High-current pedal board supply

[greiswig]

Hi, all,

My current pedal board uses a Dunlop DC brick, which does just fine with the pedals that I have currently (no puns intended).

But...I'm also getting an Eventide Timefactor, and although I don't know how much power it actually draws, the supply that comes with it is rated 9V at 1200ma.

If I had my ideal, it would be something along these lines: get a power supply for the DC Brick that is beefier (2-3 amps at 18V), and make whatever circuit mods might be needed on one of the isolated 9V outputs such that it can supply the Timefactor. A laptop power supply, for example.

Anybody else ever done something like this? What kind of mods might be needed? Any suggestions or help are welcome!

Best,

-g

[greiswig]

Ah, probably not worth it. The heart of it seems to be a Maxim max830cwe which is only rated at 1A. So I'd at least have to replace that, and I don't know of something with that same form factor that would fit the bill of 2A rating and 9V regulated output.

I don't even know how the outputs (supposedly "isolated" from one another) really are...the only thing I notice that seems unique to each output is an electrolytic cap and a 2ohm resistor.

[Cliff Schecht]

I would guess it's a flyback SMPS with independent windings for each 9V rail. I haven't seen the insides so that's only a guess..

[paulster]

The DC brick doesn't have properly isolated outputs.

I've got a Burkey Flatliner Pro, which does (and weighs a ton to boot) and it has individual taps for each output on the transformer and a bridge rectifier, filter caps, regulator, current limiter and post-regulator filter per output!

[Cliff Schecht]

The MAX830 is a simple buck regulator so that makes sense. You don't need isolated outputs with guitar pedals anyways, you just need to control the grounds properly to prevent excessive ground loops. The smart way to handle pedals is to only have one of the pedals grounded to the power supply, you use the in/out jacks for all other grounds.

A flyback would be a very elegant solution as well, completely isolated outputs with the highest current drawing pedal going on the regulated output. Any auxiliary voltages that one needs could be achieved by adding another set of windings to the coupled inductor. The only downfall is actually having that coupled inductor manufactured would be expensive and winding it yourself can be quite tedious, especially if you're using interleaving on the windings.

[greiswig]

The smart way to handle pedals is to only have one of the pedals grounded to the power supply, you use the in/out jacks for all other grounds.

Interesting! So most/all pedals have chassis ground connected to battery negative? If so, I wonder if it would be just as easy to simply make a row of jacks, each connected to the same regulated supply, and just have the one (required) with negative to the sleeve. Throw a ferrite bead and maybe a cap on it at the tail end, and call it good?

[martin manning]

Seen this?

http://www.geofex.com/article_folders/spyder/spyder.htm

The Weber transformer mentioned is $25 now, but it has a 9 isolated secondaries, 8 @ 11VAC, 300ma, and one @ 9VAC, 2A.

[Structo]

I helped a guy build one of those supplies with the flat pack transformers.
Worked pretty darn slick.

[Structo]

Interesting! So most/all pedals have chassis ground connected to battery negative? If so, I wonder if it would be just as easy to simply make a row of jacks, each connected to the same regulated supply, and just have the one (required) with negative to the sleeve. Throw a ferrite bead and maybe a cap on it at the tail end, and call it good?

Not all pedals are negative ground.
The old PNP Fuzz Faces are a good example of that.
Fortunately most pedals these days have the negative ground system.

There are a couple different power supply versions out there.
The older pedals used more primitive version of supplies.
There are non-regulated and regulated supplies.

Here is some good info and he has the current draw of a lot of pedals.
Some good reading for sure.

http://www.stinkfoot.se/andreas/diy/art ... sadapt.htm

http://www.stinkfoot.se/info/psu_en.htm

http://www.stinkfoot.se/andreas/diy/diyhome.htm

http://www.stinkfoot.se/andreas/diy/power/list.htm

[Cliff Schecht]

If you use an isolated supply then the funky grounding scheme on Fuzz Face is no problem. It's only when they aren't isolated that you get problems.

[greiswig]

Seen this?

http://www.geofex.com/article_folders/spyder/spyder.htm

The Weber transformer mentioned is $25 now, but it has a 9 isolated secondaries, 8 @ 11VAC, 300ma, and one @ 9VAC, 2A.

Nope, hadn't seen that. But it looks like the Weber xformer is not really designed to provide a 9VDC supply over 300ma, unless I'm missing something?

[ampdoc1]

Not sure what kind of pedal might take >300ma to operate! But if needed, you could parallel as many of the 11VAC secondaries as you wish to up the current requirement.

a'doc

[Cliff Schecht]

Digital effects can take up to 2A+ to run! He was saying he had something that takes 1.2A which is common, my Line 6 FM4 takes a 1.2A supply.

[greiswig]

So, again, is it possible to do this with a single regulated power supply, avoiding ground loops by having the sleeve of interconnects only connected to one of the two plugs?