Tuner group test - Cambridge Audio 640T

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Tuner group test
NAD C422
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Cambridge Audio 640T
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The first of the three hybrid DAB/FM designs, the Cambridge sports the best silver coating of the group, with finely countersunk openings for the centrally located display and buttons either side. The poorly legible LC display is a disappointment. To its right are countersunk buttons for DAB/FM, Autotune, Info, Select and Left and Right Arrow symbols for tuning. The side panels are attractive extruded aluminium C-sections, each smoothly folded six times. The top plate is nicely screwed into the main chassis with flush mounted countersunk star head fixings.


Inside the Cambridge also features a Radioscape DSP similar to the Arcam, which takes both the FM (with direct digital synthesis and digital demodulation) and DAB through the digital DSP. The DAB module uses a Texas Instruments fixed point DRE200 chip while the DAC is a Wolfson WM8716 24/192Khz type with 48kHz sample rate. A frame transformer feeds a linear power supply. At the rear panel, there is an F-Type aerial socket for DAB/FM, gold-plated electrical digital out, optical digital out, input loop through phono sockets to save an input socket on an amplifier, output phono sockets, switchable ‘Natural Contour Technology. Vital statistics are 70x430x305mm and 3.9kg.


The Cambridge produced one of the best results for the group on both FM and DAB. On Radio Two DAB 128kbps, it featured a vibrant sound that I thought was not possible on DAB, let alone the lower bitrate of 128Kbps! It proved thoroughly enjoyable, with the vocals in music being beautifully presented. On Radio Three DAB 192kbps, orchestration was lush and unrestrained - where the Cambridge handled the crashing crescendos without strain. I couldn’t discern any DAB compression or sibilance to the vocals either.


With Radio Two FM, the sound gained in spatiality in comparison to the Cambridge’s own DAB version.. Radio Three FM also had an excellent showing; violins were really tangible while horns were well rounded and dynamically resolved, convincingly, naturally, rendered. Still, the Cambridge did have discernible midrange smear on both DAB and FM compared to the other tuners, but this did not detract from an otherwise brilliant performance.


An excellent all rounder and an absolute pleasure to use and listen to, this tuner is very well built, finished, priced and designed - few hi-fi components tick all four of these boxes! In absolute terms it can’t quite match the Creek, NAD or the reference on FM, but remains absolutely outstanding value for money.


The Cambridge Audio Azur 640T is very similar to Arcam’s DT-91, using a Radioscape DAB/VHF module, but there are differences. Cambridge have fitted switchable frequency response equalisation to the rear panel, marked "warm" and "lively" in addition to normal (flat). Warm lifts bass only, by around +3dB below 450Hz – quite a lot. Lively lifts bass less, by +3dB again but below 250Hz. It also raises treble level to add  some brightness. Switched to Flat the 640T gave a smooth response with slightly rolled off upper treble, our analysis shows. Like the Arcam, pilot tone at 19kHz barely existed, measuring –90dB. There was little intermod. against this tone as a result. Distortion levels were lower than those from the Arcam too, quite significantly so in the midband on stereo signals (L+R and L-R) at 0.05%, if not on full left and right signals (L, R) at 0.2%.


The 640T also turned in 3dB less noise, managing –66dB (IEC A wtd.), so it appears to have a better spec. Radioscape module inside, but hiss will still be audible at times, minimised only by the compression and lack of silences on most radio programme.


Like Arcam’s DT-91 the 640T was massively sensitive, maintaining minimum hiss (full quieting) down to a miniscule 22uV. For this alone, to most people, who have poor aerials, it may well seem unusually quiet. It neither needs nor benefits from a big outdoor aerial. Another mixed bag, but interesting. NK



Frequency response  10Hz-10.6kHz

Stereo separation 60dB

Distortion (50% mod.) 0.2%

Hiss (CCIR) -66dB

Signal for minimum hiss (50ohms) 22uV

Output 0.78V

Sensitivity (50ohms)

mono  1.4µV

stereo 12µV

signal strength meter: reads up to 9uV




verdict 5

Cambridge Audio

+44 (0)207 940 2200



- blistering value

- superb design, build

- excellent sound quality



- poor display

- no rotary knob



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