Technology: Toroidal Audio Transformers

Essentially, transformers are devices that consist of two or more coils of wire that are wound on a common magnetically conductive material (the core). When alternating current flows in one coil it creates a magnetic flux that flows through the core and engages the other coil(s) in which it induces a corresponding potential. If the second coil [referred to as the secondary winding(s)] have more turns than the first coil (referred to as the primary winding) the induced voltage is proportionately greater and it is referred to as a "step-up" transformer.
     In the electrostatic speaker, in order to develop an adequate electrostatic force to produce acceptable sound, the audio signal from the amplifier must have a amplitude much higher than that supplied by the power amplifier. Therefore, a "step-up" transformer is used to accomplish this.
     The accuracy with which the secondary voltage follows the signal voltage applied to the primary coil is of prime concern. The magnetic core that couples the primary and secondary windings holds the key. Both the type of core material and its geometry are important. Assuming that the best core material has been selected, the next choice is how the core is constructed. In audio work cores are normally fashioned in thin layers (laminations) rather than having a solid mass. This enhances high frequency coupling. However, it also invites small air gaps between laminations, which result in magnetic leakage and an increased resistance (reluctance) to the flow of magnetic flux. All magnetic core materials exhibit non-linearity, which means that doubling the voltage to the primary coil does not double the voltage induced in the secondary coil. This effect generally gets worse as the signal level is increased. This is referred to as magnetic saturation of the core. Proper choice of the core material reduces this effect to a non-detectible level. There are other core parameters of a lesser nature that affect coupling accuracy which are not of first-order importance to this discussion.
     The combination of magnetic leakage, reluctance and saturation effects result in a loss of accuracy in the induced secondary voltage. After selecting the best core material, the core geometry is then chosen. Most common transformers use discrete laminations that are stacked upon one another to make a core. This type of transformer is the cheapest to manufacture. Unfortunately, this approach exhibits a relatively loose magnetic coupling between coils and therefore is not the optimum core geometry to use to attain the best coupling accuracy. One type of core geometry has been found to offer the least magnetic losses and affords the best (tightest) coupling accuracy. This geometry is referred to as the toroid. In effect, a toroid core is formed by taking a long strip of magnetic material and rolling it into a tight coil that resembles a doughnut. The primary and secondary wire is wound through the center hole and around the core and back through the hole, etc., to form a coil. This approach provides the least losses and the tightest coupling possible since the core is one piece rather than a (leaky) stack of separate pieces.
     The toroidal transformer is more expensive to manufacture than the stacked type. However, in the quest for highest signal accuracy, there is no substitute. The toroidal core requires less energy to produce magnetic coupling between coils and therefore provides the ultimate in low-level signal resolution and signal purity. Delicate sounds are significantly more realistic with toroidal technology. For example, the decay of acoustic energy in a hall following a loud passage seems to reduce in level seemingly forever. The nuances of overtones are much more apparent and add greater realism (such as the breathiness of the voice or the surface texture of a stringed instrument) approach that of the original sound. Recording engineers have mentioned to us that by using our toroidal technology they have heard very low-level extraneous sounds outside the recording studio never detected before in their recordings such as traffic, dogs barking, aircraft flying over, etc. More than one reviewer has told us that we should never use anything but toroidal technology in our speakers. If toroidal technology were more affordable, we would do just that. It was developed for our ULTIMATE speaker series but we have made it an option on all of our products for those who wish to have it. Let’s just say that the toroidal audio transformer brings music reproduction another significant step closer to the original sound.