I want to use a 1:1 audio transformer for galvanic isolation of an audio output. I have some 1:1 transformers left that match my requirements, however they have a center tap on both the primary and secondary. I don't "need" these center taps.

What should I do with these CT pins ? Can I leave these pins unused ? should I connect them to ground (what about the isolation then) ? If I use such a transformer with a CT, will it have an impact from a noise/hum perspective ?

Thank you for your help!

  • \$\begingroup\$ think about how the circuit will change if you connect the center tap to ground \$\endgroup\$
    – jsotola
    Oct 31, 2020 at 22:43
  • \$\begingroup\$ Transformers are really low-Fi and typ. capable of 2.5 to 3 decades of frequency bandwidth. Why do you want old school solutions? \$\endgroup\$ Oct 31, 2020 at 23:24
  • \$\begingroup\$ @TonyStewartSunnyskyguyEE75 what are the "new school" approaches you would suggest ? the isolated output will be connected to another device using a 6.35mm TS jack. Thank you. \$\endgroup\$
    – Kraal
    Nov 1, 2020 at 9:51

1 Answer 1


Leave them unconnected then they will have no effect at all on the circuit. Do not connect them to the input ground that will defeat the object of achieving galvanic isolation.


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