Let's say I want to power a Digitech Obscura altered delay pedal. The recommended power supply is a PS0913DC-01.

Now let's say it is impossible to get this specific power supply but we do know the following: It's a 9V 1.3A DC supply with positive exterior and negative interior polarities.

Is this all the information required to know if two power supplies are equivalent or are there other factors to look out for that would otherwise make the device refuse to work properly?

  • \$\begingroup\$ look for customer reviews , so it depends on quality, price, reliability, universal input and selectable output voltages, excess current capacity, selectable plugs and polarity. But centre negative is non-std except in the music industry. This recommended supply is not high quality but works for a while. \$\endgroup\$ Aug 19, 2021 at 12:51
  • \$\begingroup\$ See electronics.stackexchange.com/q/34745/2028. Guitar pedals often require <100mA (an order of magnitude less than 1.3A), but some digital/DSP ones can require 400-500mA. Typically on this site, you would be asking about building your own. If not, the best recommendation for you as an end-user would be to check with a reputable dealer such as your local music store, or one of the online vendors (Andertons, Sweetwater, Thomann, Sam Ash, etc.) \$\endgroup\$
    – JYelton
    Aug 19, 2021 at 15:14
  • \$\begingroup\$ Just a note; comparing two different power supplies from their voltage/current ratings is like comparing two different cars from their make/model. Even though their speedometers might both go up to 150/hr, that doesn't mean both are going to perform equally well at a particular role. It might work, but for how long? \$\endgroup\$
    – rdtsc
    Aug 19, 2021 at 15:25
  • \$\begingroup\$ voltage and current are the only hard-edge criteria you need to consider. \$\endgroup\$
    – dandavis
    Aug 19, 2021 at 17:42

1 Answer 1


In addition to what you can find here : Choosing power supply, how to get the voltage and current ratings?

I would say that the voltage ripple of the output is a criteria.

You will use it for audio applications. Some low cost very noisy power switched mode power supplies may be too noisy for audio applications. You may hear added noise to the audio.

If you buy high end power supplies, you will find graph and figures about the voltage ripple. The ideal goal would be to select a new power supply with a ripple less than, or equal to, the original one. Unfortunately, you can't know the voltage ripple of the "official" power supply... The only thing you can do is to buy one that seems to be better than the average you find.

Another parameter is safety. Your pedal is connected to something that is in contact with a human body. Thus, low cost poorly designed power supplies may be risky to use. I suggest to choose a well known brand, or one that is meant for medical applications. It may be overprized, but my safety has an even higher price....

  • 3
    \$\begingroup\$ Basically: buy products that are legal. If you shop cheap crap from Ali Baba then you don't necessarily get products that are legal in your/any country. \$\endgroup\$
    – Lundin
    Aug 19, 2021 at 13:04

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