I am using a 9V AC converter for a digitech product. But I notice that there is a pin in a socket kind of thing in the adapter. What is the use of this pin?

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  • \$\begingroup\$ What does the manual say? \$\endgroup\$ Commented Aug 30, 2014 at 5:50
  • \$\begingroup\$ Could not find the specification for it. This is the product. digitech.com/en/products/ps0913b \$\endgroup\$
    – Tanmoy
    Commented Aug 30, 2014 at 5:56
  • 1
    \$\begingroup\$ Based on the link you provided, it appears the adapter has a normal cord with a DC plug (but remember, it's an AC adapter; just the plug type is called a DC power plug) on the end, so this jack is in addition to that cord. I couldn't say if it is some sort of duplicate (wired in parallel) or if it serves some other function, like testing for quality control. You could use a multimeter to check it out. \$\endgroup\$
    – JYelton
    Commented Aug 30, 2014 at 6:00
  • \$\begingroup\$ @Tanmoy This input jack on an AC to AC wall wart looks odd. I think, you have the following options. (1) Open the case (which may or may not be worth it) and post the picture of the inside of the adapter, or draw a diagram. (2) Mirror this question of yours at the DigiTech forum. They have their own community/forum. Or, e-mail their support. \$\endgroup\$ Commented Aug 30, 2014 at 6:11
  • \$\begingroup\$ Silly me. It is actually written at the back of the adapter ... the main output is 1.3A and the pin output is 0.1A \$\endgroup\$
    – Tanmoy
    Commented Aug 30, 2014 at 6:32

1 Answer 1


That looks like the center pin of a standard DC Power Jack (also known as a barrel jack).

Edit: Note that this is just the name of the type of connector, so if your adapter is an AC to AC adapter, it still supplies AC.

The inside of the jack makes contact with the outer contact on the plug, while the pin makes contact with the inside of the plug.

DC Jack:
DC Jack

DC Plug:
DC Plug

They are available in different sizes and diameters. There are lots of related questions you might find useful:

  • \$\begingroup\$ Does it mean the same adapter can be used as 9V DC adapter as well? \$\endgroup\$
    – Tanmoy
    Commented Aug 30, 2014 at 5:43
  • 2
    \$\begingroup\$ @Tanmoy No, the name of these jacks is just typically "DC" but it doesn't mean that they are carrying DC. If your adapter is an AC to AC adapter, then it is supplying AC even though it utilizes a DC jack. Good question. \$\endgroup\$
    – JYelton
    Commented Aug 30, 2014 at 5:58

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