SUMMARY - if you want to switch between two instruments into one amp, (like 2 guitars ) this solution is pretty much ideal and works very well. If you are switching between amplifiers, you can find better solutions that will potentially be more noise-free, and potentially safer, but they cost more money. Overall, I really like the A or B, A and B switching layout and functionality. This also uses a 9V battery OR a 9V power supply. Prior reviews criticizing lack of easy access to the battery and lack of a 9V input jack are no longer valid -- the product was updated to add an easy access battery door and a "standard" 9V jack so you can easily run from your favorite power supply. And the price is right. This is FAR better than the Boss AB-2 that is in the same price range. It lacks a few features that are especially helpful when using this to switch between amplifier inputs.