Since the njm4556 are so cheap... class a biasing - diyAudio
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Old 10th September 2015, 10:41 PM   #1
00940 is offline 00940  Belgium
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Default Since the njm4556 are so cheap... class a biasing

Having some fun with ltspice before having fun with Eagle.

The design goals:
- made for 300R headphones;
- a foolproof amp, thx to an output transformer;
- powered from a single 24V rail;
- relatively inexpensive and using common parts;
- limited heat dissipation/power consumption;
- staying in class a at reasonable output levels.

The biasing scheme's inspiration comes from some of jcx's posts. Each njm4556 is biased at about 8ma.

What do you think ?
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Old 11th September 2015, 08:57 PM   #2
00940 is offline 00940  Belgium
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After some fun in Eagle. The pcb is bigger than needed, but that's to fit it easily in an existing enclosure.

The bottom plane is for a lm317 regulator. The blue plane on top is at v+/2 for biasing.
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