How to power multiple devices with a single SMPS?

Thread Starter

benstat

Joined Sep 16, 2021
7
Hi,

I'm looking for some advice about power supplies that I've struggled to find elsewhere (ie. Google/YouTube).

I have a bunch of music gadgets (synths, effect pedals, etc) that all have 'wall wart' power supplies. I decided to research the possibility of making my own 'master' power supply for at least some of my devices, to reduce the clutter.

I'm thinking of buying an AC/DC 12V/20A switch mode power supply such as this:
SHNITPWR 12V Power Supply 20A 240W AC DC Adapter, 110V / 220V AC to DC 12 Volt 20 Amp Switching Power Converter Transformer LED Driver for LED Light Strip 3D Printer CCTV Security System LCD Monitor: AmazonSmile: Electronics & Photo

It has "Three sets of output channels available" (that is, 3 x COM & 3 x +V terminals).

Can I connect more than 3 devices to it? IOW, can I connect 2 or more devices to the same terminals, and if so, does that affect voltage/current in any way?

A more pertinent question might be, is there a recommended way to distribute power to multiple devices from a single SMPS? Some kind of module I could connect to give me, say, 6 channels? This embedded SMPS has something along those lines, but I've no idea what it's called:
RS PRO Embedded Switch Mode Power Supply SMPS, 12V dc, 20A, 240W Enclosed | RS Components (rs-online.com)

Any advice would be much appreciated.

Many thanks in advance,
Ben
 

LowQCab

Joined Nov 6, 2012
1,183
Pedals are usually 9-Volts, but a few are 18-Volts.
You didn't specify what the Voltage requirements are for every device.
Are they all polarized the same ?
Do You have Wiring with Plugs already installed.
Do any of them "not" run on a 9-Volt Battery ?, (special Voltage requirements ?)
Have You checked the amount of Current required by each Device ?
( It should be listed on the Wall-Wort, or the Owners-Manual )
.
.
.
 

Thread Starter

benstat

Joined Sep 16, 2021
7
Pedals are usually 9-Volts, but a few are 18-Volts.
You didn't specify what the Voltage requirements are for every device.
Are they all polarized the same ?
Do You have Wiring with Plugs already installed.
Do any of them "not" run on a 9-Volt Battery ?, (special Voltage requirements ?)
Have You checked the amount of Current required by each Device ?
( It should be listed on the Wall-Wort, or the Owners-Manual )
.
.
.
Thanks for the quick response. Perhaps I should have said that I've already researched the voltage/current/polarization requirements of each device (I have a spreadsheet, lol!).

I decided to keep it simple to start with (since I'm a complete noob), and power 4 synths from 1 supply, all of which are 12V center positive, drawing either 1.2A or 1.5A. Hoping that's a sensible/simple/safe starting point.

If that's successful, then I might do the same with my 9V and 5V devices (nothing over 12V), either with DC-DC converters, or just by getting separate 9V and/or 5V SMPS's depending on how ambitious I'm feeling. More research needed there, so not something I'm looking to solve in this thread.

Edit: I also realize that a 20A supply is overkill for a ~5A draw, but I might want to add more in future. I might reduce it to 10A total, but again, I'll worry about that separately.
 
Last edited:

ElectricSpidey

Joined Dec 2, 2017
1,868
Do you intend to keep the barrel jacks on the powered devices, or cut them off?

If you are going to cut them off then you need an enclosure and some kind of terminal block such as a barrier strip.

I would suggest leaving them intact and getting some matching panel mount connectors, and installing them in an enclosure.

You can connect as many jacks as you want, just don't exceed the current available on any of the supply terminals.

Leave space inside and a way to connect your DC/DC modules and you are good for the future also.
 

LowQCab

Joined Nov 6, 2012
1,183
It's very likely that all of your Battery-Powered devices pull much less
Current than what the Wall-Worts are rated for.
Actual measurements may allow You to use a much smaller supply,
and with much cheaper/smaller Components.

