Sowter Audio Transformers (E A Sowter Ltd.)
OCC WIRE OPTION
WHAT IS OCC WIRE?
In 1986 the Ohno Continuous Casting (OCC) Process was developed by professor Ohno of the Chiba Institute of Technology in Japan. The wire made by this process is claimed by our manufacturer to be 99.999 % pure and in our thinnest wire size (50 micron) that it has one crystal boundary per 6.5 km on avearge. Normal wire has a number of contaminants particularly Oxygen, Sulphur, Lead, Antimony and Aluminium and is typically 99.97% pure and has a cristal boundary perhaps every 10 mm.
We have been asked many times over the years if we can wind transformers with Silver, Ultra high purity ("oxygen free") copper or OCC wire. We have always resisted the idea because we dont want to make exagerated claims which we cannot justify.
Recently we made some transformers using OCC wire for one of our highly respected customers who wanted to try them them in his products. He did a side by side comparison of a stereo system which used 3 transformers per channel in the signal path. His conclusion was that there was an unmistakable improvement in the sound from the amplifiers using the OCC wire. The improvement was most noticable in the reproduction of transients.
We do not consider this single result to be significant evidence to make any claims whatsoever as to the benefits or otherwise of OCC wire. This is particularly so because the listening test was not a scientifically valid experiment and as yet we have not been able to make any electrical measurements to back up the observations.
However we feel sure that other customers will wish to make their own experiments and we are delighted to be able to offer versions of some of our standard products made using OCC wire. The wire is of course, much more expensive but for smaller transformers we are able to offer this option for a price uplift of around 20%.
HOW COULD IT WORK?
Perhaps our hearing can respond to "super-sonic" (i.e. frequencies above say, 20 kHz) frequency components present in transients. Perhaps the amplitude and phase of these components can be affected by the wire purity and crystal structure. It would be very interesting if somebody could devise a method of measuring the distortion of transients in music which could be applied to a comparitive test of transformers. Transformers use quite a length of wire so if there is an audible effect it should be possible to measure it.