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Sony has a long history of radio design. It built Japan's first transistor radio back in August 1955. Then, two years later, it launched the smallest radio in the world at the time, the TR-63. This was a truly pocketable device, setting the standard for tuners for the rest of the century.
We were disappointed with Sony's kitchen DAB, the XDR-S20, but its foray into the hi-fi separates market looks considerably more faithful to the high ideals of its engineers back in the 50s. At first glance the ST-SDB900 is a solid unit with both analogue and digital audio outputs to interconnect your existing stereo system.
As with all DAB separates, you'll need an existing amplifier and speaker set to plug the unit into. Unlike the PURE DRX-702ES, this Sony radio does not have a built-in headphone jack, so listening without an amplifier is not possible.
Though DAB stations in the UK still use disappointingly low bit rates (sometimes slumping into the gutter of 80Kbps), for audiophiles there is always the option of listening to FM broadcasts on the ST-SDB900 where they're available. Of course, the overwhelming reason to listen to DAB is the sheer choice of stations, so how does this Sony compare to the competition when it comes to decoding and playing DAB broadcasts?
The clean and uncomplicated fascia on the ST-SDB900 is typical of higher-end Sony separates systems. Controls are clearly displayed, with a large tuning dial dominating the right hand side of the unit. This rapidly scrolls through stations like a traditional tuner.
Either side of the large (16x2 characters), bright LCD display are six function buttons, which let you summon menus, change band and recall memory presets. They're simple buttons not much bigger than a pinhead, and they let you operate the unit even when you've mislaid the remote control.
Sony has made one design error in this otherwise flawless chassis, and that's to run screws through the top of the casing, marring the smooth top of the system. For this reason, you probably won't want to use this DAB as the top unit in a free-standing hi-fi stack -- it doesn't quite have the style to pull it off. It's a small niggle, but it could have easily been avoided.
The ST-SDB900 uses a standard 19-inch case that stacks neatly on your existing hi-fi separates. The feet on the unit raise it about a centimetre off the ground, providing adequate ventilation for an amplifier placed below.
The rear panel on the Sony offers a sparse but well-chosen array of outputs, in the form of digital optical and gold-plated phono connectors. The ST-SDB900 doesn't have the wealth of inputs and outputs that the PURE DRX-702ES sports, but because the Sony has digital optical outs, you've got everything you should need. Anything beyond this is really only useful for extremely specialist applications at the moment.
The ST-SDB900 autotunes rapidly -- it's on a par with other separates we've tested. Radio stations are automatically listed, and you can scroll through stations using the tuning wheel. Initial setup is easy and won't tax anyone who's familiar with using a kitchen DAB, or a long-term radio user.
Hooking up the ST-SDB900 to your current stereo system can be done using the digital optical outs or the phono outs. Most listeners will find that their amplifier supports only the traditional phono connectors, in which case, a good pair of phono interconnects (a very basic set is included) will do the job of connecting the Sony to an amp.
Higher-end modern amplifiers may have an optical input, in which case you can run an optical cable (not included) from the DAB to your amplifier. Given the low bit rate of DAB, you're unlikely to hear a massive improvement over the phono interconnects, but you will eliminate potential problems with ground loops etc.
Every UK DAB broadcast is compatible with the ST-SDB900 -- all Band III transmissions can be received on the tuner at up to 256Kbps. If you're not convinced by DAB, or are having reception problems, FM frequencies available to the Sony range from 87.5 to 108MHz. Again, this encompasses all commercial FM broadcasts in the UK.
FM, AM and DAB bands can be tuned using the dial on the right of the unit, and the unit includes a range of view options, including the ability to sort stations alphabetically.
Sony claims to have used independent power supplies to isolate the audio and DAB circuits from the other circuits in the ST-SDB900. This was difficult to verify, but a cursory examination of the inside of the radio made it possible to identify what appear to be different power stages. This should make for a cleaner sound -- more on that later.
Efforts have been made to dampen the circuits and the chassis, and vibration is minimised by polycarbonate on the rear panel, teflon on the side panels and a 'bonded material' on the front panel. Though hi-fi isolation is dismissed as an old wives' tale by cynics, many audiophiles swear by the minimalisation of vibration in their separates. Some go so far as to place bricks on carefully chosen pieces of equipment. Given this behaviour, there may well be something to the ST-SDB900's floating construction.
Power is supplied via a sturdy kettle-lead style connector. AM, FM and DAB aerials attach to the rear of the unit -- Sony includes all three types of aerial and these are easily attached.
Auditioning the ST-SDB900 with a Radio 4 DAB broadcast illuminated the unit's strengths in producing an accurate and well-balanced sound on our reference amplifier and speaker set. Though DAB is still at the mercy of radio engineers who love to compress -- not to mention the low bit rate of UK DAB broadcasts -- the ST-SDB900 compares very well to other tuners in its class.
Listening to Radio One was, again, comparatively good. Within the limits of the broadcast, the sound quality was rounded, not too bright and not excessively bassy. The broadcast was, however, noticeably muddy with compression -- something that's problematic for all separate tuners. The sad fact is that the DAB signal just doesn't stand up when heard on a good stereo system and for music, in particular, is a disappointment. Spoken-word broadcasts, however, are exceptionally clear.
There's very little to divide the hi-fi DABs we've looked at so far. They're all like very talented artists being made to paint with crayons. The DAB bit rate can't tax these tuners.
For appearance, this Sony DAB may not have the edge, but for simplicity of set-up it's hard to beat. The ST-SDB900 is definitely worth considering if you want to bring DAB into an existing hi-fi setup, and for owners of a Sony amplifier this tuner is definitely the most logical choice for expansion.
Edited by Mary Lojkine
Additional editing by Nick Hide