Audio transformers based amplifier

[Fernando Barbi]

Hi, this is my first time posting here on the forum.
I'm building a system using 1:1 audio transformers and I'm having hum issues at 50Hz and 150Hz (50Hz is the frequency provided by the power grid here in Argentina). The system is basically a solid-state amplifier stage that saturates the transformers. It has a UTC, a Quad Eight, and a Sony. I've been modifying the transformer positions and haven't gotten much improvement. I'm going to try isolating them with some kind of enclosure. Any ideas? Thanks!

 

[Ike Zimbel]

Welcome! We will need more information to help you.
1) Is the power supply built into the same enclosure as the electronics?
2) If so, the power transformer could be inducing hum into the audio transformers. If that's the case, try inserting a piece of steel between the power transformer and the audio transformers and see if the noise level drops/changes.
3) Did you connect Audio 0v (aka: "ground") to the chassis ground point? This needs to happen in one place or you will get mains frequency hum in the audio.