[DIY Bassdrum] 220uF electro's? Caps need to be this big?

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DJMaytag
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[DIY Bassdrum] 220uF electro's? Caps need to be this big?

Post by DJMaytag » Fri Jun 02, 2017 8:29 am

The two caps on the power rails... 220uF seems excessive. The biggest caps I see in these spots are 47uF, while most other projects I see 10 or 22uF electro's there. Can smaller ones be used, or is there an actual need? Was this used in the original 808 circuit?

There's a third 220uF cap, that is connected to the +5V regulator. For a lower voltage, I can see a need for a bigger cap, but still... 220uF?

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Post by hexinverter » Fri Jun 02, 2017 5:21 pm

You can use a smaller value! No problem. It'll actually lower inrush current which might be a good thing depending on your PSU you're powering with. I made 'em pretty big on the DIY since, well, it's DIY and you can adjust to your needs. If you have a noisy as heck PSU, for example.

Anyway, anywhere in the realm of 22uF+ should be good. There's a lot on the Mutants that aren't on the 808 since they're powered by eurorack supplies instead of a specifically designed PSU for a single drum machine. And well, all of the trigger conditioning/accent stuff/etc. to make them work in modular at all. So it's not really quantitative to compare to the 808/909. But yeah, they had some big caps on the main linear PSU and then smaller ones dispersed throughout the massive PCB near each drum circuit.
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Post by DJMaytag » Sun Jun 04, 2017 3:40 pm

Cool, thanks for the heads up on this! There was a FB discussion on the Synth DIY group about these power rail caps, and how inrush current can get pretty huge if you have a lot of modules with really big power rail caps. This is why I ask, even though I likely have a huge enough linear supply to handle it.

I also ask because I mistakenly ordered some 220uF's from Tayda that were HUGE, as in totally unusably huge. Got out a caliper and found some 220uF's at Mouser that'll fit, but I might go ahead and use the standard 22/47uF's I've been using in about every module I've made thus far.

Thanks again!

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