Concerns when buying power supplies

[asmith]

I searched for existing threads covering this issue, but couldn't find any.

I own seventeen effects pedals, and I'd still like more. I attend meetings, but they aren't working. Most of the pedals I own are 'analogue' effects. A handful are 'digital'. One of the pedals is an EQ that requires 18 V and draws 48 mA. The rest require 9 V and draw various amounts of current.

I'm looking at buying two 10-output power supplies for the pedals. I'm aware that many consider output isolation an attractive feature, as it reduces noise. I'm also aware that many power supplies 'top out' at a maximum amount of current drawn.

These rough ideas are the extent of my knowledge. Can someone explain the science a little more in-depth to me, and use it to inform me about what concerns I should have when purchasing the power supplies, so that my purchases can be better informed?

[thetragichero]

I've had good results with those dirt cheap (caline, etc) supplies you can find everywhere

my own personal board uses an old laptop power supply (from a long discarded laptop) and half a dozen linear voltage regulators (one 12v and the rest 10v to provide 9.81v like a fresh battery) along with a bunch of caps. it originally was just one 12v and one 10v regulator but i was getting noise. so not transformer isolated like the expensive supplies claim but the isolation from the regulators is helpful. i still use some daisy chain cables because i have more pedals than supply taps

basically it's not as serious as a lot of the gearheads make it out to be and a lot of folks are using grossly over-engineered supplies

[JohnH]

My home board is my whole Digitech Hardwire collection, plus a couple more, 5 in the fx loop and 6 in front. I run them on a single daisy chain from a Roland 2A supply designed for audio stuff all 9V. This works fine with no noise. But I tried other non-specific stabilised supplies designed for similar current and got hum.

[mikecg]

Hello asmith,

With reference to the thetragichero 's comment on the cheaper multi-output, isolated supplies, here's a link to the 'Caline' products he mentioned:

www.calinemusic.com/index.php?m=home&c=Lists&a=index&tid=31

As a rough guide, the Caline CP-207 model with 10 isolated outputs sells on Aliexpress for around £20.

Note that some of their earlier/slightly cheaper models such as the CP-04 do not appear to have isolated outputs, and as the models with isolated outputs are only marginally more expensive, my advice would be to 'go isolated'.

There appear to be a number of similar products on offer - but I hasten to add that I can't comment on their performance, or durability, as I don't have one, myself.

Properly isolated outputs can help to prevent ground current loops in the 'network' of pedal board connections, induced by electro-magnetic fields from local ac power lines. These ground loop currents, can produce 'series mode' noise at the fundamental, and harmonic of the ac power frequency (hum), in unbalanced audio cables.
A 'single point' grounding scheme is another way of minimizing these 'loop currents', and the corresponding 'hum' levels.

[mikecg]

Addendum: Unfortunately, the detailed specifications of the 'Caline type' power supplies are a little vague when it comes to their definition of 'isolated'.
My guess is that their definition could simply mean that each output has a separate current limit circuit, so that in the event of an over-current or short circuit on one output, then that output is protected (fold back current limited?) and 'isolated' from all the other outputs, that will continue working normally.
There is no specific mention of ground isolation between the multi-outputs, and that is, IMHO an important omission. Caveat emptor!

However, I have found one product that does appear to have 'ground isolation' in its specification, the MOSKYaudio ISO10:

 
www.moskyaudio.com/product/product-19-230.html


(These sell on Aliexpress for around £30)

[mitch88]

Beware DickSmith power supplies (items in general) as the business is defunct and Tech Support is non existant by email and fone.
I bought a 9V power supply with multi tips but packaging or items DID NOT STATE wether tips were centre +'ve or -'ve, and several attempts to contact DSmith in various ways was either a brick wall or an email "we dont do Tech Support, see retailer".
Incorrect centre polarity can damage the item being powered = expensive repairs!!

[thetragichero]

mitch88 time to bust out the multimeter and see for yourself

[mitch88]

Thanks, I dont have one.