There have always been many views and opinions on what is the best type of AC power transformer for use in high-end audio equipment. The debate has always been strongest around the selection of transformers in audio amplifiers, as this is where a weakness in transformer performance can manifest as hum.
Higher Price Means Quality?
Historically, toroidal transformers have been more expensive, and perhaps this resulted in the commonly held assumption that they provided better performance in all aspects. Their higher cost can be attributed to the greater manufacturing effort, as they have traditionally had to be hand-wound. The toroidal design certainly has advantages, but so does the traditional laminated style.
Comparing Laminated with Toroidal in High-End Applications
The toroidal transformer has the advantage of being very efficient. When comparing similar powers, the toroidal design results in a smaller and lighter transformer. Another advantage is that they operate at a lower temperatures. The toroid transformer also emits fewer stray magnetic fields, which results in a lower screening requirement. These are common reasons why they are used in high-density small applications. Under low load they also have very low mechanical hum – hum from the chassis rather than the speakers. They are also easier to mount using a single bolt.
One disadvantage of the toroidal is that they are not good if you have a DC offset in your mains AC supply. When a DC offset occurs in a toroidal, the transformer will mechanically hum and generate noise in the power supply output. Laminated transformers do not suffer any issues when DC offset is present. This is a major advantage for the laminated transformers. However, they have the issue of the stray magnetic fields that cause audio hum when reaching the audio signal circuits.
The main trade-off, when designing for ultimate performance, is between the ability to handle DC offset against the number of stay magnetic fields that have to be protected against.
Many transformer manufacturers, such as Siga Transformers, make both types of transformers for numerous applications and markets.
When selecting components for your next project or selecting equipment based on the components they contain, it is important to recognise that both types can deliver outstanding performance. A well-designed and well-made transformer of one type will always out-perform a standard version of the other.
