In previous amplifiers, I used "capacitor multipliers" to smooth the power supply ripple. These required fairly fragile MOSFET circuits which I blew up more times than I can count. For this amplifier, I have decided to replace the elegant, fragile silicon solution with a manly IRON solution - two big heavy chokes. Now that Smith Iron, a subsidiary of Smiths of Weston, is up and running, I will design and wind these chokes myself.

The amp will be pulling a little less than .7A from the power supply. I tried making a choke from recovered laminations from some old rusty transformers I had lying around, but they were pathetic. The permeability of the laminations must have been in the low hundreds; this is contrasted with the brand new laminations that I bought, which have permeability in the thousands, and can generate much greater inductance before saturating.

The design parameters are shown below. I have two bobbin sizes for the 38mm (1-1/2 inch) laminations, so I will use the larger one, to give a stack size of 50.8mm.

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The initial results from my spreadsheet are shown below. If I'm lucky I can get about 1600 turns of 22AWG magnet wire. If I put in a gap of .8mm, I should get an inductance of around 7.5H, which is more than adequate. The flux density calculates around 1.46H, which should not saturate the M6 GOSS laminations that I am using. There will be 1300 feet of wire with an overall resistance of 20R.

Basic Info

OK, let's get winding.