bcarso
Well-known member
[quote author="Rossi"] The boards would have fit into a much smaller enclosure, there was a lot of space for separation between preamps and PSU section. If I were to design a transformerless preamp I'd make sure the input capacitors were as far from the mains transformer as possible - as was the case here - and I'd also make sure both capacitors get equal exposure. Which is rarely the case.
[/quote]
In addition to the electrical fields for which shielding is pretty easy, the way the balanced circuit intercepts magnetic fields, which are much more difficult to shield from, is crucial. As remarked before, toroids, good thought they are, can saturate on peak currents and radiate like crazy. As well there is always some emission in the vicinity of the leads, and also when there's a significant nonuniformity in the windings.
Then there's the susceptibility to external fields, which dictate careful equipment placement and minimizing loop areas on the boards. Big caps make this tougher.
[/quote]
In addition to the electrical fields for which shielding is pretty easy, the way the balanced circuit intercepts magnetic fields, which are much more difficult to shield from, is crucial. As remarked before, toroids, good thought they are, can saturate on peak currents and radiate like crazy. As well there is always some emission in the vicinity of the leads, and also when there's a significant nonuniformity in the windings.
Then there's the susceptibility to external fields, which dictate careful equipment placement and minimizing loop areas on the boards. Big caps make this tougher.
