Most higher-end audio systems have an isolation transformer between mains electricity and DAC/AMP(audio system.)

I know ring transformers havr higher efficiency than E-I transformers.

But noise after through transformer I'm noy sure. (Audio system desires good sinusoid power input.)

I'd like to know which is better suited in an isolation transformer on an audio system.

  • 1
    \$\begingroup\$ Audio system desire good sinusoid power input - that doesn't make much sense. \$\endgroup\$
    – Andy aka
    Commented Mar 11, 2020 at 11:07
  • \$\begingroup\$ @Justme, I think the question is asking about mains transformers and comparing E-I versus torroidal. These will all be isolating type. \$\endgroup\$
    – Transistor
    Commented Mar 11, 2020 at 13:37
  • \$\begingroup\$ @Transistor indeed, OP might not mean isolation transformer after all, but just the transformer of the power supply. Indeed audio gear tend to use toroidal mains transforners for lower output impedance and more controlled stray magnetic fields. \$\endgroup\$
    – Justme
    Commented Mar 11, 2020 at 13:47

1 Answer 1


There is no significant difference between the isolation performance of the two types of transformer, when built with an inter-winding screen connected to earth. This prevents any common mode spikes on the mains supply capacitively coupling through to the secondary.

The symmetrical construction and lack of airgaps in the magnetic path of a toroidal transformer mean it tends to have a lower stray external magnetic field than an EI construction. When properly (uniformly) wound and operated well below saturation, very much lower indeed. Another useful benefit is the form factor, it's often flatter than the EI construction, useful for a thin format power amplifier.

(Audio system desire good sinusoid power input)

Not really, you've obviously been reading too much advertising material for people pushing gold-plated mains fuses, and other ways to part people from as much money as possible.


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