Chapter 16

Power Supplies

“We thought, because we had power, we had wisdom.” Stephen Vincent Benet: Litany for Dictatorships, 1935

Power for Phono Preamplifiers

Moving-magnet cartridges generate small signals, at about 5 mV rms, while moving-coil cartridges give even smaller ones, down to 50 uV in some cases. This might lead you to suppose that very clean power supplies are essential to get the best noise and hum figures, but as with so many things that seem obvious in audio, it is not the case. I have designed many phono preamps that were powered directly by 78/79 or LM317/337 type IC regulators, with no additional filtering. In no case did rail noise or ripple make any detectable contribution to the output. To give this some perspective, ...

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