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DIY For Audio
Showcase - DIY LM3886 100W+ bridge/parallel build
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<blockquote data-quote="meshsmith" data-source="post: 876577" data-attributes="member: 15646"><p>Right, first quick tests are in.</p><p></p><p>I'm testing just a single board, so a parallel LM3886 pair driving an 8 ohm load (not entirely ideal, as a single parallel LM3886 is better suited to 4 ohm loads). </p><p></p><p>First thing to note is I get massive hiccups attempting to power on with higher volumes present at the input - for now, the volume needs to be low until the amplifier settles (presumably capacitors charging) and then crank it up thereafter. Almost certainly going to have to build a speaker protection/delayed start circuit to accompany all four amplifiers.</p><p></p><p><strong>Power</strong></p><p></p><p>Right, so I maxed out my power supply before I could get anywhere NEAR clipping. At 3.2A per rail I was getting consistent, clean power using a 1KHz signal, inputting ~1.6V. Yowza. Here's the results of a more standard 1V 1KHz sine:</p><p></p><p><img src="https://i.imgur.com/h0bbYGl.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>30 clean watts, from 2V p2p to 45V p2p.</p><p></p><p><strong>THD</strong></p><p></p><p>Rock, rock bottom, at least in terms of what my equipment can measure. The lab power supply is likely to be cleaner than the average amplifier PSU, so the results may be inflated somewhat.</p><p></p><p><img src="https://i.imgur.com/dNCj8hh.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>-68.41dB equates to around 0.037% THD.</p><p></p><p>So far so good. Next challenge is to sort out the aggressive power-on issue, and finish designing the power supply!</p></blockquote><p></p>
[QUOTE="meshsmith, post: 876577, member: 15646"] Right, first quick tests are in. I'm testing just a single board, so a parallel LM3886 pair driving an 8 ohm load (not entirely ideal, as a single parallel LM3886 is better suited to 4 ohm loads). First thing to note is I get massive hiccups attempting to power on with higher volumes present at the input - for now, the volume needs to be low until the amplifier settles (presumably capacitors charging) and then crank it up thereafter. Almost certainly going to have to build a speaker protection/delayed start circuit to accompany all four amplifiers. [b]Power[/b] Right, so I maxed out my power supply before I could get anywhere NEAR clipping. At 3.2A per rail I was getting consistent, clean power using a 1KHz signal, inputting ~1.6V. Yowza. Here's the results of a more standard 1V 1KHz sine: [IMG]https://i.imgur.com/h0bbYGl.jpg[/IMG] 30 clean watts, from 2V p2p to 45V p2p. [b]THD[/b] Rock, rock bottom, at least in terms of what my equipment can measure. The lab power supply is likely to be cleaner than the average amplifier PSU, so the results may be inflated somewhat. [IMG]https://i.imgur.com/dNCj8hh.jpg[/IMG] -68.41dB equates to around 0.037% THD. So far so good. Next challenge is to sort out the aggressive power-on issue, and finish designing the power supply! [/QUOTE]
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Showcase - DIY LM3886 100W+ bridge/parallel build
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