Metrum Acoustics

High-End Non-Oversampling Converters

In the audio industry AE is primarily known today for its brand Metrum Acoustics. In the electrostatic speaker field their experience dates back to 1989 and gradually over time broader electronic applications have evolved.

A diverse range of acoustic system products have been created during this period, always relying on sound electronic design principles. Digital signal processing has played a significant role in more recent developments.

In hi-fidelity audio, AE's attention was initially drawn to the limited availability of certain components. Established manufacturers supplying these key components decide how signals should be processed. No alternatives are available and therefore this greatly influences the sound image that is realised.

Current trends among manufacturers are to use the technique of 'oversampling' or 'up-sampling' within the digital to analogue chipset itself. This forces designers to utilise this method of signal conversion for their own products. It also means that many brand systems use the same building blocks and consequently sound the same. The sound images created by such systems can actually betray the component that has been implemented.

These sampling techniques were introduced to fulfil the need 'to smooth' the conversion process from digital to analogue and prevent phase distortion. Particularly during the years following the introduction of CD replay, conversion methods proved insufficient with regard to sonic artefacts. In response strong filtering methods were employed and the oversampling technique was born. These techniques however have disadvantages which manifest themselves for example in areas of transient response.

Today there is a growing view that 'non oversampling' or NOS for short, offers many benefits but without the compromises mentioned above. AE dedicated considerable time and attention to researching the NOS premise and found its audible benefits valid up to a certain point.

The question then remained how to remove these sonic artefacts without resorting to oversampling. This question was answered by the first product made by AE: the NOS mini DAC Quad, a digital to analogue converter designed and manufactured with modern high speed industrial grade chipsets, free from most of the disadvantages of the past. These techniques are improved over time and used over the entire range of products. The most important result is the sound, which was never so close to the analogue origin.