Bill, which in climatic moments with the volume control set to 'stun' tended to sound a bit synthetic. But for general TV and movie duties, it was always entertaining.
Summarising the SA-XR55 is not entirely straightforward. It has an ungimmicky set of user features and enough power to give it traction, albeit subject to the caveats already noted.
The digital internal architecture of the amplifier has genuine clarity and punch. It also earns bonus points for sheer value for money. I wouldn't advocate it if you're looking for a two-channel musical solution; however, if you're looking for a receiver to partner a flatscreen, in a relatively small cubic area (ie most UK apartments), it makes a surprisingly good choice.
Overall, this is probably the most convincing, affordable digital home cinema amplifier we've seen to date.