Ok... you know those little current doubler adapters for power supplies...?

Cirrus

If you plug them into two isolated 100ma outputs on a power supply you get one 200ma output. Or use the high current 250ma outputs together and get 500ma.

I'm happy with that.

What if you plug it into a 250ma and 100ma output? What do you get?

What if you plug one into 100ma and 250ma output, then plug a second current doubling adapter into the output of the first one plus the other 250ma output?

Background: I have a pedal that claims 600ma required, and It'd be nice to power it with the PP2+ on my board.

Sporky

Cirrus said:

What if you plug it into a 250ma and 100ma output? What do you get?

What if you plug one into 100ma and 250ma output, then plug a second current doubling adapter into the output of the first one plus the other 250ma output?

350mA, 600mA.

As long as the outputs are the same voltage and genuinely isolated, the current just adds up. Like putting batteries in parallel.

Cirrus

Ok, that's what I hoped - I just wanted to be sure it was clever enough to not try to pull the same current equally from every supply and blow the lower rated one. Actually quite curious what the mechanism is there, if anyone can explain?

thermionic

Kirchoff's Law.

Sporky

Bless you.

ICBM

Cirrus said:

Ok, that's what I hoped - I just wanted to be sure it was clever enough to not try to pull the same current equally from every supply and blow the lower rated one.

Actually I'm not 100% sure that isn't the case. I think it depends on the internal resistance of each supply - if all of them have the same internal resistance then it will indeed draw the same current from each, and would overload the lowest-rated if the total current draw was more than lowest-rated x number of outlets.

What I would do first is measure the current draw of the claimed 600mA pedal - often they're a bit exaggerated. (Sometimes a lot.) If it's under 500mA then it doesn't matter because it's safe to use two 250mA outlets.

clarkefan

Just curious, can I ask, what's the pedal?  Sounds like a lot of current requirement!

Sporky

ICBM said:

Actually I'm not 100% sure that isn't the case. I think it depends on the internal resistance of each supply - if all of them have the same internal resistance then it will indeed draw the same current from each, and would overload the lowest-rated if the total current draw was more than lowest-rated x number of outlets.

Good point.

I think the PP2+ uses one transformer with multiple output coils. Though I can't now work out the implications of that.

Cirrus

clarkefan said:

Just curious, can I ask, what's the pedal?  Sounds like a lot of current requirement!

A Korg SDD 3000. I concur totally with ICBM that quite often they actually draw less, my plan was just to use the two 250ma outputs together and check they're not getting too hot after a couple of hours of rehearsal. My question was more a theoretical one because I didn't know the mechanism behind it.

I think quite often with digital pedals peak current draw is at startup, so I guess if it goes over *a little* for like half a second while it flashes all the lights and boots up that's not going to damage things.

I've actually powered a Zoom CDR-70 from a single 100ma output for a couple of years (it claims it needs 500ma but someone measured 135 as a realistic maximum) and a Line 6 G30 receiver which draws about 150ma and never had any problems, I'd guess VL rate them quite conservatively...

vasselmeyer

Same here. I have a Zoom G3 that says it needs 500ma and it runs quite happy on 300ma. I do have to switch it on after the other pedals though; it sems the initial surge when the whole board it switched on is too much for the power supply.

Sporky

Cirrus said:

my plan was just to use the two 250ma outputs together

That sounds like a good plan.