Custom Transformers

Prem Magnetics is proud to craft custom transformers. We are here to meet your every need with high-quality custom transformers and coils of all kinds. Our team is here to assist throughout the entirety of the custom transformer design-build process. An expert, family-owned manufacturer, we are equipped with the knowledge and experience necessary to:

  • Modify existing transformers
  • Design new custom power transformers
  • Create prototype transformers
  • Provide custom transformer winding services
  • Build new transformers to meet your exact specifications

For all your power transformer design-build needs, we are the first-choice custom transformer manufacturer.

Fill out the contact form below to request a custom transformer design, prototype or build from our team.

Why Choose Prem Magnetics for Custom Transformers?

Prem Magnetics, Inc. offers flexible solutions. We can design custom coils and transformers to your specific parameters or modify any of our existing standard products for your application.

Prem will work with you to provide the best possible custom built transformer at the most affordable price.

  • There is no minimum purchase requirement or nonrecurring engineering (NRE) charge for custom parts.
  • No order is too big or too small — we treat every request with the same care and commitment.

Look no further for custom made transformers and custom coils. With over 40 years’ of experience, Prem Magnetics is the custom transformer manufacturer you can trust.

Custom Transformers Built by Prem Magnetics

Looking for the ideal isolation transformers, DC to DC transformers or single phase transformer winding you can trust? We design and build a wide range of custom transformers to meet varying needs, across industries and applications. Below, we provide details on some of the custom transformers we regularly build for our customers.

Click through the tabs to learn more about the power transformers in each category.

Prem Magnetics is known for its high quality, reliable custom power transformers. Our team will expertly customize or create any of the transformers below to your exact specifications.

  • Linear
  • Single Phase
  • Isolation
  • Switchmode
  • Step Up
  • Step Down
  • High Isolation
  • Printed Circuit Mount
  • Chassis Mount
  • Open Frame
  • Shielded
  • Encapsulated
  • High Efficiency
  • NRTL Capable
  • Standard/Custom Primary Voltages
  • Medical
Custom Power Transformers

Our Impedance Matching Transformers and audio transformers are perfect for use in Voice/Data applications, amplifiers, and more. Choose Prem Magnetics for a high quality, custom transformer to match any load impedance.

  • Telecom Band
  • Audio Band
  • With DC
  • Without DC
  • Printed Circuit Mount (Through-Hole & Surface Mount)
  • Chassis Mount
  • Shielded
  • Encapsulated
  • Laminated Core
  • Ferrite Core
  • Toroidal Core
  • High Isolation
Custom Impedance Matching Transformers

Our custom Line Matching Transformers will perfectly match the output impedance of your amplifier to a number of speakers having various power ratings. Choose a custom line matching transformer for overhead paging and music in any industry or location. Browse existing Line Matching Transformers or get in touch for a custom transformer built for you.


  • 25V Input
  • 70.7V Input
  • 25V/70.7V Input


  • Printed Circuit Mount
  • Chassis Mount

Custom Transformers for All Industries and Applications

We craft high-quality custom transformers for a wide range of industries, including audio, medical, industrial, power and signal applications, and more. Here are some examples of custom transformers we build:

-          Custom transformers for aerospace
-          Audio transformers, audio isolation transformers and audio output transformers
-          Medical isolation transformers
-          Industrial power transformers and electrical transformers
-          Household appliance transformers
-          Transformers for class A and class B fire alarms

Custom Transformers by Class

We build custom transformers to class specifications to ensure safety regulations are met. Our 100% tested custom-made transformers are designed to perform to your requirements. We frequently build the following power transformers and more:

-          Class 2 transformers
-          Class 3 transformers
-          Class H insulation transformers
-          UL Class transformers
-          Safety Extra Low Voltage (SELV) transformers
-          Class B transformers
-          Class 155 insulation transformers

Custom Transformers by Voltage

Tell us your voltage needs and we’ll build the right transformer for you. Some of our most popular custom transformers include:

-          277v to 120v transformers
-          230 to 100v transformers
-          115v to 230v transformers
-          400v secondary transformer
-          120v isolation transformers

Request Your Custom Power Transformer

We build to meet your voltage, output and project needs. From custom class 2 transformers and double insulated transformers, to Ethernet transformers and output transformers, we craft affordable, high-quality custom transformers that are made to last. We also build custom coils, custom inductors and custom assemblies for our customers. 

Located in Johnsburg, Illinois, we are a family-owned custom transformer manufacturer based in the USA, with a global reach. Contact us today to get started with your custom power transformer build, or to learn more about how our custom services can help your business succeed.

Contact us by phone: (815)-385-2700

Contact us by email:


Please complete the form below to request Custom Transformers