Materials Technology   On this Page :   Acrylic?    Fields    End Result   We at DNM find the phrase "built like a tank" bemusing, especially when applied to hi-fi and not to armoured vehicles! Despite producing products which handle delicate audio signals, many companies justify high prices with earthquake-proof designs which would put Isambard Kingdom Brunel to shame! While all good hi-fi needs to be built to last, we believe that such engineering overkill serves only to hamper the delicate musical signal. Magnetic Fields Any piece of hi-fi has to process complex audio signals, which are made up of fast-moving mixtures of level, frequency and dynamic range. These signals when passing along a wire, a circuit track or through a component have electrical properties, creating magnetic fields in their wake. These magnetic fields generate new fields by interacting with unnecessary metallic items in the audio chain or even in the casework, resulting in interference. Sonically this translates into dynamic compression and a 'dirty' sound, making listening to detailed information all but impossible. Non-Magnetic? Some metals are believed to be 'non-magnetic'. Alloys of aluminium and magnesium are often used for casework in place of steel for this reason.

This statement is based on the behaviour of the metal when exposed to a simple constant magnet, i.e. field. However, under alternating current (AC) conditions (e.g. the intricate workings of a hi-fi amplifier), these alloys prove to be extremely magnetic, creating eddy currents which interfere with the all-important audio signal. Acrylic Cases     We have deliberately built our amplifiers into cases of high-quality acrylic as it is a non-conductive material with no magnetic properties. It looks good, too! Closer inspection of any current DNM design will show that the use of any type of metal in proximity to the electrical signal path has been virtually eliminated. Minimal Metal The input and output connections of all DNM units use custom-made plastic bodied DIN sockets. The DIN connection, although not widely used in domestic audio, has the significant advantage of lower metal content compared to its RCA equivalent. In addition, the DIN connectors used by DNM are a bayonet locking type. The combination of a small high pressure gold plated contact surface with the locking bayonet fitment, gives an extremely high quality, long lasting electrical contact area. The DNM 3C rotary signal selector switch is fitted with a plastic shaft and all the fixing screws used in our pre and power amplifiers are plastic. Heatsinks The only significant amount of conducting material remaining in any of our products is the aluminium heatsink used on the DNM power amplifiers. To reduce the influence of magnetic interaction caused by such a large expanse of metal, we space the output transistors and regulators away from the heatsink, using aluminium oxide blocks. This material has no magnetic properties but good thermal conductivity. This 5mm non-magnetic spacer gives a big increase in clarity and resolution. Imagine the loss of quality suffered by large all-metal amplifiers!! Would you choose to make a camera out of glass and then fail to notice that the film kept fogging? It is well-nigh impossible to imagine the loss of quality suffered by large solid metal amplifiers! Field Effects Our obsession with stray electromagnetic fields lies at the heart of every component in the DNM range - even our cables, both signal and power supply, are designed to reduce electromagnetic interference as far as possible. The use of solid core cable has significant implications for amplifier designs, as it implies an awareness of the magnetic fields in the cables themselves. After all, viewed contextually, the signal cables are only an extension of an audio amplifier's internal circuits. In fact, failure to take account of magnetic effects has disastrous and irredeemable consequences for sound quality. End Result The end result of this new technology is a range of small, lightweight, audio products, in a market dominated by metal clad monsters. Does this reduce the perceived value of DNM products? Perhaps, but with DNM what you are paying for is the sound quality! To many customers, paying more for a small plastic box seems strange. All other electronics industries have been making their products ever smaller and the smaller they become, the more they cost. Apparently the audio industry is stuck in a time warp!

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