Power supply for a modular instrument question

[obs]

Hi all,

I'm building a modular system composed of basically whatever circuits I like, and feel would go well the other modules (ie guitar effects, mixers, circuit bent stuff,  oscillators, filters).  Everything, except some circuit bent keyboards is powered by a 9v battery current.y, but I am realizing that this method wastes space and is impractical.

I'd like to use a 9v ac converter that plugs into the wall as power source that I could just daisy chain to all of the various modules.  however, I think this might risk some sort of AC carry over between the circuits.

I've read some articles online, and it seems that it could work if I used a decoupling cap, like .1uf, going from + to ground at the power input of the circuit to block AC.  Am I understanding this correctly, and would this be a feasible approach?

[expanoncolin]

Hi all,

I'm building a modular system composed of basically whatever circuits I like, and feel would go well the other modules (ie guitar effects, mixers, circuit bent stuff,  oscillators, filters).  Everything, except some circuit bent keyboards is powered by a 9v battery current.y, but I am realizing that this method wastes space and is impractical.

I'd like to use a 9v ac converter that plugs into the wall as power source that I could just daisy chain to all of the various modules.  however, I think this might risk some sort of AC carry over between the circuits.

I've read some articles online, and it seems that it could work if I used a decoupling cap, like .1uf, going from + to ground at the power input of the circuit to block AC.  Am I understanding this correctly, and would this be a feasible approach?

You should be fine using a single 9V DC source, but yes, you should include .1 uF and 10 uF decoupling caps on each circuit.  For the non-9V circuits, you should use an appropriate voltage regulator.

-Colin

[obs]

Thanks!

Could you explain the reason for why there should a .1uf and 10uf decoupling cap?  I assume the 10 uf would be polar, but what would be the difference in implementation for each?  I've done a bit of research on decoupling caps, but i'm still a bit confused.

[BrassTeacher]

One thing that will be essential, add up the current draw, i.e., the number of mA each device requires, and make sure the wall-wart you use is capable of feeding a MINIMUM of the total amount of current. I would recommend making sure whatever power supply you use is capable of at least TWICE the total amount of current required. This is for many reasons: Safety (you want plenty of headroom to prevent overheating), current/voltage stability (related to that headroom thing again), and longevity of the power supply.

As for the 10µf cap, it need not be bipolar, just make sure the negative side, which usually has a stripe, goes to ground. Use a cap rated for 16 or 25V.

Oh, one more thing: These are not that common, UNLESS it is a stomp-box or older Korg power supply, but some 9V power supplies have the center of the connector carrying the negative (ground) voltage. The most common 9V power supplies use the center of the connector as positive. It is possible that you will have a mixture of "modules" that are center-negative and center-positive.

I wish I could remember the name of the company that makes a power supply specifically to daisy-chain a full board's worth of effects pedals together, with only one wall-wart. "One Spot" I think is the name, but don't hold me to that...

[obs]

Ha, yes, thats the power supply I ordered, because it has a 1700mA current.  I think that should be sufficient for a whole bunch of modules.