Kettle Leads: An Audiphile Study

I have in recent months been interested to read many accounts of studies examining the influences of different aspects of A.C. mains power supply on ‘high-end’ audio equipment. An unpolluted supply with adequate current provision, ideally from a separate spur and perhaps via an isolator or mains cleaner is advised, possibly even complete replication of the 50Hz, 240v current having rectified and cleaned the domestic supply. Type and configuration of the mains cable to each component in the audio chain has also quite rightly come under scrutiny and recommendations of differing levels of conformation and expense have been made.

Recent purchase of a pair of hand-plaited, heavy-gauge silver-plated oxygen-free copper mains leads (for only £500, with a couple of accessories thrown in) led me to carry out some experiments of my own. The plaiting together of two sets of conductor and earth cables in each of the two leads was with the aim of reducing radio-frequency radiation by cancellation within and around the individual leads, thus reducing the propagation of radio-frequency interference in the associated audio equipment.

Examination of my audio equipment revealed several items which might benefit from optimal mains cabling, all utilising connections of the IEC 3-terminal variety: the so-called ‘kettle lead’. My intention had been to experiment by substituting the lead from my kettle for others supplying the audio chain: I was thwarted in this endeavour as my ‘high-end’ Dualit kettle has a captive lead to its base. However, a search of my garage revealed a Russell-Hobbs automatic kettle, which while from a more modest price-point is probably more typical of that found in less pretentious English audiophile homes.

The ideal audio apparatus for my experiments was clearly the power amplifiers, as there are a matched pair of them (AVI monoblocs) with a high current requirement and separate leads. One of the plaited leads was therefore left supplying one amplifier, the other lead being exchanged with the kettle lead.

Initial results were inconclusive. While subjectively the time for the kettle to boil seemed extended, checking time from switch-on to automatic cut-out (this latter a boon to the serious experimenter) with a chronograph showed no change. Substitution of an electromechanical Porsche Design IWC chronograph for the mechanical Omega Speedmaster (the first –and only – watch worn on the Moon) gave the same result. The delayed boil – even if only a subjective impression – must however be considered a disadvantage.

Moving on to the main object of this research, additional apparatus was installed. Most experiments used a solid silver tea-pot (London hall-mark, unknown maker, 1934) and leaf tea (Assam or Lapsang Soochong, Fortnum & Mason) with Tetley’s tea bags brewed in a mug (Esso garage, special offer) as a control. Earl Grey tea was considered but rejected as the scent and flavour of the oil of Bergamot, which forms part of the recipe, might mask subtle changes, and I don’t like it anyway.

Results were quite unexpected. Tea brewed in the silver pot was always preferred by this observer, while an independent observer for whom this was a ‘blind’ experiment preferred the ‘bag’ tea, but insisted on making her own. She reasonably points out that I have not had proper training in this technique, but felt by the end of the day that I had gained a fair grasp of it. (Although difficult, it is of less complexity than – say – setting up a tone-arm). We both unequivocally preferred the tea made using the ‘high-end’ cable: the appearance of the brew was clearer and brighter, as were the ‘top-notes’ of the flavour. The mid-band of flavours was more distinct and the lower flavour band, the ‘body’ of the tea was better defined and less ‘muddy’ both in appearance and taste.

These findings I feel could quite easily be attributed to the effects (described in several articles I have read about signal leads) of ‘metal synergy’ where the same conducting metal is used throughout the signal pathway, source to amplifier, amplifier to loudspeakers, with benefit. In this case, the use of a silver-on-copper mains lead and a silver tea-pot could confer similar advantages, although this does not explain the benefits to ‘bag-in-mug’ tea. This may be comparable to the results often described where a loudspeaker known (in systems of moderate ability) to be a modest performer shows unexpected quality when driven by an exceptionally good amplifier and front end. The results with tea made from a ‘mass-market’ tea-bag directly in the mug were certainly startling: clearer, less coloration, better balance across the flavour spectrum. My independent observer considers that the differences noted could be explained by systematic error, as the OEM lead tea was left to stand while the specialist lead tea was being made, both being tasted together. She described the flavour of the original teas as ‘stewed’.

While subjectivism in evaluation has a place, it must not be allowed to mask the benefits of the scientific method.

During consumption and evaluation of the tea, I listened to the wireless, both on FM and via a DAB tuner. No differences were noted in channel balance, volume or coloration despite the differences in mains lead of the monobloc power amplifiers. Little difference was found between either source, except for the exasperating difference in timing, DAB being measurably slower. It is in fact subject to about a second’s delay in broadcast and processing, making meaningful A:B comparison impossible. Both sounded very satisfactory.

In view of these findings it is proposed to repeat these experiments using coffee. I hope to find a Sheffield Plate coffee-pot, further to explore metal synergy, as the construction material (a silver-copper-silver sandwich) resembles the silver-plated copper of my mains leads.

  • No animals were harmed in this study.( If my dog dislikes the music, he leaves the room.)
  • Conflicts of interest: none. All the equipment used is wholly owned by me. Taste-buds and ears alike have been calibrated by years of abuse.
  • Equipment used: AVI DAB & FM tuners, AVI Integrated Amplifier, AVI monoblocs. Quad ESL63s, Rogers LS3/5a (15ohm), AVI Neutron iv. Cables: as described. Interconnects & speaker cables: Chord. Kettles by Dualit & Russell-Hobbs. Tea: Fortnum & Mason, Tetley.
  • Chronographs: Porsche Design (IWC) & Omega Speedmaster.
  • Assuming the benefits of ‘metal synergy’ to be demonstrated, the ideal match for a silver-plated copper kettle lead could be predicted to be a Sheffield plate tea-pot, although the traditional process involved rolling sheets of silver and copper together under pressure rather than electroplating. Most Sheffield plate seen today is somewhat worn, but remains reassuringly expensive.

By Dr A.P.S.Kimberley, M.B.,B.S.,F.F.A.R.C.S.,F.R.C.A.,M.R.I.