Two In One Rehouse - Power Supply

[virginiagentleman]

Hi all,

I'm relatively new to electronics and I haven't totally wrapped my head around some concepts. I'm starting a small project to rehouse two pedals for a friend - he has a cheap delay and phaser (I think danelectro and joyo respectively,) that he wants to put in one box. On the one hand, I figure, seems simple enough, just take them out of their cases, put them in a new double size case, wire everything up -but I'm wondering about the the power supplies. Obviously I don't want to have to 9v batteries/jacks. How can I wire it so that one battery/jack will serve the whole pedal? That is, since they are two different circuits, can one power supply function for both of them, and if so, would it have to be 18v or something? This may illustrate some of the concepts I haven't got down yet, so thanks for your help!

[mth5044]

It becomes easier when you think about it two ways.

The first, consider power supplies that daisy chain the power to different pedals. That is one power supply, powering 2 to a lot of pedals. These are wired in parallel.

Second, two circuits are really just two handfuls of parts. Other circuits are made of a bunch of parts, some even more than both your circuits combined. Just because they are on two seperate PCB's doesn't mean much. As long as they have the same power requirements, you can tread them as one.

So, there is nothing special about powering two circuits at once, just think of it as one effect on two PCBs (that will drain a battery faster). I'd reconsider using batteries anyway. Using the power jack, send power to each pedal. Should be a + and - wire to each board. You can wire up the battery as normal.

[FuzzFanatic71]

Are any of the pedals digital? If so the daisy chaining might cause problems. Usually digital pedals and analog pedals don't like sharing power supplies. This can create noise in the signal. But if both pedals are analog then daisy chain away.

[GibsonGM]

Shouldn't we point out that, just as 'good practice', we might want to somewhat decouple the power supply between effects?

Most designs will have this built-in, so this is likely to be unnecessary to talk about, but - well, it's something that is good to know to look for when you're doing what the OP wants, or if designing your own effect...by 'decoupling network', I'm talking about a reservoir cap on each board, and probably a low-value resistor in series so that any kind of spike (or drop out) that happens on one board doesn't affect the next one.     

Same reason we have a cap to ground on the voltage divider for a bias voltage.  Clean power makes for good audio...

[ashcat_lt]

Assuming that both circuits want the same voltage, it comes down to making sure the power supply can pass enough current for both circuits.  If your power supply is unregulated, it quite likely will give a lower voltage with two circuits connect compared to just one.  How much difference there is depends on how thirsty each circuit is, and how big of a pipe the power supply has.  Yes, that's exactly the same thing as daisy-chaining like we do on a pedal board. 

It's also a good idea to filter (decouple) the power as close to each circuit as possible and maybe even again at the common input point just for good measure.

[antonis]

since they are two different circuits, can one power supply function for both of them, and if so, would it have to be 18v or something?

Only in case of you power them IN SERIES...

(just kidding, of course.. but as mth5044 cleary stated you'll have to power the circuits IN PARALLEL - meaning that you have to share Current - not Voltage)

[virginiagentleman]

Mth5044, thanks, that does make a lot of sense. I will try that.

GibsonGM, when you say make sure there is a 'decoupling network', or to add one - I should be looking for a cap AMD resistor together near where the power supply connects to the board? And if it's not there, how shall I attach it, and what ranges of values should I look for?

Sorry to ask so many questions - I want to not only do the right thing, but know why I'm doing it if possible. I really appreciate the help!

[antonis]

I should be looking for a cap AMD resistor together near where the power supply connects to the board? And if it's not there, how shall I attach it, and what ranges of values should I look for?

It's most possible that the pedals allready have this kind of filter - better manage to find their diagramms than to search items on board..

If not, you can use one leg of a 100R resistor (1/4 - 1/2 W) in series with +9V and a 220μF capacitor between resistors other leg and GND. You'll get the power from resistor/capacitor joint..
(optionally, you can use a 100nF ceramic cap in parallel with the 220μF cap and a 47nF between +9V/resistor leg and GND..)


P.S.
Lazy drawers talk too much...

[virginiagentleman]

Thanks, Antonis! Awesome, that makes sense. Time to get on small bear and grab an enclosure and some knobs!