For instance, anything that runs off of a 9-Volt Battery can use an individual
~1-Amp Linear-Voltage-Regulator Chip to bring the Voltage down from ~12-Volts.

Devices that require a Wall-Wort, and don't have the option of using Batteries,
should probably be sized at the maximum Current rating of the supplied Wall-Wort,
or, the Current Rating on the Specification Sticker on the Device.

I would not advise running anything "in-parallel",
every Device should have its own appropriately sized Voltage-Regulator to
avoid any strange interactions between Devices or the creation of Ground-Loops.

There's a good chance that 1-Linear-Voltage-Regulator part number
will handle everything,
but if more than ~2-Amps are required,
the price of the Voltage-Regulators may start getting more expensive and require
more Heat-Sink capacity.

An SMPS may create too much Electrical-Noise for
directly supplying Audio Equipment, without some well designed Filtering.
.
.
.
 

Thread Starter

benstat

Joined Sep 16, 2021
7
Thank you all!

I had planned to buy some of these and connect the exposed wire ends directly to the SMPS terminals:

1631803765830.png

Then the barrel jacks would just plug into the synth power sockets.

The SMPS has 3 built-in terminal pairs, but I have 4 synths. That would mean 2 of the above wired to the same terminals on the power supply, hence my original question.

If I understand correctly, @LowQCab says I probably shouldn't because that would make it a 'parallel' connection, which can be problematic.

Ignoring possible noise issues for a moment (I'm willing to try my luck if it only costs ~$30), I found this 'Embedded SMPS' which is intended for powering CCTV setups:

1631864505261.png

It appears to have an extra module that distributes DC output to multiple terminal pairs
. Maybe that's the proper way to do it? If so, I'd love to know what that module is called. Can't find anything like it online so far.

Thanks again for your help.
 

Thread Starter

benstat

Joined Sep 16, 2021
7
That's it! Thank you @Yaakov! Now I know what to search for (I was close, but guessing wasn't quite getting me there).

Do you think something like that would solve the problem @LowQCab mentioned?
"every Device should have its own appropriately sized Voltage-Regulator to avoid any strange interactions between Devices or the creation of Ground-Loops"

Edit: And it begs the question, if it's called a "CCTV power distribution block", does that mean it's only suitable for CCTV for some reason? I'd expect something like that to be used all over the place, so why is it labelled specifically for CCTV?
 

Yaakov

Joined Jan 27, 2019
3,565
That's it! Thank you @Yaakov! Now I know what to search for (I was close, but guessing wasn't quite getting me there).

Do you think something like that would solve the problem @LowQCab mentioned?
"every Device should have its own appropriately sized Voltage-Regulator to avoid any strange interactions between Devices or the creation of Ground-Loops"
You’re welcome.

No, that board or something like it provides the same voltaGE on each output. Fusing is a nice feature of it, and some have LEDs to show they ae operational which isn’t a bad thing.

Voltage regulators are small, 3 pin components that take in a high voltage and provide a lower, regulated (stabilized) voltage. Look for LM7809, etc. where the last number (9) is the output voltage. They require a couple of external components, but they aren’t complicated.

You could also use buck converter modules which are more efficient and more expensive but easier because they are already set up, often with terminals ready to go. You will find them for various voltages and in an adjustable form (probably the easiest) all over the place.
 

Thread Starter

benstat

Joined Sep 16, 2021
7
OK, to clarify...

I'll have a regulated SMPS with 3 x 12V DC terminal pairs on it. I'll be connecting just one of those terminal pairs to a power distribution block which will give me, say, 9 output terminal pairs.

So far so good, but (and this is the bit I'm hazy on)...

...the 9 outputs are effectively running in parallel, meaning that they're all reliant on the same voltage regulator in the SMPS. And that's a bad idea because of ground loops and the possibility of "strange interactions between devices" (as LowQCab put it).

Furthermore, I couldn't introduce additional voltage regulators because they take a high voltage and provide a lower, regulated voltage. In this case, the SMPS is 12V and so are all of my synths!

