Audio Research DS450 review

Given its penchant for producing large, heavy, behemoths, Audio Research's launching of a Class D power amp, the new DS450, is more than slightly surprising.

While Pure Class A still sets a benchmark when the highest quality results take precedence, there are many practical drawbacks – excessive heat, large size, high price, massive power consumption – need one go on?

The DS450, on the other hand, features an analogue-based Class D pulse-width modulated switching output stage. High output power, low-running temperature, low power consumption and excellent sound quality are promised. But can such clever technology really challenge Class A's sonic supremacy?

Up the stakes

Like most power amps, the DS450 is fairly simple. You've a choice of unbalanced/balanced inputs – via RCA/XLR sockets – and a single set of loudspeaker output terminals using Cardas binding posts. Add a mains on/off switch, plus sockets for remote on/off and that's about it.

Audio Research first used pulsewidth modulation technology in its DSi200 integrated. But the DS450, ups the stakes, employing twice as many 500-watt MOSFET power devices on each side. As a result, the DS450 delivers around 450W per channel into eight ohms.

A conventional Class A/B amplifier offering this sort of output would run fairly warm. But the Class D DS450, being around 93 per cent efficient, produces hardly any heat. So, you could hide the amplifier away in a cupboard without having to worry about ventilation.

Audio Research's website mentions this and even suggests users might want to leave the amp permanently switched-on for best sound quality. However, the DS450 sounds good from 'cold' and is pretty close to optimum after about 25-30 minutes, so there's not much need. Idle, the DS450 only consumes 55 watts.

Many previous ARC power amps have been massively big and heavy, producing huge quantities of heat, while drawing sizeable amounts of current from the mains supply. Indeed, the company's reputation was built on no-compromise designs that sacrificed everything for sound quality. So the eco-friendly DS450 is a totally new departure.

It's not just that it's solid-state, rather than tube; Class D pulse-width modulation technology is the real talking point. Given the reputation of ARC's Class A tube designs, the DS450 has a lot to live up to. While no one's claiming Class D amplifiers are sonically superior to their pure Class A counterparts, the practical and environmental advantages of the former are not to be under-valued. So, listen without prejudice – the DS450 sounds extremely good.

The best sound is produced via the balanced inputs. To utilise these you'll need a preamp with balanced outputs. Audio Research's LS26 offers this option. With balanced you can look forward to a more spacious sound, with increased dynamics. So, investing in a set of XLR balanced cables is mandatory.

Physically, the DS450 is almost totally silent – no transformer buzz, and (obviously) no noise from cooling fans. The amp is quiet electrically, so those with ultra-efficient speakers should hear no residual hiss or hum – even with an ear to the drive units!

Traditional image

In terms of styling, the DS450 is traditional Audio Research, complete with signature grab handles on the front. While the DS450 is not massively heavy, it is fairly big and ungainly, so the handles are useful. The amp is quite solidly made, but we're not talking heavy 'battleship build' here.

The casework is made from brushed aluminium, with a front panel just under one millimetre thick. Being non-magnetic, aluminium should deliver a sweeter, more open sound compared to a steel case, due to reduced eddy current effects.

Meanwhile, the lightweight chassis should also reduce the adverse effects of air and structure-borne vibration. Finish is extremely good and the sculpted Audio Research logo looks cool and classy.

The internal layout is extremely neat and the Cardas speaker binding posts are easy to use and give clean and tight connections. ARC has given the amp a generous power supply with a large power transformer and something like 1239 Joules of energy storage – twice that of the DSi200!

Hence the DS450 weighs in around 25kg (55lbs)and is somewhat front-heavy, because the power transformer is forwardly placed.

Manufactured, built, and tested in ARC's Plymouth Minnesota factory – the DS450 is not assembled from parts fabricated elsewhere, or built in the Far East. Many components are custom-made and/or designed in-house, including power transformers, filter chokes and the Litz wiring used internally.

Lucid sound

The DS450 replaced a Musical Fidelity kW-750 power amp driving Impulse H1 loudspeakers. Our preamp was a Musical Fidelity Primo (pure Class A tube) with a Musical Fidelity AMS tube CD player. The kW-750 is a powerful (750 watts) Class A/B bridged design with unbalanced inputs.