helloi
I need to make air core for a quad 405 amplifier. Online calculator can help to find turns number if you know core diameter and wire size.
But how to compute enamelled-wire size ? Do your knowledge help you to choose something between xxx diameter or have you approximative formula enough for audio spectrum?
I need to make air core for a quad 405 amplifier. Online calculator can help to find turns number if you know core diameter and wire size.
But how to compute enamelled-wire size ? Do your knowledge help you to choose something between xxx diameter or have you approximative formula enough for audio spectrum?
The best air core inductors are those who have a wire diameter between turns and the diameter of the whole inductor is the same as its longitude, say, a cubic inductor.
Search in the web or in books, the "Wheeler formula" to design single layer inductors.
Search in the web or in books, the "Wheeler formula" to design single layer inductors.
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Around 1 mm^2 will be fine for 100W into 8 ohms. That's about 17 milliohms per metre of wire, the coil will likely be less than a metre so only a fraction of a watt at full power even allowing for skin effect and proximity effect.
Resistivity of copper is about 1.68x10^-8 ohm-metre, so 1 mm^2 is 1.68x10^-2 ohm/metre, or about 17 milliohms/metre.
100W at 8 ohms is nominally about 3.5Arms max, I-squared-R for 1 metre of wire thus about 0.2W.
Also 1mm^2 wire is rated for 10A continuous, so a generous safety margin.
100W at 8 ohms is nominally about 3.5Arms max, I-squared-R for 1 metre of wire thus about 0.2W.
Also 1mm^2 wire is rated for 10A continuous, so a generous safety margin.