Multi-effects, power and isolation: supply rail decoupling ?

Putting two effects in one box almost looks too easy, but you will save a lot of time reading the frequent questions before starting such a project...

Multi-effects, power and isolation: supply rail decoupling ?

Postby Cub » 07 Mar 2012, 20:04

Now then lads,

Just had one of those lightbulb moments. Trying to cram a bunch pedals and a power supply on a shelf in my rack might not be such a brilliant plan after all. The enclosures take up a lot of room with all the space they need for batteries and footswitches, features that will be useless to me once I get everything hooked up. So instead of that, I might as well buy a rack-mountable enclosure to rehouse the effects I already have and don't bother with enclosures for the ones I still have to build.

That's all very nice, but then comes the tricky bit. Or at least, tricky to me: getting power to these effects in a way that doesn't introduce any unwanted noise. Can I get away with using a single powerful power supply and applying supply rail decoupling (100r + 100 or 220 µF ?) or should I do something else ? I could stick a Pedal Power or a different power supply unit in my rack, or buy proper loads of individual transformers to build something like the GEOfex Spyder.

thank you for your help !

Cub
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Re: Multi-effects, power and isolation: supply rail decoupli

Postby Cub » 09 Mar 2012, 10:14

Perhaps it's worth mentioning that all sorts of different things will need the juice. A Silicon Tone Bender and maybe a Fuzz Face, definitely a Klon and possibly one other pedal that uses a charge pump. Also, a Big Muff and a pedal to boost that Muff: SHO, LPB-1, RAT, another Muff or even a n00bscreamer ? Still out on that one.

Lastly, I might have to find a (digital) reverb that does a better job of getting that "drippy" sound than the spring reverb in my TC Electornic G-Major 2.
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Re: Multi-effects, power and isolation: supply rail decoupli

Postby hamilcaster » 20 Mar 2012, 21:50

Hey there. I'm building a similar thing with twelve circuits and an internal power supply inside an aluminum box. My xfrmer is a Weber, is an EI type with 8 11vac secondaries and 1 9vac. several of the pedals will share the same secondary while others like a digital reverb will gets its own. I too am trying to learn how best to decouple the shared circuits. I'm thinking each circuit will gets its own regulator and smoothing caps... Do you know much on the topic?
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Re: Multi-effects, power and isolation: supply rail decoupli

Postby Zokk » 21 Mar 2012, 01:02

If several circuits are going to be fed by one common secondary, I would suggest one regulator (LM317T) + necessary diodes rectifier, resistors and cap filtering, then add say 100uF or 220uF per circuit in a star configuration. It should be ok like that.
You could use the same configuration as on my 9V psu board for the regulators if you want a fixed voltage:
viewtopic.php?f=28&t=13157

You could build a kind of distributor board but only if the connexions are short, if not it is best to put the 220uF caps just in front of the circuits.

Be careful with your positive ground circuits, they could share the same secondary but avoid mixing positive ground circuits with negative ground ones.
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