M-Audio Thru 1x4 : JeffTadashi's user review
"A simple midi splitter"
The M-Audio Thru 1x4 (which is actually produced by the company's former name, Midiman) is a simple box that takes an input midi signal, and splits it into four midi signals, all though basic midi connections. It required no additional power in almost all cases, as it is a low-powered device that simply powers off the residual power that is present in the input midi signal. There is a red LED that indicates that the Thru 1x4 box is properly receiving power. In some rare cases, you may need to use an additional external power supply with this splitter, if the signals tend to be high power, or if the phantom/active power is not present in the input midi signal. In this case, you would need a simple guitar-pedal like power adapter, but I'm not sure if it's the exact same power adapter, as I've never had a chance to test this feature. This port does run off of 9 Volts DC power, which is the same as guitar pedal power.
This splitter can be a little hard to find, but it is extremely useful in midi applications, specifically if you have a few midi devices that do not have a midi out or midi through. Normally, you can chain all of your devices together with one continuous line, connecting the midi thru of one device to the midi in of the next, and so forth. However, there are several popular midi devices that do not have a midi thru, or their midi out does not function as a midi thru. This was the case for me, with some Line 6 amps, the Digitech Whammy, and other devices. That is where the 1x4 becomes extremely useful, and because it does not need external power, is can be placed anywhere in your midi signal chain.
Overall, this is a great, small, convenient product that works great, if you can find it. Worth every penny!