iGreely DC 5V to DC 9V USB Voltage Step Up Converter Cable 3.3ft/1m Power Supply Adapter Cable with DC Jack 5.5 x 2.5mm or 5.5 x 2.1mm, for Fan, Led Light, Wireless Router, Speakers and More Devices

I purchased this thing to power a guitar pedal from the USB jack on my rechargeable PA speaker which I use as a Bass amp. The fist thing I did when it arrived was plug it in and test the output with my scope meter. It puts out a very flat 9v DC. The output tends to be 1/4v high or low, which I would say is within tolerance. The downside is that, even though the plug is the right size for guitar pedals, the polarity of the plug is backwards and the "adapter" that is included doesn't do anything - it doesn't change the size or the polarity. It would have made sense to include a polarity-reversing adapter, but no, I had to use polarity reversal plug that I happened to have on hand (the red adapter in the photo). Once I got the polarity figured out, I was pleasantly surprised at how well this thing powers my fuzz & octave pedals. There is a bit of RF noise, which I mostly solved by slipping a ferrite bead over the power cord and one over the guitar cord.

This is a center POSITIVE cable. I needed center negative and thought I had looked at that detail, but that was my bad. I needed it to connect a guitar pedal (Zoom G3XN) to a large battery powered Bluetooth speaker with USB output, to be able to play without having to plug in somewhere. I cut the cable, wired/soldered red to black and black to red, reversing the polarity, and it works great!

This item (iGreely DC 9V USB converter cable) is working great for me in powering guitar effects pedals from a USB power bank, after a simple modification that reverses the polarity of 9V DC at the barrel connector. This product (as received, before the modification) provides 9V DC power in a "center positive" (aka, "tip positive") polarity. (In other words, the outside of the round connector is negative, the inside/center of the connector is positive.) This, however, happens to be the exact opposite of what's needed for powering most guitar pedals. So I opened up the USB connector casing to modify it. (See picture - before the mod.) Note that the two halves are NOT glued together but simply fitted together by means of 6 pairs of posts/holes. Thus the casing can be carefully pried open without damage, and pressed back together again after the modification. Using a soldering iron, I just swapped around the connection points for the two wires, before closing the USB connector halves back together again. This simple modification reverses the original polarity of 9V DC into "center negative" needed by most guitar pedals. As far as the size of barrel connector, it should work with most guitar pedals as is - the outside diameter is 5.5mm, and the inside diameter is 2.1mm. (The package I received also contained a little adapter to convert it to OD 5.5mm/ID 2.5mm, which I didn't use.)

I am using this cable & adapter to power several different guitar effects devices. Boomerang 3 looper, Boss ME-80 guitar multi effects, and Zoom G6 guitar multi effects. I use a 20,000 mah USB power bank, and this cable and adapter work fine with all 3 devices. The adapter for different size power jacks made it possible to use with the Boomerang, since it has the 5.5mm x 2.5mm connector; the other devices both use the 5.5mm x 2.1mm.

Doesn’t work for what I have I’m getting a rechargeable pedal power supply to power instead of a standard power bank

The polarity is tip positive, it did not work for me. I need tip negative to power boss Loopstation. :/

I originally got this so I could use a USB power bank to power guitar effects pedals. But the polarity is backwards. So I wound up having to cut the cable, and reverse the polarity. Just somethign to be aware of, in case you're looking to do what I was looking to do.

Wyze Lamp Socket Power Adapter → iGreely DC 5V to DC 9V USB → TP-Link Tapo 2K My house is old and doesn't have any outside outlets; I needed a temporary set up while we had an unexpected hospital stay and I wanted to be able to view the front door. The iGreely adapter casing needed to be trimmed a bit to fit into the Wyze Lamp Socket's USB port but it all is working without issue for over a month now.