If I haven't misunderstood the above, would I better off getting an 24V SMPS (ie. higher than 12V), and then using 4 buck converters to isolate/regulate each individual 12V output?
 

Yaakov

Joined Jan 27, 2019
3,565
OK, to clarify...

I'll have a regulated SMPS with 3 x 12V DC terminal pairs on it. I'll be connecting just one of those terminal pairs to a power distribution block which will give me, say, 9 output terminal pairs.

So far so good, but (and this is the bit I'm hazy on)...

...the 9 outputs are effectively running in parallel, meaning that they're all reliant on the same voltage regulator in the SMPS. And that's a bad idea because of ground loops and the possibility of "strange interactions between devices" (as LowQCab put it).

Furthermore, I couldn't introduce additional voltage regulators because they take a high voltage and provide a lower, regulated voltage. In this case, the SMPS is 12V and so are all of my synths!

If I haven't misunderstood the above, would I better off getting an 24V SMPS (ie. higher than 12V), and then using 4 buck converters to isolate/regulate each individual 12V output?
You could do that but I am not sure that there is a problem to be solved. I would have to defer to @LowQCab on this if he’s seen problems, but obviously that power distribution block powers multiple separate cameras without special isolation.

You could use 24V and buck converters for each device, it would work, but I am not clear on the utility if the supply voltage is correct already. Again, I can’t really say if it is necessary, I may be missing something.
 

Thread Starter

benstat

Joined Sep 16, 2021
7
I think @LowQCab might have been more concerned with ground loops in my case. It's for audio devices, and ground loops are known to be problematic in such setups because they often result in noise/interference.

I've seen power supplies designed for multiple guitar pedals, for example, where each output is fully isolated to specifically avoid ground loops. I'd use one of those, but guitar pedals have low current, so nowhere near enough amps for my hungry synths.

Anyway, thanks again @Yaakov . Very helpful.
 

BobTPH

Joined Jun 5, 2013
3,769
Ground loops with audio devices is a problem with AC, not so much DC. There will be ground loops anytime you connect two devices together with a signal + ground cable and their power supplies have a common ground. So, just having different regulators coming off the same supply would not fix it, you would need completely isolated supplies.

The reason AC ground loops is a problem is that it puts a “hum” signal on the cable, which then gets amplfied. A small DC offset from one side of the cable to the other does not add any audio.

Bobo
 

Thread Starter

benstat

Joined Sep 16, 2021
7
Ah, very interesting. So I'm back to my original plan then - a 12V SMPS connected to a power distribution block. As long as the supply can handle the load, and I'm careful with polarity, it sounds like it should do the job.

Very grateful for all of your help :)
 

Yaakov

Joined Jan 27, 2019
3,565
When I was building recording studios and video editing suites best practice was lifted shields on the input side of balanced line connections and a solid star ground with a good low impedance path to earth.

If there is no circuitl on the shield/screen between devices there are no loops. Sometimes on unbalanced I/O isolation transformers were necessary but rarely since the star ground was pretty good at making everything equipotential.

[EDIT: Fixed spellcheck error: "fields" to "shields" in ¶1]
 
Last edited:

LowQCab

Joined Nov 6, 2012
1,183
I'm "guessing" that the Synths have more sophisticated Power-Input-Filtering
and therefore should be of somewhat less concern,
but Pedals are notoriously strange.

Generally, if a Pedal manufacturer can leave-out a part, and the device will still work,
then they will almost assuredly leave it out.
So, I didn't mean to make You paranoid about the situation,
I was just trying to bring this to your attention.

Every Pedal will be somewhat different,
some are bullet-proof, and some are a perpetual pain in the butt,
and some will negatively interact with certain other styles/manufacturers of Pedals.

The only way to "guarantee" that there will be no problems caused by Power
is to have a proper Transformer-Isolated, Regulated-Power-Supply for each device.

"Your mileage may vary"
.
.
.
 
Top