HIGH FREQUENCY TERMINATION NETWORK (HFTN) A new DNM product improves sound quality   On this Page :   Background    The Problem    The DNM Solution Three DNM HFTNs (the micro-PCBs) seen to the right of their matching plug types Background Audio cables are designed to carry signals in the audible frequency range from 20Hz to 20,000Hz. However cables can easily carry a wider frequency range, from below 20Hz up to and beyond the Super Audio CD (SACD) requirement of 50,000Hz (50kHz), double the highest frequency audible to humans. units for high frequencies, kiloHertz (kHz) thousands of Hertz. MegaHertz (MHz) millions of Hertz. (1 Hertz = 1 cycle per second) the term ‘amplifier’ applies to the power amplifier that drives the speakers, and to all amplifiers used in the audio chain, including pre-amplifiers, output amplifiers in the CD players, D-to-A converters, radio tuners, MP3 players etc. The cable/amplifier problem When the cable is connected to an amplifier, it encounters even higher frequencies that cause significant degradation of the audio signal quality. Audio amplifiers drive RF (Radio Frequencies) as high as 100MHz into the cable which are high enough to stimulate the cables transmission-line effects. The RF signal is modified by resonances in the cable, then non-linearly processed by the amplifier feedback system, to produce audible interference. NB : Feedback is used in amplifiers to define gain and reduce distortion, it is generally accepted that it improves amplifier performance without adversely affecting sound quality. Easily measured evidence of the RF contribution of the cable is the large variation of its electrical impedance which swings sharply from less than ten Ohms to several thousand Ohms many times across the RF range. NB : Jim Lesurf confirmed this effect in his article "Taking the Lead" here. Uneven RF impedance, due to resonance, occurs in all interconnect and speaker cables. Each cable design has its own unique resonance pattern, so it degrades the amplifier signal in a specific way. Consequently all cables add some high frequency glare especially to digital signal sources, and all cables cause some loss of audio clarity. This complex interaction between cable and amplifier is the primary cause of the sound differences heard in audio cable comparisons, differences that are described by cable makers to be "the sound of the cable". The DNM solution: the High Frequency Termination Network (HFTN) DNM research has shown that it is possible to significantly reduce the problem by controlling the RF termination of the cable, to prevent interaction at frequencies that affect the amplifier NB : Before transistor amplifiers were made, impedance matched connections were widely used with valve electronics, mainly to avoid signal loss, but in modern hi-fi systems this discipline seems to have been forgotten. The DNM HFTN is a precision circuit fitted at each end of the cable. It levels severe impedance dips and peaks in the cable whilst remaining absolutely transparent to audio signal. The amplifier-to-cable interface is therefore improved by the HFTN, giving more audio clarity, greater image depth and delicacy of sound. The sound quality improvement with digital signal sources is substantial. Limitations of use The HFTN is designed to work with amplifier source impedances ranging from very low values up to 200 Ohms. Amplifiers with unusually high source impedance (e.g. valve types with 1000+ Ohms impedances) may not benefit from the HFTN. Built on micro-PCBs, HFTNs are small enough to fit inside the interconnect cable plugs. They can be assembled (only by DNM Design) onto existing DNM Stereo cables or fitted as an optional extra on new DNM Stereo cables. Each HFTN costs £42-00 (inc. fitting), so the four HFTNs (required for a stereo interconnect cable) add £168-00 to the ex-VAT price of the cable and plugs. However, customers should find that the HFTN is excellent value because the sound improvement is substantial, so a DNM cable with HFTNs is unlikely to be equalled on sound quality by a non-terminated cable, even an extremely expensive one. Available from the DNM Online Shop :- HFTNs to fit all our interconnect plugs :- the three (RCA) phono plug types, the DIN plug and the (balanced) XLR connector.   BRAND NEW and just now available from the DNM Online Shop : A pair of the larger SPEAKER HFTNs just announced. These work in parallel with your existing loudspeaker cables. These NEW HFTNs are very easy to fit because they work in parallel with your speaker cables. Full details of this new product here (This document is also linked from the HFTN page of our online shop).

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