A New Zobel Network for Audio
A new class of Zobel network1 has recently been developed for assisting in RF & EMI suppression and spike risetime reduction, and overall offers consequent noise-floor reductionin the audio circuits associated with the device. A commercial realisation dedicated to mainly dealing with amplifier-to-speaker connections is named Zapperator. A complementary device incorporated into cables2, and so particularly suited to line- and vinyl/cartridge-level connections, is Mini-Zapperator.This cable-integral version is particularly effective above SHF (above 800MHz). Availability is restricted to world-class woven Kimber cables, as available from Russ Andrews Accessories Ltd.
It may be interesting to learn that Otto Zobel1 did not specify the name for the network generically known as ‘Zobel’, and the title 'Zobel' or 'Zobel network' is largely limited to audio power electronics, and immediately related fields. Elsewhere, the same arrangement may be merely titled 'RC' network, or 'RC damper' or 'damping network'; or in more industrial cases 'snubber'. At the same time it fits naturally at the base of an entire family of dissipative filtrative networks he did invent, that also bear his name. But these are now largely forgotten - he is far more famous because of the beneficial applications for Zobels in well-engineered audio circuitry, particularly where there are solid-state circuits and/or loudspeakers. However, it is useful to realise that a Zapperator should not be confused with a loudspeaker Zobel network3; nor the Zobel that is de rigeur to stabilise most solid state amplifier outputs7.
Any form of Zobel-type network connected across an audio line must be subtle. For any high resolution music reproduction system, brute force component value scaling which remotely 'clamps down' on hf extension, or musical dynamics, is ill-advised. Brute force attenuation of RF would amount to applying higher capacitance, lower resistance, or worse, both at once. See the later section 'Some Audio quality considerations'.
When compared to a standard 'Zobel' network4, the new class of Zobel network offers its improved performance with no increase in the overall capacitance and resistance employed across the line.Therein lies just one reason for its enhanced performance.
© November 2009 Ben Duncan Research - UK & Russ Andrews Accessories Ltd
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