Arcam Delta 120.2
Power Amplifier

Arcam Delta 110 Digital Preamplifier and Delta 120 Power Amplifier

ARCAM DELTA 110 DIGITAL PREAMPLIFIER AND DELTA 120 POWER AMPLIFIER future most of our audio processing may well be digital rather than analogue. Processors will be so compact, inexpensive and reliable that digital converters will become the norm, both as stand-alone units and built into amplifiers, receivers, etc., extending all the way from the ultimate in hi-fi down to the cheap and cheerful.

At present, however, digital processors remain relatively expensive and their sonic benefits are widely regarded as being of a magnitude that only golden-eared audiophiles might appreciate. It follows, therefore, that anyone designing a digital amplifier would do well to target the fussy audiophile community and build into the design as many other refinements as possible. The A&R Cambridge (Arcam) team are well aware of this, and have taken a lead already with their stand-alone Black Box D/A converters and CD transports (see my review of the Black Box 2 and Delta 170 in September 1989). The latest Delta 110 digital preamplifier (019.90) and Delta 120 stereo power amplifier (£519.90) reviewed here both incorporate special features aimed at helping the pernickety enthusiast to optimize the reproduced sound quality-though operational comforts have not been forgotten, as witness the provision of a cordless remote control handset.

The Delta 120 Power Amplifier

The casing and front panel of the Delta 120 power amplifier are neatly styled to match the Delta 110. However, the front panel is almost devoid of controls, carrying only a pair of on/off buttons for Speakers A and B, which operate heavy-duty relays close to the speaker terminals, and Power on/off with a green indicator LED. The rear panel is suitably busy, though, providing a range of possible operating modes. The two pairs of loudspeaker terminals will accept any type of bare wire or 4mm plug connector and are located at the centre between the two sets of heatsink cooling vanes. The IEC mains connector is at one end of the panel, with audio inputs and mode switches at the other. There are two pairs of input phono sockets labelled "Direct" and "AC Coupled". The former has a bass response extending to below 1Hz and just might provide better sound quality with some wide-ranging source material and appropriate loudspeakers. DC protection relay circuits are built-in to disconnect the loudspeakers in the event of an excessive DC offset. The alternative "AC Coupled" input might be a more satisfactory, and safer, option since it incorporates a series capacitor to limit the subsonic response, falling to -3dB at approximately 3Hz.

Two mode switches are fitted which provide, respectively, mono (paralleled input) operation and bridged mono. This is all made possible by the fact that in reality the Delta 120 consists of two totally separate 100W mono amplifiers with their own toroidal mains transformers and power supply circuits. Four modes of operation can be set up:

(A) Normal stereo
you simply connect Left and Right speakers to the Speakers A or B terminals, or to both provided the combined impedance does not fall below 4 Ohms.
(B) Bi-wired stereo
you connect the two pairs of Speakers A terminals to the treble terminals of your loudspeakers and run a separate pair of cables from Speakers B to the bass terminals. If you like the bi-wired results, you can then of course attach both sets of cables to the Speakers A terminals. This will leave the Speakers B terminals free for a second pair of loudspeakers.
(C) Bi-amplified stereo
you need two Delta 120 amplifiers with their mono buttons pressed. One amplifier takes the Left source channel bi-wired via its Left and Right terminals to the Left loudspeaker and the other takes the Right.
(D) Bridged mono
this drives the two channels of a Delta 120 in antiphase, by introducing an inverting amplifier at the input to one channel, to provide a powerful (300W) mono output across the two red (positive) L/ R terminals. Again two Delta 120s will be needed for stereo and bi-wiring is possible-though note that you will need to choose suitably powercapable loudspeakers. The instructions booklet makes all this very clear.

How they performed

I think I have said enough to confirm that this Arcam amplifier combination makes it easy for tweak addicts to experiment with most of the common audiophile variables: analogue versus digital CD player outlets, optical digital link versus electrical, absolute phase reversal, bi-wiring and hi-amplification: and, by the way, the special AudioQuest connector cables supplied are "directional" so that you can also try the effect of reversing them end-to-end--though I note that the manufacturers state that,

Internal view of the Delta 120 power amplifier "Depending on the equipment there might be no difference, a little difference or a major difference. Once you know the preferred direction for your equipment, that will be the better sounding direction for your equipment for all twin-axial cable." This sounds a bit like sitting on the fence to me, and mirrors my own conclusions exactly.

I have always been fairly sceptical of this sort of claim, particularly in some of the worst examples where pseudo-scientific language is used and dramatic improvements are promised. Too often I have found any detectable differences to be bordering on the insignificant and quite outweighed by the added expense and complexity. However, I have considerable respect for Arcam products and, I was presented here with an opportunity to try out various comparisons in the course of this review. Keeping an open mind, as always, I did indeed spend some

On most musical material, but not all, the AudioQuest interconnects did outperform a pair of 'cooking sherry' phono leads, and I almost persuaded myself that I preferred them connected in the recommended direction. However, the many crossings-out on my mark sheet, and the contradictory results turned in by other listeners, indicate that any differences are slight and have to do with such imponderables as centre image definition and the apparent ambience or 'air' around the instruments and voices. It was the same when comparing CD player analogue and digital outlets, absolute phase reversal and bi-wiring: slight differences could be detected most of the time but would they show up equally with other loudspeakers in other circumstances? My advice can only be to try it out for yourself-your Arcam dealer will be happy to demonstrate-and, as the AudioQuest notes state, "Use the direction that sounds better".

I am on much firmer ground with the main purpose of this review: this Delta 1101120 combination easily met its technical specification and it showed itself capable of remarkable sound quality on all inputs. Wide dynamics came over with a special feeling of impact and fidelity to the live music experience. There was a remarkable degree of transparency and depth through the built-in D/A converters, using the digital outlet on any decent CD player, which suggests to me that they are amongst the best converters you will find anywhere. The Bitstream technology has been described by some critics as strong on natural warmth but weak on excitement. On this showing, the Arcam designers have taken the Bitstream system and `breathed' on it in such a way as to surpass the general run of multi-bit converters-and even the best analogue systems. Recordings on CD and LP which I have played so often that I feel I know them intimately took on a new clarity and luminous presence.

This amplifier combination cannot fail to attract a lot of favourable attention. It is versatile and lends itself to later upgrading, e.g. to bi-amplification, and would probably see off competing high-end amplifier systems costing twice as much.

Incidentally I have just learned that a Delta 110S analogue version of the preamplifier is to be marketed. The D/A converter board is omitted, and a sixth line level analogue input substituted for the coaxial digital sockets. The Delta 110S will cost £519.90, instead of £719.90 for the 110, but it can be modified at a later date by adding the D/A board for around £250.