powering a large pedalboard

[1878]

Hello Everyone.

I've touched on this previously, but never got to a satisfactory conclusion.

Basically, I run two reasonably large pedalboards consisting of commercial and DIY effects, both of which are powered by their own power supply and daisy chain, but I'm finding the limitations and problems involved in this increasingly... limiting and problematic ??

I've recently come out of retirement from the 'music business' and I'd like to re-evaluate, re-shuffle and re-power my boards. I have a couple of problems though.

1. Some effects don't like to be linked to others via a daisy chain.
2. Differing polarities i.e. Fuzz Face
3. Differing voltages i.e. Valvecaster

After reading this article: http://geofex.com/Article_Folders/Power-supplies/powersup.htm I've come up with what I think would be the best solution for me.





I understand the article mentioned above to a certain degree, but it says near the end that I would have to power everything from 24v. So the questions I have are:

1. Is it worth building in the first place ??
2. Is there a way to do this from a 12v power source ??
3. Has anyone tried a different solution to the one I've proposed ??

I know there are power supplies commercially available that would save the hassle of building these myself but, they're quite expensive, I need two of them and I can't really justify the expenditure for what is now a hobby rather than a job.

Any help would be greatly appreciated.

[composition4]

1. Is it worth building in the first place ?? - Yes, in my opinion.  Reason being that 1. You can build it as you want, and 2. You MAY save money depending on how good at scrounging you are.

2. Is there a way to do this from a 12v power source ?? - I'm not clear on what output voltages you want, I'll assume 9v outs.  First up, to get the isolated outputs you need transformers, and transformers need AC voltage to work.  You would need a 4-secondary-winding transformer or 4 separate transformers to get the isolated outputs as you have drawn them.  So assuming you have 12V AC out from your transformers, you need to convert (rectify) this with a bridge rectifier to DC which will give you 12V x 1.414 = 17V DC.  This is assuming you have adequate filter capacitors after the rectifier to reduce ripple.  But as the bridge rec is seen as basically 2 diodes in series, this will drop that 17V by 2 diode drops, let's assume 1.5V.  So with your remaining 15.5VDC, this will feed a linear regulator which wants its input at least 2V above its output.  And you need to give yourself a bit of a safety gap, because of things like varying mains voltages, poorly regulated transformers etc.  For a 9V linear regulator, you will want 11V on the regulator input.  So your 12V power source is looking fine for this as even after a 1.5V "just in case" gap (my value I choose), you're still getting 14V on the regulator input.  12V regulator should be (just) okay with this too.

Be aware with this though, the input-output voltage difference on the regulator is converted to heat.   If you have a particularly hungry effect that wants say 100mA, the 6.5VDC differential between input and output (15.5V - 9V) is converted to heat (P = VI,  6.5 x 0.1 = 0.65 watts).  This type of heat dissipation will be okay with the TO-220 package, but I wouldn't bother with the TO-92 regulators.

Just a final note, for the daisy-chained effects make sure your transformer is up the current draw AND your regulator is adequately heatsunk for any higher loads.

3. Has anyone tried a different solution to the one I've proposed ?? - Read:  http://www.geofex.com/Article_Folders/Spyder/spyder.htm, which is pretty much more info on the way you're going about it now.  I think you're going along the right track.  Isolated power supplies are the best and most reliable way in my opinion.

Sorry for ranting, really late here and tired.  All of this stuff is in the article on geofex, just thought another explanation may give a different perspective.  Let me know if you have any questions or if I haven't answered something properly.

[Ben N]

Weber has a substantial multi-secondary pedalboard transformer that I imagine would work well for you. I don't know if they are available with a 230v primary, though.

[1878]

Thanks for the replies.

I'm still a novice when it comes to this side of things, but transformers do seem to be the way to go in terms of what I'm after overall. I'm unsure about using them though, as the voltages involved if things go wrong are scary and sometomes death-inducing. I know some may laugh at that but for me, it's like attempting to drive a car when you can't drive. I'll look into it more though. I've found a couple of UK suppliers who stock relatively cheap transformers that are up to the job. I reckon I'd need 6 for each board. 1 for the daisy chain, 1 for positive ground, 1 for 12v and three for problem pedals/spares.

[petemoore]

http://geofex.com/Article_Folders/Power-supplies/powersup.htm
 
RG also offers excellent explanations of the Spyder power supply unit/schematic.

[dudleydoright]

   You could set up your power supply with adequate capacity then use standard DC-DC converters to shuffle things to the values you require. You can get them in regulated, unregulated, step up/down, isolated and non-isolated. They might not list more than 5,, 12, and 24 v outputs but in each product line I've looked at they are almost always offered in more voltages than listed in the supply houses catalogs.
   With isolated regulated converters you create individual dc outputs isolated from any other taps off of your main power (DC) feed. You do need to be aware of your power consumption and size them accordingly. Good Luck.